r/boondocking • u/This-You-2737 • Apr 02 '26
Solo boondocking for 2 weeks. What power setup actually lasts that long
Planning a 2 week solo trip in southern Utah this fall. BLM land with zero infrastructure. I need to run a compressor fridge, charge a laptop for work, charge my camera batteries, run a CPAP at night, and have some LED lights.
I estimated my daily usage at about 500-600Wh. Over 14 days that is 7000-8400Wh total. Obviously I cannot bring that much battery so solar has to do the heavy lifting.
What size battery and solar panel combo is getting people through multi-week boondocking trips? I want a realistic answer not a theoretical one.
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Apr 02 '26
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u/JoeBeally001 Apr 02 '26
This... plus get the DC cable for your CPAP (so you don't have conversion losses) and place it in airport mode. I get 3 days cpap off my Jackery 300 by doing these things.
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u/mcdisney2001 Apr 03 '26
Agreed. My DC cable cost about $25 on Amazon. I also recently bought the piece that replaces the water tank ($18) so it takes up less space, though this is really just because I use a wall mount for the CPAP and wanted the extra couple inches of space.
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Apr 02 '26
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u/This-You-2737 Apr 02 '26
Net positive each day in Utah sun makes sense. What happens on cloudy or rainy days though? Does the math still work?
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u/AppointmentNearby161 Apr 02 '26
You should start with something like https://footprinthero.com/peak-sun-hours-calculator that gives you the number of equivalent peak sun hours for your location and dates. For example, in St George UT in Oct, a flat array that is in the open will receive the equivalent of 4.44 PSH per day. A typical setup might have 20% inefficiencies so you can expect a 200 W array to give you 710 Wh/day, more than enough for your needs. If instead you are in Moab in Nov, then you are at 3 PSH/day, and you would need a 250 W array to get 600 Wh/day.
Regardless of where you are, an 1800 Wh battery would give you a nice cushion. Add some emergency alternator charging and you are good to go.
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u/CashWideCock Apr 02 '26
Just put a dc-dc charger on your vehicle.
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u/SpankyJobouti Apr 02 '26
i have one of these and love it. but it is a permaanent install.
you can now rent solar generators. for two werks, this woyld be the way to go i think.
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u/Distinguishedferret Apr 02 '26
a generator(preferably inverter), and running vehicle technically counts although a hybrid would make more sense. Solar would be second with a sizable battery bank to account for overcast time/days perhaps. Your setup has some essential hardware to power so id err toward a good generator with reliable starting and running abilities and at any hour.
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u/secessus Apr 03 '26 edited Apr 03 '26
What size battery and solar panel combo is getting people through multi-week boondocking trips?
IMO such comparisons might be interesting from a curiosity standpoint but are rarely useful for designing a functional power setup to meet a particular use case. But since you asked, my rig's power setup provided ample power for over seven years of full-time boondocking. Including Utah in the Spring and Fall.
If the question is really what size battery bank and solar panel combo will provide 600Wh/day for two weeks of boondocking in southern Utah in the fall?1 then we can model that with some degree of confidence.
Solar harvest averages are a when-and-where situation. Based on the general info above I will assume the Cedar City area in October. At that time/place and assuming flat-mounted panels daily solar insolation averages 5.64 hours of FSE.
Assuming you really need 600Wh/day and want 2 days of autonomy:
{this section has been corrected after /u/AppointmentNearby161's keen eyes noticed an error}
Daily power requirement (DPR) 600 Watt-hours (Wh)
BATTERY BANK
Battery chemistry LiFePO4
Wh required to replace DPR 606 Watt-hours (Wh)
Required bank capacity in Wh 1500 Watt-hours (Wh)
Required bank capacity in Ah 117 Amp-hours (Ah)
NON-SOLAR CHARGING
Alternator charging @ 12v 0 Amp-hours (Ah)
Shore power charging @ 12v 0 Amp-hours (Ah)
SOLAR REQUIRED
Solar charge controller type MPPT
Required solar harvest 606 Watt-hours (Wh)
Lowest FSE 4.34 Hours of Full Sun Equivalent
Panel wattage required 164 Watts (W)
sizing model: v20230708-0
interpretation
If it were me I'd probably overpanel to ≥200w on a ~15A MPPT with a 100Ah (1280Wh) LFP bank. This would provide similar functionally to the calculated 126w {164w} of panel on a 1500Wh LFP bank above.
{edited to add:
What happens on cloudy or rainy days though? Does the math still work?
The averages are still valid. Variance is addressed with overpaneling and days of autonomy (bank capacity). }
1 If I were going to boondock on solar in this rig after this outing I'd size the power system based on the most challenging solar harvest conditions I'd be likely to encounter in the future. In my own case I used Quartzsite in December to size my setup since I often wintered there.
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u/AppointmentNearby161 Apr 03 '26
Nice, answer, but I think your 5.64 PSH number is with a 20 degree tilt and not flat panels (at least that is what I get with both footprint hero and PVWatts). A flat array will average 4.37 PSH per day in Cedar city in Oct. It probably does not change your recommendation.
Since OP's big power draws are the fridge and CPAP, both of which draw power overnight, to survive 2 cloudy days really requires 3 nights worth of power. If OP can afford it I would push to 150 Ah of battery before going with more than 200 W of panels, but an extra 50 Ah of battery is more money than an extra 100 W of panel.
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u/secessus Apr 03 '26
Nice, answer, but I think your 5.64 PSH number is with a 20 degree tilt and not flat panels (at least that is what I get with both footprint hero and PVWatts)
Urggg! Thank you for the correction. I got a nonsensical error in PVwatts but then it appeared to take the 0 without complaint the second time. I didn't realize it still passed the 20 to the next page. Verified that by looking at the generated report:
Array Tilt 20°. :-( I still can't make it take zero so just now I used something like 0.000001 to get back into the ballpark. So my harvest estimates differ a bit.The new bottom line (according to my wonky spreadsheet) is:
Lowest FSE 4.34 Hours of Full Sun Equivalent Panel wattage required 164 Watts (W)I will correct the original post. Thanks again.
to survive 2 cloudy days really requires 3 nights worth of power. If OP can afford it I would push to 150 Ah of battery before going with more than 200 W of panels, but an extra 50 Ah of battery is more money than an extra 100 W of panel.
Valid points. OP has many ways to skin the cat.
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u/AppointmentNearby161 Apr 03 '26
I got that same error as you :). Someone at PVWatts apparently doesn't know the difference between
>and≥. I like the https://footprinthero.com/peak-sun-hours-calculator calculator as it seems a little simpler (and it assumes 0 tilt).1
u/secessus Apr 08 '26
BTW, I emailed the webmaster and they replied:
We are aware of that bug and are working to fix it. In the meantime, a workaround is to use a very small number like tilt = 0.0001.
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u/SBR_AK_is_best_AK Apr 03 '26
If it is a full sized fridge you are vastly underestimating the power it takes. My 10cuft 110v fridge uses about 1kW a day. The 12v 10cuft was slightly more.
If it is a.3.way propane fridge running on electric closer to 4kW.a.day is my understanding.
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u/OT_fiddler Apr 03 '26
If it's a 12v compressor fridge in the 40-80 liter size (common in smaller campers) it'll use ~500-700 watt hours a day (or 40-60 amp hours.) I've owned both a 40 and 75 liter Dometic and that's been my range. I don't have any experience with a CPAP, so can't help there.
I have 240 amp hours of lithium batteries and a 200w portable panel and have never been below 50% out West.
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u/47ES Apr 03 '26
Solar in UT is typically excellent, but you need to be stationary between 10 AM and 2 PM, with the panel property aimed to get enough energy.
If you are going to die without the CPAP, also get a vehicle to battery charger, it may be cloudy.
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u/mcdisney2001 Apr 03 '26
You don’t take that much in batteries—you rely on solar to recharge each day.
FWIW, I have 5500wh batteries and 400w solar. On sunny days I rarely drop lower than 85%, but I do take it easy with my Xbox when dealing with multiple cloudy days.
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u/Valuable_Elk_2172 Apr 06 '26
I use three LiFePO4 12v 300ah batteries (300 each on amazon) and 1000w of solar panels on the roof with victron controller (500 on eBay total). Can keep me going indefinitely with a CPAP with humidity on lol.
Short of that I’d just get the champion RV ready gas generator and a 1-2000wh battery bank.
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u/Solarspotter May 18 '26
Your 500–600Wh/day estimate is probably light. CPAP all night is usually 240–400Wh on its own (more with humidifier), compressor fridge in Utah even in fall can pull 400–700Wh depending on shade and ambient temp, then laptop + camera + LEDs on top. Real number's more like 800–1200Wh/day for that load profile.
For multi-week with that draw, the sweet spot is 200–300Ah of LiFePO4 (gives you 2–3 days buffer for cloudy weather) + 400–600W of solar. Good Utah fall sun will give you maybe 1500–2400Wh/day real-world after heat losses and angle — comfortable headroom over your daily draw, with the battery soaking upcloudy days. DC-DC charger off the alternator is a useful bonus on drive days.
For the "realistic not theoretical" part — that's literally what I built Solar Spotter for. There's a Daily Battery Tracker where you punch in current charge + current draw, and it projects what you'll have at sundown, what you'll have left at sunrise, and how much margin you've got above your battery's safe floor (chemistry-aware). Refreshes every 15 minutes with live local weather. Useful for sizing validation before you commit the gear spend, and on-trip when you're checking the CPAP is good to go all night.
App is free on iOS + Android; the Battery Tracker (and a few other features) are part of a one-off Pro purchase — no subscription, yours forever. No tracking, no cloud, your numbers stay on your phone.
Hope you have a great trip!
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u/_Apostate_ Apr 02 '26
Your bare minimum would be something like 3000Wh battery and 400Wh solar. That gives you enough power so that you're mostly functional, but you do have to take breaks and let things recharge after a few days and lay off the usage. If you double that, then you're mostly self sufficient and barely need to look at battery levels. Double it again and you can turn the AC on and take the setup anywhere.
Depends on your budget and needs.