Solar Panels Watts
how do I convert the out put of solar panels in watts to kilowatts per month.?
I am looking at a set of solar panels that produces about 400 watts of electricity and plan to use them on a grid tie system. My house uses about 700kwh per month.
Multiply 400 watts times hours per month time efficiency. Divide by 1000 to make kW.
Say 400W * 200hr/mo * 90% /1000
= 72kW-hr per month.
The efficiency above is for misalignment to the sun. As the sun moves during the day, it’s rarely perfectly oriented. Also, some panels often don’t put out rated current. If they get dirty, less power.
BTW, two big issues are that solar cells make direct current (DC), often at 12V or 24V nominal, and you may need electricity when the sun doesn’t shine (like overcast winter days or at night). Thus, you need storage batteries. These loose another 10 to 20% of the power. Since houses use 120V AC, you need an inverter, which loses another 10 to 20%. Driving 240V loads, like dryers, ranges, air conditioners pretty much out of the question.
Solar generally not economical for most of us; if you’re Ed Beggley, cost is no problem, go for the solar!
7.5 watt CIGS solar panel review
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