How many solar panels do I need?

The honest answer depends on three things: how much electricity you use, how much sun your location gets, and the wattage of the panels. The simple formula is panels = annual kWh ÷ annual kWh per panel. In an average US location a single 400-watt panel makes roughly 549 kWh per year (0.4 kW × 4.7 peak sun hours × 365 days × real-world losses). Divide your yearly usage by that and you have a solid first estimate.

Worked example: an average US home

The typical US household uses about 10,500 kWh a year. Dividing by 549 kWh per panel gives roughly 19 panels — which is about a 7.7 kW system once you account for how the panels are sized to local sun. That array produces about 10,567 kWh a year and costs around $22,638 before incentives. Use the tables below to find the number closer to your own home, then confirm it against your real usage.

Solar panels needed by home size

Modeled from a US-average electricity intensity (~5 kWh per sq ft per year), 4.7 peak sun hours per day, and 400-watt panels. Floor area is only a rough proxy for usage — see the caveats below.

Home sizeEst. annual useSystem size400W panelsRoof space
1,000 sq ft5,000 kWh3.6 kW9158 sq ft
1,200 sq ft6,000 kWh4.4 kW11193 sq ft
1,500 sq ft7,500 kWh5.5 kW14245 sq ft
2,000 sq ft10,000 kWh7.3 kW18315 sq ft
2,500 sq ft12,500 kWh9.1 kW23403 sq ft
3,000 sq ft15,000 kWh10.9 kW27473 sq ft

Solar panels needed by monthly electric bill

Your bill is often a better proxy than floor area. These rows convert a monthly bill into annual kWh at the US-average rate of 17¢/kWh, then size the system.

Monthly billEst. annual useSystem size400W panels
$80/mo5,647 kWh4.1 kW10
$120/mo8,471 kWh6.2 kW16
$160/mo11,294 kWh8.2 kW21
$200/mo14,118 kWh10.3 kW26
$250/mo17,647 kWh12.9 kW32
$300/mo21,176 kWh15.4 kW39

National-average modeled estimates, June 2026. Not a quote — see methodology.

The honest caveats

These numbers use US-average sun and consumption. Your real panel count depends on your roof's pitch and shading, your local sun hours, the wattage of the panels you choose, and — most of all — how much electricity you actually use. The fastest way to a precise figure is to run your last 12 months of usage through the savings calculator. To see how the cost scales, browse cost by system size, or check cost by state for prices and sun where you live.

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Frequently asked questions

How many solar panels does it take to power a house?
An average US home uses about 10,500 kWh a year. At roughly 549 kWh per 400-watt panel in an average US location, that's about 19 panels — a system of roughly 7.7 kW. Your real number depends on how much electricity you actually use, your local sun hours, and the wattage of the panels you install.
How many solar panels do I need for 1 kWh, or per day?
One 400-watt panel makes about 549 kWh a year, which is roughly 1.5 kWh per day on average. So a single good panel covers a bit more than 1 kWh of daily use. To cover, say, 30 kWh a day you'd need around 20 panels. Output swings with the seasons — more in summer, less in winter.
Do more solar panels always help?
Only up to a point. Sizing a system well past your annual usage produces excess energy that — depending on your state's net-metering rules — may be credited below the retail rate, so those extra panels pay back slowly. The best value is usually a system sized to roughly offset your own yearly consumption.
How much roof space does each solar panel need?
A standard 400-watt residential panel is about 17.5 sq ft. So a 20-panel system needs roughly 350 sq ft of usable, unshaded roof, plus some clearance around the array. Higher-wattage panels pack more output into the same footprint.