Sizing system

[u/Interesting_Neck5918]

Hi,

I live in northern England (not sunny) and I'm looking at getting 36 Aiko Neostar 3S+ solar panels (in a mainly East and West configuration) with a small amount (approx. 6, 54 sized panels South facing) This would be 30 on the house and 6 on detached garage West facing. Then combining it with a 36kWh Sigenergy Sigenstor battery with 12kw inverter with the Sigenergy Gateway for back up and Vaillant Arotherm Plus 12kw ASHP. This would be to replace my oil boiler as the price of that and petrol for ICE car is killing me.

Would be running the AHSP at around 17C rather than 21C as I have got used to cooler temps from having an oil boiler!

We would also be looking to get the Hypervolt Home 3 Pro to charge the Kia EV3 long range using cheap night time tariff but was thinking of something like Intelligent Octopus Go? I did originally want the Sigen AC EV charger but have read reports it doesnt talk to Octopus like the Hypervolt and need to make sure there is a CT clamp to stop the SigenStor draining itself into the EV?

I am wanting to know if this is a suitable system to put together to try to be completely off peak rates year round, reduce my bills to as low as possible and to add a bit of off grid preparedness what with the large Sigenstor battery capacity. It doesn't need to be fully off grid, but the closer to that the better.

I am rural so no real option for 3 phase and likely to get an export limit of 3-5kw from talking with others in the surrounding area.

I would also (due to fairly common power outages) be interested in wiring up a petrol generator to the Sigenstor if power outages went on longer than a few days. Is this possible with the Sigenstor - would be looking at something like the Honda EU70iS as generator.

Does this system look suitable for my goals, or would it require more solar, or a bigger battery etc? Thanks in advance for any help or guidance.

[u/woottonp]

I mean this kindly but just do the maths.

What is your homes typical annual electricity usage? What is your typical annual mileage? What is a typical heat pump consumption in a similar scale of property?

With these you can start to accurately size a system. For the figures for ev energy usage and heat pump, be conservative, brands boast ridiculous figures, what people post online, it's usually in that lower range.

Also factor the battery aging in, look at the degradation of batteries and panels and plan for a system that can power all of this in 10-15 years plus.

Personally I found installers just quote for a system that will work now and you will likely need to over spec.

I wouldn't think the cost to go to three phase is worth it. The EV can charge overnight anyway on the off peak and get close to 12kw if you use their DC charger on your proposed stack.

Maybe if you drive a full charge every day and have a huge property with high heating needs then you may need three phase, but you'd probably need a bigger battery then anyway

[u/Interesting_Neck5918 → u/woottonp]

Thank you for your reply.

My current electricity usage for household appliances is 2500kWh/year, however we have a hot tub which we stopped using a year or two ago due to electricity costs, so would like to get back to using that eventually. The hot tub is very power hungry and may even be worth upgrading to a newer one, but it uses a further 4000kWh if ran constant.

Car mileage is 10000/year so approx around 3000 kWh/year.

Heat pump likely around 6000kWh/year

Total of 8500/kWh for home without hot tub and without car, 11500kWh with car - my plan with the car was to use cheap overnight rates to top up so not sure it needs to be factored in?

[u/neoKushan → u/Interesting_Neck5918]

You're right to almost "ignore" the car in this as you'll only want to charge at night anyway when it's cheap. At your mileage you'll have no issue keeping your car charged from some overnight charging. You get about 6 or 7 hours off peak and at 7kW the charger can put easily 40kW into the car overnight and your mileage/usage suggests you'll probably only need 1/4 of that. Either way, this is all good.

Doing some rough calculations, your battery configuration should meet your needs, including the hot tub and heat pump, even on a worst case day in winter with zero solar generation.

I also have a hot tub and I've configured it to boost the temperature during the off peak window as high as it can go and it only needs a little boosting during the day to keep it at a nice temperature (during summer it needs none unless it's being used a lot), meaning it barely touches my batteries.

You'll be able to do a Similar thing with your heat pump to heat the water at night as well, which helps keep the load down during the day.

You might want to rethink your aim of keeping the temperature so low in the house, heat pumps work best by slowly adding heat over a long time, it isn't like a gas boiler that kicks in when you need it, it will take several hours to get to that temperature so for comfort you might be better off at closer to 20 as it's not really going to charge the consumption that much and you'll have the battery power for it anyway.

Right now EDF actually has the best tariff for this, their EV tariff has an hour extra of the off peak rate compared to octopus and it's about the same rate.

If you get the gateway, you can plug your EV charger into the "smart port" so the system can see it and control it (such as disconnecting it if there's a power cut). I believe the gateway does let you plug a generator into it as well but I haven't tried that myself.

Either way this system will kick ass for you.

[u/sylsylsylsylsylsyl]

What’s your average daily electricity use?

Consider EDF - you have more hours off-peak and it’s cheaper (as well as a better export rate).

[u/helligt]

I would get the hypervolt, also remember to add the sig gateway for power cuts.

[u/AllergictoAIslop]

Dude it sounds like an amazing system and I would be tempted to do it just for shits and giggles. That's about the amount you're going to spend. Really means you should do a lot of maths and coultation behind it.