How Much Solar Power Does Your Home Need To Go Completely Off-Grid?

Solar power is becoming increasingly ubiquitous, though it remains the kind of technology that new consumers have a bevy of questions about. Alongside other things you'll need to know when installing solar, one of the most important considerations is how much electricity you'll need to generate for your home to completely stop relying on the grid for power. The answer, of course, depends on a number of variables, including things like your energy consumption, and the type and efficiency of your solar panels. Your home's location and the amount of sunlight it receives are also factors, which can vary dramatically based on season).

That said, it's possible to find some estimates based on averages for the typical American household, and also to directly measure your home's power usage, as well as the likely "energy income" your panels will generate. Another important element of your setup is battery storage, to ensure that you'll have enough power in reserve to cover your needs on overcast days or during shortages and usage spikes. To shave your power bill even further, you could also consider installing some of these extra solar-powered gadgets.

According to the U.S. Energy Information Administration (EIA), the average U.S. household uses roughly 10,500 kilowatt-hours (kWh) of electricity every year, which breaks down to 875 kWh a month or 28.8 kWh a day. You can find your personal energy usage by checking your power bill (look for a section labeled "Usage," "Electricity Consumption," or "kWh" on your monthly statement), or by checking your meter (note the number today, wait 30 days, and subtract your starting reading from the new reading to find your total monthly usage).

Next, you'll need to figure out how much energy an individual solar panel will generate. A simple way to estimate it is to multiply the panel wattage by the average peak sun hours and multiply that by the system efficiency. For example, a 400W panel in a location with 4.5 peak sun hours and 80% efficiency would result in the following equation: 400 × 4.5 × 0.8 = 1,440 Wh. That equates to 1.44 kWh per day. To discover how many peak sun hours your location receives, check a peak sun hours calculator. You can also make use of a solar calculator.

Finally, divide the energy usage of your household by the output of an individual panel to determine the number of panels you'll likely need to supply your home. Going slightly over will always be preferable to being under your required output and finding yourself regularly coming up short and having to rely on the grid to bridge the gap, hence the 20% rule when installing solar.