PV Gap

Tanya Said:

How much solar power would I need to run an 1,800 square foot house?

We Answered:

Square foot has little to do with it.

Electric heat, lots of AC, electric stove etc are a lot more important. What you need to do is look at old electric bills. Look at summer and winter and get the number of kW-hours for each month to get an average number, plus highs and lows.

Also important is location. Deep south with lots of sun versus northern maine with little sun. Do you have a roof that faces south with no shade at any time of the day?

First decision you need to make is grid tie or lots of batteries. Grid tie lets you sell excess power to the power company when you have a lot of sun, and buy it from then when there is no sun. The alternate is a huge bank of expensive batteries to store energy. And it can come to hundreds of batteries at hundreds of dollars each.

If you go with batteries, you have to pick a number of hours that you want to get power from the batteries when the sun is out. You can have many days with no sun, and that means a lot of batteries. If you decide to supply power for 5 sunless days as opposed to 1, then you need 5x the number of batteries.

Get a number of kW of power you need, and multiply that by a factor, perhaps 3, so you have excess to charge the batteries or sell to the power company. Then you have a start on sizing the panels themselves.

Get all those numbers together, then I can go over the numbers with you. Be warned, even with no batteries, this is more than US$30,000. Perhaps a lot more.

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