How Many Solar Panels Do I Need? 2025 Calculator | SolarTech
How many solar panels do I need? Use our 2025 calculator to size your system by home size, kWh usage, and location. Get panel count, roof space, and kW—free from SolarTech.
The goal for any solar project should be 100% electricity offset and maximum savings — not necessarily to cram as many panels on a roof as possible. So, the number of panels you need to power a house varies based on three main factors: In this article, we'll show you how to manually calculate how many panels you'll need to power your home.
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.
Solar panel power ratings range from 250W to 450W. Based on solar.com sales data, 400W is the most popular power rating and provides a great balance of output and Price Per Watt (PPW). If you have limited roof space, you may consider a higher power rating to use fewer panels. If you want to spend less per panel, you may consider a lower wattage.
You can calculate how many solar panels you need by dividing your yearly electricity usage by your area's production ratio and then dividing that number by the power output of your solar panels. To put it simply: Number of panels = annual electricity usage / production ratio / panel wattage
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