How Many Solar Panels Do I Need?
Most residential panels today are between 350 and 450 watts. Under ideal conditions, a 400W panel might produce about 1.6 kWh per day (depending on sunlight).
The size of a house plays a major role in knowing how many kilowatts of solar power your panels will consume. A 1,500-square-foot home would use an estimate of 630 kWh, whereas a 3,000-square-foot house would consume 1,200 kWh per month, twice as much. The national average for solar panels costs around $16,000.
As we calculated earlier, the California household needs a 7.2 kW system to cover its electricity needs. A comparable household in Massachusetts needs a 9.9 kW system. So, in less sunny areas like Massachusetts, you might consider choosing highly efficient solar panels to maximize your energy output per square foot.
12,000 / 1.6 / 0.4 = 18.75 panels (round up to 19) While energy usage varies significantly between households, home size provides a useful starting point for estimation: Smaller homes typically use 6,000-9,000 kWh annually.
Assume you have a 400W panel, but due to inefficiencies the actual output is 25% lower than 400W, which equals 300W effective. With 4 hours of effective sunlight, one panel produces: 300W × 4 hours = 1,200 Wh or 1.2 kWh per day. If your house uses 30 kWh per day, then you need: 30 kWh ÷ 1.2 kWh per panel ≈ 25 panels.
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