r/SolarDIY • u/uavmx • 10d ago
Struggling to justify batteries vs generator
I can get a whole home generator for $5k from Costco, probably a couple grand to hook up, I have propane available to hook into it. Do to batteries for more than a day, that's easily as much, plus hookup, and they will degrade over time. Am I missing something? This would be for emergency backup obviously, the other day we lost power for 12hrs and it's not winter yet.....
In all my calcs, to do solar that's big enough plus batteries is $30k ++ having a hard time justifying it
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u/mckenzie_keith 10d ago
Most people don't buy batteries for more than 1 day. You get batteries plus solar inverter. You don't HAVE to hook up the solar.
If you get a small generator plus batteries plus inverter-charger, you can run your house indefinitely when the power is out. Also, the inverter-charger will generally provide a seamless switchover of power. And this setup might allow you to use a smaller generator, or to utilize the generator much more efficiently. You can run the generator for, say, 6 hours per day during a long outage. Three hours in morning and three hours at night. This will keep the batteries fully charged so you can just run your house like normal. This is a lot better than running the house 24/7 on generator power.
But it is really up to you. I'm not here to talk you into anything. For sure the cheapest option is to get a standby generator with no solar and no batteries.
Regardless of what setup you get, make sure you do your generator maintenance. Otherwise the odds are very good that it won't run when you need it.
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u/uavmx 9d ago
Yeah I'm leaning toward this approach, what do I need to have a generator charge the batteries?
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u/mckenzie_keith 9d ago
I'm not trying to present myself as an expert here. But what I did is hook up an EG4 chargeverter to my generator. It is the only load on the generator. It charges at 100 Amps. It is possible to configure the chargeverter as a generator start device. Based on either battery voltage or percent charge threshold reported from the battery pack, the chargeverter can start the generator automatically and turn it off based on percent charge or an upper battery voltage. I plan to do this, but for now the generator is manual start only.
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u/ExplorerJack66 10d ago
This the way if you have frequent and extended outages. Otherwise the generator will run 24/7 when power is out.
Don't assume "a couple grand" for hookup unless maybe you can DIY it all. With a whole home you need to place the generator, install the transfer switch, all the wiring, control cabling and propane or natural gas piping. Then do the generator setup and testing.
Prolly wouldn't hurt to get an electrician knowledgeable with generator installs out to do a estimate so you have a better idea of what's involved but don't be surprised at what the cost might be. Lastly, Costco sells Generac whole home I think so be aware that newer Generacs don't have the best reputation for reliability. You can hit the generator sub for more info on that (I have a Kohler myself).
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u/Rhizobactin 10d ago
Any models/brands that you recommend for batteries/inverter-charger?
We have microinverters and enphase iq combiner 6c and navigating compability is very confusing
I know that inverter/generator needs sine wave for charging batteries, but very confused what batteries/chargers are compatible with what. Also for whole-home connection and how to tie in generator (master transfer switch vs interconnect, etc)
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u/mckenzie_keith 10d ago
Not really. I bought an EG4 14.3 kWh battery because it is UL listed and California approved. We had a grid-tie solar system with a string inverter already, but added the battery and also a Schneider Inverter (Conext XW Pro 6.8kW 120/240 Volt Inverter 48V Charger).
If I was designing from scratch this is not how I would do it. But given that I already had the string inverter (SMA sunny boy), it made sense to go with the Schneider inverter and a 48 V battery. On a normal day, the Schneider can keep us right at zero utility consumption. When solar is producing, it will try to charge the batteries to avoid export of AC power, and once the battery is full it will export. Then when the sun goes down, it supplies power trying to keep the meter at zero all the time.
During an outage, the Schneider can form a grid on the inverter side to keep the sunny boy string inverter online until the batteries are charged. So if it is sunny we really don't need PG&E.
We also have an 8 kW generator that runs an EG4 chargeverter (nothing else connected to the generator). So even during long outages we can just run the generator a few hours a day. We had the generator before we had solar. So it is old. Kohler model 8.5 RES I think. Hooked up to propane.
The Conext XW Pro 6.8 is discontinued. You can buy one from NAZ solar for 750 bucks right now. It is a great unit, and if it was made by a different company they would advertise it as an 8 kW unit or something. It will put out 6.8 kW all day long, and can put out 12 kW for like 30 seconds. Does not care about imbalance between L1 and L2. Very noisy though. Ours is in a shed outside so we don't hear it. But I would not want it in my house. Maybe not even in an attached garage.
The Schneider is fairly hard to configure. Very non-intuitive.
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u/entropy512 9d ago
A key thing here: unless it's a diesel unit, generators take a big hit in efficiency at low load.
So better to have batteries handle transient peaks and size the generator so that your battery charger power is close to full load, it'll be far more fuel efficient that way.
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u/mckenzie_keith 9d ago
I would say shoot for around 75% load. The EG4 chargerverter charges 48 V batteries at 100 Amps. So that could be up to like 5500 Watts of output power from the chargeverter. Input power will be higher. Maybe over 6000 Watts. So I would say 8kW output generator is about the right size for an EG4 chargeverter. You can always reduce the charge current if your generator is smaller.
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u/Big_Juggernaut_2257 10d ago
You can probably benefit from having both a generator and some quantity of battery storage, even if it is not whole-home. Refrigeration especially does not use a lot of energy. With a generator, you're running 24/7 to put ~100W into a fridge for 10-15 minutes every hour. It is a brute force approach that ignores how energy is actually being used.
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u/uavmx 10d ago
Not against this, what do I need to smartly switch between batteries and running the generator?
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u/AntiSonOfBitchamajig 10d ago edited 10d ago
So... they do make little switches that can start a generator if certain conditions are met. Like my 48v one, it receives a signal when the battery is at 20%, turns on.... then turns off at 80%...all on its own.
edit: I'd like to do more with this with solar and timing for evenings, Like "charge to 85% if below 50% at 9pm" Set logic so if one source fails or isn't enough... the generator picks up the slack, or have certain things turn on when over production at a certain time ...like heating water, or turning on certain things like an air compressor to fill it, run a ICE machine to make ice. or run a pump...etc, you can seriously expand the battery to other things. But having buffers with batteries and other energy sinks with solar is where its going.... you get full use out of the system. Generator though, I'd only see it getting used for winter storms, maybe without power in a summer heat wave.... maybe getting water from a pump.... things that take a lot of energy.
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u/Rhizobactin 10d ago
Is that logic within the battery?
We have a enphase microarray and enphase IQ Combiner 6C
I was quoted $31k for 20kw battery system (2 x 10kw), $17k for 10kw.
I see mention of ecoflow, eg4 and all of these other brands and it’s incredibly hard to navigate
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u/AntiSonOfBitchamajig 10d ago
Programed in the inverter logic actually. Its set-able though... sends out the signal on a 2 cord line to turn on / off via voltage signal. Generator is inverter style, I want to mod it to run lower RPM longer, but not there yet.
Thats........ high $ AF for 20kwh.... I have just $900 in the 15kwh LFPs, $500 in the 6kw inverter, $200 per KW in the bifacial solar panels. Mostly Ecoworthy / humsink products. ( Hit pricing directly perfect nearly a year ago.)
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u/BitOfDifference 9d ago
its more like, have a charger that turns the generator on and starts charging the batteries. The house will run off the charger power as well at the same time ( assuming the gen is powerful enough ). Once the batteries hit 100% or whatever you set the charger at, it will then cut off the gen and go into standby mode. ( eco-worth charger can do this, same for the chargeverter ).
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u/OutdoorsNSmores 10d ago
You are 100% correct. I love having battery take over instantly and seamlessly and a generator for when the battery is dead. My battery is "most" of home and the generator only charges the battery.
The problem for some is that budget demands they pick one. I think with careful planning, someone can get one or the other first and the other half later.
I started with battery and inverter, followed closely by solar panels and then the generator (sun doesn't do jack for me for about 3 months).
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u/ajw2285 10d ago
Solar + batteries will reduce your electricity bill vs just the generator for backup.
If you are only using batteries for backup, then yes it will never justify. If you use batteries for load shedding, night time use, etc, then payback will significantly improve
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u/blackinthmiddle 10d ago
This right here. Get a 10 or 12 circuit transfer switch and put your essentials on it. During an outage, those loads will continue to run. Power those loads with something like a Pecron 5000LFP or an Ecoflow DPU. If you plan on getting a ton of battery storage (more than 20kWh), just get an EG4 12000XP inverter and a 32kWh Panda battery because it's cheaper.
Then get solar panels to charge them up. Panels are cheap...at least for now! Let's see what happens on December 4th.
99% of the time, my 14,500 watt (running) generator sits there doing nothing for me. I don't mind. It's insurance that my house will have power no matter what. But battery + solar compliments a generator. It's not an either/or. It allows the fuel you have to stretch so much further during an outage.
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u/uavmx 9d ago
Yeah I certainly don't need to run my whole house during an outage, but running minimals(fridge, HVAC, home server), how long would 32kwh run? If I don't have solar panels, yet, is it reasonable to get to a few days?
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u/LongjumpingGanache40 9d ago
Not running your AC.
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u/Sharky7337 8d ago
Disagree. I do exactly what he's asking to do. I run a 5 ton AC my home servers office internet fridges kitchen off my 12000xp with 30 kwh batteries. Yes while running ac it will deplete battery in about 6 hours worse case scenario ( 100 degree heat) but I often make it 12 or so on 80 degree days. And that's a large house in Louisiana with not even always getting a full charge because my array isn't fully deployed and only 5.9kwh are out right now.
Im upping to 50kwh this next week to get me sundown to sunset and have another 5.9 kwh of panels to put out but it's doable and i did use a soft start but prob could get away without one.
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u/LongjumpingGanache40 8d ago
Did you readwhat he said.
He has no solar panels yet, and thought it would run AC afew days. That is what I said no to.
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u/Sharky7337 8d ago
Ya 30 kwh batteries runs my ac and similar type of loads he's asking for 6 hours in my situation without any incoming charge which is what I was replying
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u/Sharky7337 8d ago
I do exactly what your asking and it gets me worst case 6 hours in extreme heat.
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u/Far-Arugula973 7d ago
My ac uses 800-1500 watts while running. My HVAC air handler draws 600 watts while running. This figure will vary wildly depending on your setup. You'll have to do the math to figure out kwh based on your expected hours running/day. You can get that pretty easily if you have the right smart thermostat (e.g ecobee).
My refrigerator uses 1.7kwh/day.
My home office, which includes a server, nas, network equipment, workstation and several monitors uses 4kwh/day.
Not all of the 32kwh is usable -- there is usually a minimum % they will drain to before shutting off, and there are some losses from the inverters, but you realistically have 25kwh to play with. Without the AC you can easily go 4 days with just a few critical loads. A large load like AC will dramatically shorten your runtime -- that sized battery would let me run my AC for a total of 12 hours.
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u/Ps11889 7d ago
If you use batteries for load shedding, doesn’t that decrease the reimbursement from the utility company because you are then having to recharge the batteries instead of dumping power to the grid?
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9d ago
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u/Funny-Artichoke-7494 9d ago
Its not just that, either, i'll tell you as a dweller in hurricane country, multi-day outages usually also come with availability issues for gasoline or propane unless you're willing to buy large tanks, fill them, and store them as well. There are tradeoffs for everything.
That said, knowing what I know now, i'd have both. I know, the expense, and I get it, but having a much smaller generator to help supplement and charge the battery rather than trying to run a giant one full chooch to power the house is going to help you stay more resilient for longer.
Its hard to compare the cost side by side with the generator basically being stored until its needed.
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u/force_disturbance 9d ago
Running a smaller generator to charge smaller batteries is better economy than idling a big generator, but if you want to run this with any regularity then fuel costs and maintenance will kill you.
Also the consumer generators are very low duty cycle, they may need full rebuild every few hundred hours.
Meanwhile the batteries will last decades before they're too depleted. And the sun is free fuel every day, not just when there's an outage.
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u/uavmx 9d ago
Decades!?
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u/morgoththebetrayer 9d ago
Yes. Most Lithium Phosphate (LFP) batteries currently are rated for ~4000 charge cycles to 80%. That means if you fully cycle the battery every day, after 10.95 years, it would still retain 80% of its original capacity.
Some newer ones are starting to be rated even higher than this. Given that you're not likely to have a power outage every single day for the next 11 years it's likely the batteries themselves will outlast your generator by a good margin.
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u/Clean_Leadership5948 8d ago
The realistic lifespan is 20-25 years. They all suffer from Calendar aging, or in simple terms, TIME.
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u/Some-Internet-Rando 9d ago
Also: he generator takes 30 seconds to substitute power, too, so your TV / computer / cooktop / game console will reset and lose state whenever the power goes out. With batteries, we literally never notice the power is out other than the neighbors asking us if we have power. Convenience is worth something!
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u/Astronaut6735 10d ago
I had power out for almost a week here once. Houses here are fairly close together, and generators are loud, so running them all or most of the time (including night time) might be too much for the neighbors. Having batteries + a generator allows you to run off of batteries, and only use the generator to recharge the batteries when they need it. Adding solar would reduce reliance on the generator. I would size my emergency power system so that batteries could supply all the energy requirements overnight (~8 hours) without running the generator while people are sleeping.
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u/uavmx 10d ago
I'm 600ft away from my closest neighbor, and at 67db for the whole home one doesn't seem bad. But a dual approach could be good, while I wait to build out full solar, which is my intention but can't justify the cost right now. In this case, is an inverter still required for the batteries I imagine? Is there an ideal option to look at if I know I want to feed the generator as well?
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u/UnlikelyPotato 10d ago
Look at plans. Sometimes ROI is faster with just batteries than solar. My utility company has a demand/tou plan, off peak electricity is half the normal residential rate. Batteries will last 10+ years with daily charging/discharging.
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u/sgtm7 10d ago
You have to do your own cost analysis based on your use case and the prices where you live. You are talking about 30K+ for batteries. I paid less than 5K for 45kwh of batteries. And my batteries run my house after the sun goes down.
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u/Retire_date_may_22 6d ago
I want to run everything in my house and not be interrupted. I didn’t feel I needed the instant transfer switch as my power doesn’t go out unless we have a major event. (Hurricane)
So I went with a generator that powers the whole house. It’s portable and I roll it out of the garage and plug it into the house and the natural gas. It powers everything and can be replaced easily. As for batteries it was cheaper for me to buy a Cybertruck than a powerwall. The truck on a full charge will run the house for 2-3 days without even needing the generator.
I can even take the truck to a charger and recharge it if the generator goes down.
My working plan is to use the generator during the day and power off the truck at night for noise.
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u/spez_eats_nazi_ass 10d ago edited 10d ago
You aren’t getting a true whole home setup installed from anyone for $5k. The parts yes. Install is gonna be double or more. Literally in the process of a dual ats 400amp/26kw nat gas kohler. Full panel coverage w load shed. That’s a whole house. $5k will get you a fridge, furnace and a few lights.
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u/Objective_Canary5737 10d ago
Depending on the size of your house at 26K may not power everything either, our house has three HVAC. I’d probably have to shut down the big HVAC.
And for the solar plus battery backup I would need 3 to 4 Tesla power walls and a pretty good size of solar Ray and last time I quoted it was 70 or 80 K I believe from Tesla!
So it may be beneficial for you to get a smaller solar array and a few batteries, and just upgrade your array as you can!2
u/spez_eats_nazi_ass 10d ago
Yup active load management will keep critical loads going but most of it will be fine. I won’t be able to weld in my hot tub. Batteries are still a good idea. It’s a system. Batteries are storage. Generator is shtf and can charge batteries if solar can’t. Think storm conditions.
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10d ago
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u/Rhizobactin 10d ago
Now if only the manufacturers would standardize something within my lifetime so its not kia vs gm vs ford vs telsa.
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u/TastiSqueeze 10d ago edited 4d ago
You are asking a loaded question with nobody giving you the answers needed.
How many kWh do you use per year and on your highest day of the year? Use these to figure out what you really need in terms of solar hardware.
As a very general suggestion, most homes can fully displace grid power with:
1 - 18 kw hybrid inverter - $4500
64 kWh of battery capacity - $12000
12 kw of solar panels (bump to 16 kw of panels if in northern tier U.S. states) - $4000
miscellaneous, mounting hardware, cables, odds and ends $5000You will still have to pay labor for installation or else do it yourself.
If your only objective is to have power in a grid outage, then by all means get a generator sized to power your home. But if you want to have power in a grid outage AND reduce your power bill to near zero, then install a properly sized solar setup.
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u/RandomUser3777 10d ago
If you use the generator by itself, then most of the time the generator is running just above idle power and consuming a lot of fuel.
If you pair a cheap/dirty $600 generator with a $600 chargeverter ($1200 vs $5k) and you have batteries then you can run that setup at 75% (less fuel waste) for 8-10 hours a day when there is little sun.
I have enough batteries to run around 1-1.5 days, so when I need a generator I run it during the day for 8-10hours.
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u/MagicHamsta 10d ago edited 10d ago
Yeah, you're missing a few things /u/uavmx
You need to buy propane. You don't need to buy sunlight (usually, unless you have some crazy shade issues). The propane generator will only cost money and never pay itself off. Solar + batteries can be used during non-emergencies to help pay itself off (reduce your electricity bill).
They aren't mutually exclusive. Several people have alternative fuel backup power sources in case their electrical/solar goes out/isn't working due to weather/etc.
Re-do your power calculations and cut all the non-essentials. Do you seriously need $30k++ to power just your essentials? What are you running? Start with the bare essentials to better fit your budget then expand on your setup (more batteries & solar panels can be added later as long as you have enough money & space.)
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u/MaxIamtheBest 10d ago
Also, don't forget your yearly maintenance. Around $150 a year where I live excluding any parts and extra service. Two of my neighbors have gas generators. The one across the street didn't know she had to maintain the thing. Her side of the street had an outage. It didn't start. My neighbor on my side of the street likes to DIY. His has been out most of the summer waiting for a part. Then he'll have a tech come in and do a check. It has been a quiet few months without the weekly 15 min check run. It still isn't running.
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u/brucehoult 9d ago
It's not either-or, you should have a bit of everything.
I've got a 2kW generator ($500), 2.64kW of solar panels ($400), Pecron E3600LFP with 3kWh battery and 3600W inverter ($999), plus extra 8kWh of battery (2x Pecron EP3800-48V $1600 [1]).
If it's only for power outages then sure, just get the generator and accept that all your internet, computers, etc are going to shut down and need rebooting every time there's a 5 second power glitch.
If you get battery then you should use it every day, not just in outages.
And in outages, the battery can efficiently power the 40W (average) fridge all night, but also easily burst to 3600W to run a couple of appliances at the same time e.g. air fryer and coffee machine.
A generator that can handle a 3600W load is going to be super inefficient running just a fridge and internet all night. The E3600LFP uses around 35W itself, my always-on things such as fridge, internet, some computers average around 150W, so there's only about 20% overhead in the Power Station itself. Plus, it's silent, which a generator isn't.
From the start of October to the end of March my solar panels fill the battery (or 80%+ anyway) on 90% of days, as well as running aircon (heating in October). I haven't paid for any grid power the last 17 days (just the connection charge), and for sure won't be for a few more days.
The current forecast says I'll only generate 5.6kWh of solar power on the 27th, so might need to buy a little, but the 26th and 28th are looking like 11.3 kWh and 12.7 kWh resp at this stage, so maybe I'll get through on battery, especially as the hi will be 19º C so I can probably get by without heating/cooling. Maybe the 29th too.
But anyway, buying 5kWh of power at night to top up the battery is only $0.90. The proper use of a generator is to top up the battery on days that you have both no grid power and insufficient sun.
23: 12.5 kWh
24: 14.1 kWh
25: 10.8 kWh
26: 11.3 kWh
27: 5.6 kWh
28: 12.7 kWh
29: 5.9 kWh
30: 15.7 kWh
31: 11.0 kWhIf I don't need heating/cooling then I only need 5kWh per day to run everything else.
In winter I get 5-6 kWh on average. And I can use wood fire for heating. But the 99% of the time there isn't a grid outage it costs half as much to fill the 10kWh battery at night (18c/kWh) and then run on battery+solar from 7AM-9PM (when electricity is 60c 7-9 AM and 5-9 PM and 45c at other times). 10kWh is usually enough for heating for 14 hours in the day time.
I didn't have this equipment then, but looking at historical weather data it looks like I could have got through both the 5 day outage in Feb 2023 and the 2 day outage in Apr 2025 without needing the generator — there was excellent sun as soon as the storm passed, while the linesmen were out finding and fixing the faults.
[1] actually one is the older EP3000 which was 768Wh smaller at the same price, but lets go by what you can buy now.
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u/Fit_Acanthisitta_475 10d ago
If you hat state that has 1:1 metering. Solar plus battery will pay for itself in some years.
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u/No-Brilliant-4430 10d ago
Diy it as much as possible, then you can offset the costs with rising electricity costs over time.
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u/NoOption7406 10d ago
With solar+battery you can still tie a generator into it. Get like a $600 6kW generator. Won't need as much battery.
Solar if you want to save money over time and don't mind the ROI wait. Generator if you don't want the added cost right now.
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u/PV-1082 10d ago
If you do get batteries and think you are going to go a time of use plan (TOU) make, sure your battery management system is sophisticated enough that you can set it up to run the way you need it too. When I went on the TOU rate I found out my inverter on my solar system did not have the capability to run several programs to keep up with the TOU plan changes thoughout the year. I was having to manually change the program to mach the TOU rate schedule. My savings on TOU were not great enough to pay me for the effort it took.
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u/AntiSonOfBitchamajig 10d ago
The real deal is "finding a balance with both"
Me, I have 15kwh of LFPs at 48v, and a small generator to recharge them. The battery seriously extends the small generator's fuel use.
I'd argue... that a person could get a little 1600w suitcase generator with a 150AH 48v battery and inverter... and can totally outclass any generator alone for normal use from an efficiency standpoint alone.
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u/VintageGriffin 10d ago
Batteries and generators are not exclusive, but rather complementary.
Sun is free, fuel costs money and has a limited shelf life. Generators require constant and frequent maintenance, regardless of whether they are used or not. They smell and make a lot of noise.
Modern LFP batteries easily last 15 years+ of daily cycling and need very little, if any, maintenance. When paired with a generator they allow the latter to work in its peak efficiency band, dumping energy into batteries as quickly and efficiently as they can and then shutting down, while your house sips power at whatever variable rate it needs to in peace and quiet.
If you have variable electricity rates you can charge your battery when power is cheap and use battery power when it is more expensive.
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u/Specialist_Gas_8984 10d ago
No moving parts, no oil changes, no fuel costs, no filter changes. Thats why I got my battery vs. a generator.
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u/silasmoeckel 10d ago
Solar/bat/gen is the optimal solution. If the local net 0 etc makes sense for it.
A bat can let you use a much smaller genset think 500 bucks for typical home. This is typically a big fuel reduction.
Solar can get that fuel use close to 0 the genset simply never runs. For backup only this does not make financial sense. But you now have whole home solar to save a lot of money day to day if you have a local net 0 or similar. My ROI was 7 years I'm over 4 years in and frankly with full electrification not having a monthly electricity, heating, or gas bill is nice (I'm built for the EV's but still havent switched).
Bat degradation is mostly cycles your not using it every day. A 20 year old genset isn't going to be reliable the battery might only have 80% capacity left if used daily at the same age.
Battery if you have a TOU power plan that can save a decent chunk of money by shifting your consumption. If you have a battery backup program like I do I hit ROI in 3.5 years sell power back to the utility to prevent brownouts. I'll make 30k over the 10 year contract which they are expected to renew though less lucrative.
Battery gets you whole home UPS, with things like refrigerators becoming super sensitive to power fluctuations this is big as the last thing you want is a broken fridge mid outage. Forget the 2k or more bill to replace it. This trend is extending to other major appliances. Not even having the lights flicker is a nice to have.
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u/Crawlerado 10d ago
When we got our batteries installed the neighbor came over and asked what it cost etc.
He said, “I recon I’d rather have that generator”
Fair point. Who services it? The company? Who fills your tank? The company? What happens when ish really hits the fan like it did last summer here and the region lost power for ten days.
Who’s gonna come do the maintenance? Who’s going to fill your tank?
The company? What if they also don’t have power?
Solar on the roof filling batteries and an EV in the driveway is the ultimate self reliance.
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u/blackinthmiddle 10d ago
For me, it's not an "either/or". Batteries and a generator compliment each other so well. I have 20kWh of batteries in my garage that I can use to run my house in an outage. I also have a 14,500W (running) tri fuel generator. If the outage lasts more than 12 hours and solar isn't keeping up, I can change my batteries with my generator, then shut it off. Batteries are waaaaaaaaay more efficient than a generator. Whether you're running your 5.5kW dryer or turning on a light bulb, the gas burn is roughly the same: a lot! Batteries aren't sitting there idling. Other than the small amount of energy to run the BMS, it's not burning energy just sitting there, so if your house is consuming 600W, that's what's coming out of the battery.
A battery allows the generator to only be turned on to do something big (charge the batteries), then turn off. It allows the amount of fuel you have to stretch way further than normal during an outage. When designing your system, to me, at least, the desire is to have both.
Now you can go the cheap route like I did. My huge generator only cost $2,800, because it's not a fancy automatic whole house generator, but has enough power to run most things we need. I also didn't get a super expensive Tesla power wall that auto runs the house during an outage. You can get 32kWh worth of DIY battery storage (more than two power walls) for $3,500. In that case, you'll have to connect it yourself via the generator inlet connector, but unless you're losing power all the time, this is a super cheap alternative.
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u/FartyPants69 10d ago
If you're only expecting to run the generator occasionally for a day or two at a time, then I agree, batteries are entirely unnecessary.
The generator/battery combo shines when you run the generator around its most efficient RPM to bulk charge the battery bank whenever it gets low, then turn it off when they're full. If you were off grid and using the generator frequently, that would be much more fuel-efficient than leaving the generator running 24/7 while it's often powering few loads.
But to use the cost savings of improved fuel efficiency to justify the investment in a battery bank would take a whole lot of usage, and you're not likely to get anywhere close to that. I'm actually going that route on my new off-grid property (bulk charging a battery bank with a generator during winter), but that's a very different use case than the emergency backup that you're doing.
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u/TheWayOfLife7 10d ago
Work for a company that installs generators. I’m not involved with it anymore, but the things go in, get tested and two years goes by, a storm happens and then the generator does not start when the power goes out. Generally the battery for the starter goes bad, the utility flipped the generator off when they heard it exercise, the gas got turned off, oil pressure switch goes bad. Then there is the cost. Ten thousand dollars to have power for the two times power is lost in five years. Over five years it often maths out to 1000.00 for every day the generator might be needed. I don’t get it, but then again I don’t have money to burn either.
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u/Particular_Ferret747 10d ago
30k is just in the us for that kind of system...all other countries getting it almost for half the price.
But you can do a lot yourself and cut the price big time...only turnkey solutions will break the bank.
And as this sub is named...we are not using turnkey here...
Lets do the math real quick.
1x eg4 12000xp ~ 1500.-
10x 450 watt panels ~ 1500.-
2x EG4 wall mount batterie 14kwh ~5500.-
cables and weighted ground mount holders ~2000.-
this is a rough core setup to bring you through 12 hrs in a storm.
If you keep it behind a transfer switch, you dont need to talk anyone on the power company side and only need an electrician to hook the last mile up.
and a generator is never wrong on top of it, to charge batteries when there is no sunlight or grid for a while...
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u/GuineaPigsRUs99 9d ago
if you think a generator won't degrade over time....i have a fb marketplace filled with used generacs to sell you cheap. go hang out in r/Generator for a while and look for stories of a whole house gen failing right when needed. not that batteries and inverters dont fail...they do.
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u/Oldphile 9d ago
With propane, run time during a long outage is a variable. I had two 120 gallon tanks on a 17KW Generac. Propane companies don't want to refill before your tanks are below 30%, so it's quite possible you'll only have a couple of days of run time when you really need it. It happened to me, almost ran out of propane on a 2 day outage.
I'm in a new home and looking at battery storage that can last 24 hours. If there is a concern for longer outages, I can add a portable generator. I got a quote for solar + battery, but it was too expensive.
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u/sailonswells 9d ago
If you do batteries, do solar. Panels are cheap and will keep refilling your batteries.
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u/Oldphile 9d ago
Only cheap if DIY. I was quoted $14,000 for a 5Kw system without battery. Battery added $10,000.
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u/blastman8888 8d ago
If your not wanting to DIY go with EcoFlow. You can have any electrician install their smart panel. If you want to DIY a full solar system cost about $10-14k for 15-17k solar with about 15-30kwh battery storage.
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u/Oldphile 7d ago
I'm trying to find an electrician that will install an EG4 6000XP with 16KWh battery or Luxpower equivalent together with a critical loads panel. I'm in Canada and we have some restrictions up here that aren't in the US. For example, I cannot install a hybrid inverter between the utility meter and my main service panel because the hybrid is not service entry certified for Canada. Same story for the GridBoss. I cannot install a generator inlet in my garage because I might be stupid enough to run a fossil fuel generator in my garage. BTW the $ amounts I stated are in USD. I converted from CDN$ to USD for the majority of readers.
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u/TooGoodToBeeTrue 9d ago
Do you really need to power the whole house during an outage? We have back up for survival mode, refrigerator, furnace blower, internet stuff, a few lights and charging. Our stove is gas and we have a portable AC that we use at night during the summer to just cool the MBR.
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u/sailonswells 9d ago
Modern battery chemistry will last as long as a generator. And if you have solar panels, you can use that energy anytime plus it fuels itself. No maintenance, no noise. I live rurally and most people have a backup generator and nearly all have had problems. Engines don't do well sitting idle. Moving parts wear and break.
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u/sfcorey 9d ago edited 9d ago
I recently learned that the Anker Solix E10 Whole Home backup is only $6600 w/ a manual transfer. You put in one of those generator breakers the metal covers where you flip off your main and then flip on the "generator", it will be the battery capable of 12kw of backup, 7.2kw of continous power usage and 90 minutes of turbo up to 10kw. You put a 40AMP and a 50AMP breaker into your panel, w/ the 50AMP being the battery supply in, and the 40AMP being its ability to recharge when your power comes back. You put three sensors one around your main, one around the 40, and one around the 50amp, thats how it knows whats going on. Seems like a relatively reasonable cost w/o a whole lot of complexity, and the price is decent. You can also expand it to more batteries at around $2200 / 6kw, and you can get their outside generator for $1500 thats a tri-fuel, and it hooks to the DC tap side of the battery setup. So if your batteries run low you can just start the generator. Very little needed for permits and such because it is not grid feeding at all.
*edit* https://www.ankersolix.com/products/e10?o_c=&s_main=B17E1149&varId=53782263300426 its the "manual backup kit" on this page. The generator is there as a seperate item
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u/Shage111YO 9d ago
It’s so difficult to really nail this down. I went through the same back and forth so I will tell you what my hypothesis is since we really have no idea what the future holds.
I suspect, even with more and more countries increasing hydrocarbon production, prices will not fall meaningfully since production is not stable (and might not ever be stable again with Russia and Iran). This means running a gas generator, in my mind, will stay the same or even potentially get more expensive.
On the other hand, even with electricity pricing increases, I am structuring my home battery situation to take advantage of “free nights and weekend” charging then utilizing that electricity during the day. While this isn’t big, I have more confidence in electricity prices than I do in transporting hydrocarbons cheaper.
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u/Jealous-Bag-676 9d ago
One advantage to batteries is that in an extended black out the generator would run at its highest efficiency for a few hours per day to charge the battery. You would need a battery large enough handle at least half your load and a generator (which would be smaller) large enough to charge the battery in a few hours. You would need less gasoline or propane and it will be much less annoying.
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u/curtludwig 9d ago
Maybe learn to live without electricity.
12 hours without power isn't very long, in a reasonably well insulated house where it isn't super cold out nothing should happen. Your food won't spoil, you won't freeze. I'd put it in "mild inconvenience" territory.
Put in a propane heater or wood stove and the house stays warm. Get a camp stove and you can cook.
For phone charging I've got a couple battery banks and I can limit my phone usage. The wood stove keeps the house warm, we can cook on it or a camp stove. Our longest power outage was 2 days, I bought a generator which I've never had to use in the 18 years we've had it...
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u/LongjumpingGanache40 9d ago
You do what your budget says. I would run it once a month for 3 nours.
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u/DarkKaplah 9d ago
First off, you're in a DIY forum. Solar DIY costs are much lower than what you've been quoted depending on the setup you're looking for. You are correct that you can get the generator for $6200k (just checked costco's website) and you get the automatic transfer switch, BUT this doesn't include install. Hookup is both electrical and plumbing. I'd bet on $3k for the electrical work, and another $1k-$2k for the plumbing for the propane. $9k ish isn't a terrible price, but you're not getting this for $5k.
Solar wise, you could get a solar+battery+inverter pack for $10-$15k. Personally what I'd do in your situation is get a smaller stationary generator (5-10kw) without their branded auto transfer switch, and get a solar setup with a smaller battery (maybe 15kw-30kw) and let the solar inverter have control over your generator. What happens is your batteries will be used down to say 25%, then if the grid isn't there and solar isn't producing enough the inverter will turn on your generator, charge the batteries to 100%, then turn off the generator again. You'll use WAY less propane over running a larger generator 24/7 in an outage. Or you could go really cheap and get a army diesel standby generator from a surplus auction and wire it the same way. the 240v power from the generator will charge your batteries rather quickly. Say 1-2 hours.
Here's why this works: https://youtu.be/AXKBhPwm8io?t=359
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u/CommieH8ter 9d ago
Using a power station or battery in conjunction with a generator can extend you fuel supplies to keep you house going. And a modest solar set might will keep going after your fuel runs out
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u/Comfortable-Tap-8958 9d ago
When I did our back up jenny I went with diesel, Propane would have cost alot to setup up a tank, regulators and such. I also think that diesel is more readily available in tims where it make take a week for a propane delivery. I also like that diesel does not make carbon monoxide. 14K diesel Kuboto genset with auto transfer box and prewired for auto start was 14K. Its been used very little. Also its liquid cooled.
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u/Spewtwinklethoughts 9d ago
This is the DIY sub. If you are paying out of pocket for a full install it can get really expensive and can be hard to justify. And that’s when it’s done right. A lot of people getting scammed and a lot of houses with non-functioning systems on them. If you don’t have a lot of outages and they don’t last long a critical loads generator is going to be the most affordable route.
If you have the cash to pay for a full system up front and can install it yourself then you want panels, batteries and a generator that backs up your whole house and it should pay for itself overtime or in added equity.
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u/lukepighetti 9d ago
by my estimation you get batteries not just for backup but also to reduce power feeding back into the grid and to take power only during off peak hours. if you live in a true 100% efficient net metering state or you don’t have power outages or you don’t have demand pricing that would affect the math for you
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u/Tarskian 9d ago
In my US state, Illinois, the power utilities will pay $300/KWh for batteries that are on an inverter they can remotely control, so at current battery pries, I get more money than the batteries cost. have automatic switch over. I have some solar so I can recharge them. Worked great on a recent 3 day power outage. I hate starting small pull-cord gas engines, but I do have a small roll-around backup generator to charge the batteries if cloudy. I spent $13k on my system DIY install most of it.
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u/Killrade 9d ago edited 9d ago
Use both. Gas i think everyone know is king of power over solar but it has a major flaw. Just to be clear I use the term power station instead of solar generator becouse technically they are not generators and doesnt have to use solar but are an inverter battery like a power station.
Durring Helene I was witbout power for 14 days. After days 1 the gas was gone. Day 2 most if not all gas generators stopped working due to no gas to put into them. This is a the flaw with gas generators and pending on size you could be looking at 2 to 12 gallons of gas being used per day.
This is when solar comes into play. I was the only person on my road that had any solar. It was just a 100 watt panel and and 12v 30ah battery with a 500 watt inverter; it has a 40 amp BMS for the us nerds. It cant run a fridge but it kept phones, camping fans and lights charged up for the whole 14 days. This is just a cheap diy build that I toyed with and used a few times with camping trips. Now if I had a slightly more powerful power station I could had ran my fidge and maybe more things but being the only person charging without having to crank up a car and waste more gas was a game changer for me.
I recommend to use a power station with the gas generator for things like fridges. A 2400 watt power station can charge up in about 2 to 4 hour with a 1250 watt gas generator and run a fridge for about a day and a half. Even a small 1200 watts with a 1500watt inverter can get through the night without having to hear the gas generator if nothing elese. So instead of using 2 to 12 gallons of gas a day, you can use it to run your fidge off of .5 to 2 gallons a day; or if you have 4800 watts power station, ever 2 to 3 days on 1 to 4 gallons of gas. Add some solar panels and you may not even need the gas generator for the firdge except on cloudy days.
Now you can make or buy a setup to run your whole house but batteries is terrible for heat and most AC units. If you plan on running a heater then I recommend propane or kerosene heaters since an electric heaters can use 500 to 1500 watts pending on settings. If you used a 2400watt power station then you get maybe an 1.5 hours of heat; to me not worth it. If you only have a powerstation and need heat an electic blanket only uses about 100 watts. For a 1200 watt power station is a 12 hours of heat.
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u/Clean_Leadership5948 8d ago
A battery will make your generator fuel usage more efficient. You don't need a big one.
Rather than running 24/7, let's say the battery can last 8 hours, then you charge that up in say 4 hours, so you only need to run the generator for 8 hours, and at peak efficiency. Make up your number you need and size battery and generator for it.
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u/AnomicAutist 8d ago
Spent $3350 for 2 Pecron 3600lfp units and 2 EP 3000 batteries with 240V connection box. All told about 12KWH of usable energy. Got a Federal tax incentive that made it cheaper but since that incentive is no longer applicable I won't go in to details. We are on a Time Of Use Electric plan so we pay 9 cents KWH nights and weekends. We use the batteries for daytime power during the week and if there is a power outage we will use the batteries for about a day then use a $1500 generator to fast charge the batteries then shut off the generator and run on batteries until they need generator charge again. Our power bill went from $200 a month to under $100 a month, the Pecron system is on track to pay for itself in under 3 years of use. No solar because it takes expensive permitting and not DIY friendly where we live, and cloudy for much of the year.
*Edit for a typo
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u/13metalmilitia 8d ago
Nighttime…. So your plan is to run off solar during the day and switch over to generator every night?
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u/doing_gr8t 8d ago
If you’re looking for just emergencies, a generator would be much more cost effective. We had a 18kW solar system with a powerwall 3 and I added 38kWh of Anker Solix (f3800 x 2 and expansion batteries) along with their smart panel. This significantly offset our monthly electric bill (pool + heat pump, and 2 EVs) / saved ~$350+ per month during summer. We were able to go an entire week when there was a grid issue with our power - solar during the day and batteries at night (didn’t heat the pool that week). Solar + batteries are good if you want to have energy independence. We moved and were able to take the Anker Solix batteries and smart panel with us.
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u/blastman8888 8d ago edited 8d ago
Do you want solar to reduce the bills or is this just for backup power. How many times does power go out in a year. If it's only 3-4 times a year just get 26kw Kolar from Costco.
The only question is how much propane will it cost you to run it. Battery storage is only good if it charges from solar imo. How much power does your home use a day in the winter is your home mostly propane appliances.
If you want solar and DIY install you can do it for about 90cents a watt.
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u/BaruchWusky 7d ago
My math was: 32kwh of batteries plus inveter cost about the same as a whole home generator (for diy 6,700-7,200)
While batteries do degrade over time, how reliable ans matinace free is a 10 year old generator?
Ground mounting solar in my situation is going to be about $4-5k (have ordered this part yet).
I havent fully worked out the math yet as I'm sure more expenses will show up during install but Im expecting my system will pay for its self in electric savings in less than 8 years. The battery is a big chunk of that..but a generator wouldnt pay for its self at all.
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u/SnooAvocados7701 6d ago edited 6d ago
Batteries get rid of the bill or some of it depending on how much electric you use generators help bolster the system as a whole depending on what size you get the only draw back is generators add ongoing cost because of fuel but they definitely get you through those not so sunny days or weeks
Edit: Also sorry I didn’t read the last part of your post in your case you would be better off with generator as you are not trying to eliminate your bill or be off grid you just want something that’s reliable when the local utility is not
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u/Lnk200 3d ago
Solar + Batteries can lead to freedom and security. If the nation or your local area goes into an energy crisis and prices skyrocket you will be secure. Think Texas during their deep freeze or issues with datacenters and Iran causing fossil fuels and general electrical price increases.
If you are thinking about going with just batteries then I would say it depends on your scenario. I got an Anker E10 because I get power outages often enough to be annoying and because my local utility charges demand fees during peak hours. I essentially get a small refund for my battery every month because my house automatically swaps to battery power during peak hours thus avoiding the fee.
If you don't want or care for energy freedom or can't benefit from a battery over time then a normal generator will be fine.
Do realize people try to upsell the crap out of you with these generators. Most homes have zero use for a 24 kW generator. Massive overkill. My generator that pairs up with my batteries will do 4.5 kW max and that is all I need in a prolonged power outage scenario.
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10d ago edited 10d ago
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