How Many Solar Panels Does It Take to Charge Your Battery?
A battery only stores what your solar panels make after the house takes its share. Pick a battery and see the true scope, panel by panel.
Already have solar? Use your bill from before the panels went in.
9
panels just to refill the battery from empty
15
panels to refill it and run the house while the sun is up
13
panels in a system sized only to your bill
To refill it completely from empty, plan on about 2 more panels than your bill alone calls for. 15 panels to refill the 15 kilowatt-hour battery and run the house on an average day; a bill-sized system has 13 panels and refills 85%.
To refill it completely from empty, plan on about 2 more panels than your bill alone calls for
On an average day, 13 Q Cells Q.TRON 430 W panels run your daytime loads and refill about 85% of a 15 kWh battery. Refilling it completely takes about 15 panels (6.45 kW), roof space permitting. On a normal day the house only draws about 14 kWh from it overnight, so a full refill matters most after an outage.
Estimate only. Roof space, shading, tilt and your actual usage change the count; your proposal is the design. Not a backup-duration or savings guarantee.
How we count
- Each solar panel makes 1.77 kWh on an average day: its rating × 1,500 kWh per kW per year (our conservative Inland Empire figure) ÷ 365.
- Refilling takes about 5% more energy than the battery stores, for charging losses.
- Your bill converts to about 24 kWh a day; we assume 40% of it (10 kWh) happens while the panels are producing, so those panels can't charge the battery.
- Every count assumes the battery starts empty, as after an outage. On a normal day it only replaces what the house used overnight, about 14 kWh.
- The bill-sized count is the same sizing our system configurator uses, which tops out at 60 panels.
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