One of the first question people usually ask when are researching solar power for residential use is how many solar panels do you need?
Before we get into calculating how many solar panels you will need to power your household, we need to define some terminology. The most basic measurement of electrical power is the watt. Since a watt is such a small measure, most appliances are measured in kilowatts, or 1000 watts. Utilities use kilowatt hours to measure your power usage. For example, one kilowatt hour is equivalent to leaving ten 100 watt lightbulbs running for 1 hour. (10bulbs x 100w x 1hr = 1000 watts per hour or 1kwh)
The next largest measure is the volt. A volt is how much force of current the electricity carries through an electrical source. Plug outlets that produce more voltage carry more electricity. You may have seen 120V outlets and 220V outlets. Another unit you may come across is an “amp.” An amp measures the strength of electrical power in a wire or device.
The first thing you’ll want to do when you are calculating your electricity usage is to pull up your old electricity bills. Past electricity bills are the best predictor of future usage. Average American households use around 1000 to 1200 kWh per month.
Look for the trends in electricity usage. Has the usage gone up over time? Most solar experts will tell you to buy more solar panels, because it is better to have too much than not enough. The most common solar panels measure 4′ 5 by 2′ 2 and rated 120 Watts at peak power. Using this calculation, one panel will produce 1.04 kWh per day at peak power. For the average home, assuming they consume 100kWh per month, to be completely powered off 120w solar panels, they need around 32 panels.