Hi! Probably the most frequently asked question we get here is, “How much solar does it take to power my 2,000 sqft home?” My answer is always the same. “I don’t know. How much power do you use?” I’m not trying to be flip, I honestly don’t know. The power usage for different homes are going to be so wildly different, there is no way of knowing how much power someone uses based on their square footage. Is the house located in the north with bad insulation and electric baseboard heaters? Or is it a house with a tight building envelope and gas heat? Is it located in the south with the highest loads being air conditioning run 24/7, or is it in a mild environment with a couple of fans occasionally? Are you heating your water with an electric water heater, or an oil furnace? Do you have family members who find it challenging to turn off a light when they leave the room (you know who you are)? Are you lighting with incandescent or LED light bulbs? The best way to determine how many solar panels you need is to look at your electric bill and see how many kWh a month you buy. You can then go to our grid-tied calculator to see how much solar would be needed to offset a percentage of your bill. Here’s an example of my electric bill. It shows 13 months of usage, so I can compare the latest month with the previous year. It is amazing what you can learn by studying your electric bill. By comparing the usage in different months, I can see my biggest use is in the summer, with the air conditioner running all day because of the home office. You can see that my usage dropped significantly from August 2018 to August 2019, as well as from July to August in 2019.
We went away every weekend in August 2019, and turned the AC off while we were gone, saving us $85 from the previous year. But unfortunately, we went away for a week that July and forgot to turn down the AC, so it stayed on high, cooling an empty house all week. You can see that’s the highest usage in 13 months and was completely preventable. That mistake cost me about $160. In November we switched the mini-split from AC mode to heating mode to delay turning on our oil heat, bringing our electric usage back up. It cost an extra $135 to heat the house with electricity that month, but saved us at least that much on our oil bill. By December it was too cold for the heat pump to work, so we turned it off and turned on the oil, dropping our electric use. So even in the same house, with the same people, behaviour changes the electrical use dramatically, thus changing the answer to the original question, “how much solar do I need to power my house?” I recommend you look at your monthly usage and analyse it, what was your big energy user each month, and could a change in behaviour reduce it? Once you understand your electric use, then you can start to figure out how much solar you need. Our average use is about 1,500kWh a month. I used that number in our on-grid calculator and decided to see what it would take to make all of our power with solar, netting us down to 0. That would require around a 13,000 Watt solar system for my area, around 50 solar panels. This chart shows my last 30 months of electric use, and the estimated output of a 13kW solar system on my house for that time.
With Net Metering, I can use any power I generate during the day and sell the extra to the grid. Then at night, when my system isn’t generating any power, I can buy it back from the grid, spinning the meter back and forth. Any additional power I need gets bought from the grid, same as usual. Likewise, with months that I make more power than I use, like in the spring, I can bank the credits to use them in the summer and winter when I don’t make as much as I use. Today’s average costs would be around $26,000 to buy the equipment to install it yourself, or about $52,000 to have one professionally installed (depending on equipment and location). A combination of federal and local incentives could cut the cost by ⅓ to ½ in the US, depending on your location. This system could pay for itself in about 8 years for me. After that, and for the next couple of decades that my system keeps humming along, the $3000 a year I was paying to the electric company stays in my pocket. Plus with rate increases, that savings is bound to grow over the years. But a nice thing about net metering, and staying connected to the grid, is I don’t have to make all of my power like if I was off-grid. I can instead decide to make half my power, or less, and buy the rest from the grid, resulting in a lower monthly electric bill. You can see from this graph that charts both my monthly use and my projected monthly solar generation with a 6.5kW solar system, that for a couple of months
I actually would make all of the power that I use, but on average, I would make half of the power I needed, cutting my power bill in half. That still gives me a significant monthly savings. Solar isn’t the silver bullet for reducing my electric bills. We’re also working on further reducing our power use. We recently replaced all of the shop lights in the basement with LED tubes. This brought that power use from 2500W down to about 250W! And the light quality is better now than with the old lights. We’ve replaced all of our incandescent light bulbs throughout the house with LED as well. We’re also trying to get smarter with the programming of the air conditioning, cutting down on our biggest power user. So you can see why the most common question we get asked here is also the most complicated and personal question to answer. Grab your electric bill, go to calculator, and find the answers for your home. I hope this was helpful. If so, give us a share.