Help! Need to run a heater on solar/battery

[Brennana]

Hi.
We have a small office (wooden cabin). We use it every day. To heat the office 8 hours per day we use two 1 kw heaters. I'd like to try and run these heaters on solar panels and batteries. I'm facing south.

I would be very greatful if someone could point me in the right direction. In terms of the kit I would need to achieve the deliveribles.

Regards
Aidan

 

[Supervstech]

You need to measure the kWh usage over the day, and double it for battery size.
I’m guessing USA market?
1.5kW heaters?
That would be 6kWh first two hours heating constantly, then likely 50% the rest of the 6hrs left, puts you approximately 15kWh usage, so, 30kWh battery, then you need an inverter capable of running two heaters, so a good high efficiency inverter pulling 3kW is cheap… bumping to 6kW to handle other things you may want to use off solar…

 

[rmaddy]

All of the following is rough estimates. Adjust the numbers as needed to meet your reality.

2 1kW heaters is of course 2kW. At 8 hours per day that is 2kW * 8h/day = 16kWh/day of power assuming both heaters ran at the full 1000W for the full 8 hours. Maybe the heaters only run 50% of the time so you might only need 8kWh/day.

Let's say you choose LiFePO₄ batteries and you can use 90% of the battery power each day. Then you need 16kWh / 90% = 17.78kWh of battery. That would be 350Ah of 48V LiFePO₄ batteries.

If you choose lead acid types then you need 32kWh of battery since you can only discharge to 50%.

Those assume you can fully recharge the batteries each day. If you want to account for no solar for a few days due to bad weather then you need to multiply that times the number of days you want to support.

You need enough solar to fully recharge the batteries each day. In the winter you might only get an hour, maybe two of good solar each day, depending on where you live.

16kWh / 1.5h of sun is about 11kW of solar. And that assumes you can get 100% of the rated solar. In the winter that's not likely. Depending on how you can mount the panels you might need 20kW (or more) of solar panels to get the 11kW.

And none of this accounts for the power used to run the inverter that you need.

Running those two heaters will require an absurd amount of money in battery and solar. You might want to look into a generator instead.

 

[Bud Martin]

Not practical.
Are you on grid right now? How much are you paying per KW-Hr?