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Solar power adoption is growing globally, with solar panels evolving significantly over the years. But many homeowners remain cautious about shifting to solar as their primary power source, and practical questions, like how many panels would be required to run household appliances, are common.
For Americans quietly installing solar to fight skyrocketing energy bills, a single residential solar panel would likely suffice to power a typical modern washer, given the right circumstances. A number of factors will ultimately influence the final determination, including how often you’re running your washer (a major factor in how much power it consumes), as well as where your solar system is located. Location determines a great deal about solar power generation, based on variables like local sunlight, shading, and roof orientation.
It’s important to differentiate a panel’s rated wattage from its actual output. While a panel may be listed at 400 watts, it only produces electricity when the sun is shining, and real-world output changes by season, tilt, orientation, temperature, shading, and system losses. That said, it’s still possible to do some ballpark math and estimate out how much power you’d need to drive an average washer.
A single panel may not suffice in real-world conditions
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Conveniently, the federally required EnergyGuide label on appliances indicates a washer’s estimated annual electricity use in kilowatt-hours (kWh). These numbers are collated in the Energy Star product database, so we can get a snapshot of what some real-life averages are. 105 kWh is around the mid-to-high end of usage, so we’ll use that as the starting point for our calculations.
A 105 kWh washer uses around 0.29 kWh every day. To figure out how many kWh a 400W panel produces in real-world conditions, let’s turn to data on the Environmental Protection Agency site from the National Renewable Energy Laboratory, which showed that a 1,017.14-kW solar system located in Kansas City produces 1,455,726 kWh annually. That works out to about 1,431 kWh per installed kW per year at that location and under those conditions. Using that as an example, a 400W panel would crank out somewhere around 572 kWh annually.
Under those circumstances, our 105 kWh washer would only need 18% of that panel’s annual generation, meaning a single panel would be more than enough to power it. However, there are a number of other factors to consider. Assuming the panel wasn’t connected to the grid and you wanted to run the washer when the sun wasn’t shining or on a stormy day, you’d need to include a battery and inverter in your system. Those calculations also don’t include the energy cost of a hot-water heater or any other appliances, like a dryer, that may be involved in every load of laundry. If you’re designing a solar system, you should take a more holistic approach (and also avoid these other common mistakes when considering solar panels).