Solar Panel Calculator

Enter your monthly electricity usage (kWh), location's peak sun hours, and system details like efficiency and desired offset to calculate your recommended solar panel system size. You'll get back the total kW needed, estimated number of panels, approximate system cost, and projected annual savings — all in one place.

kWh

Check your electricity bill for average monthly kWh usage.

USD

Used to estimate your annual savings.

hours/day

Typically 3–6 hours depending on your location. Southern states average 5–6 hrs.

100% offsets your full electricity usage. Choose more to account for future growth.

%

Accounts for wiring, inverter, and temperature losses. 14% is a standard estimate.

W

Modern residential panels range from 350W to 450W.

$/W

Average installed cost in the US is $2.50–$3.50 per watt before incentives.

Results

Recommended System Size

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Number of Panels Needed

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Estimated System Cost

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Cost After 30% Federal Tax Credit

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Estimated Annual Savings

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Estimated Payback Period

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Annual Energy Generated

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System Cost Breakdown

Frequently Asked Questions

How many solar panels does the average home need?

Most American homes use between 800–1,200 kWh per month and require a 6–12 kW solar system. Using 400W panels, that translates to roughly 15–30 panels. Your exact number depends on your electricity usage, roof orientation, local sun hours, and how much of your bill you want to offset.

What are peak sun hours and how do they affect my system size?

Peak sun hours represent the number of hours per day when sunlight intensity averages 1,000 W/m² — the standard used to rate solar panels. The more peak sun hours your location receives, the more energy each panel produces daily, meaning you need fewer panels. Southern US states average 5–6 hours while northern states may see 3–4 hours.

What is the federal solar tax credit and how much can I save?

The federal Investment Tax Credit (ITC) allows homeowners to deduct 30% of the total solar installation cost from their federal taxes. For a $18,000 system, that's a $5,400 reduction in your tax liability. This credit is currently available through 2032 for residential installations.

How accurate is this solar panel calculator?

This calculator provides a solid ballpark estimate based on your inputs. Real-world results can vary based on your roof's pitch, shading from trees or buildings, panel brand and quality, local utility rates, and installer pricing. For a precise quote, get assessments from 2–3 local solar installers.

What is the typical payback period for a home solar system?

The average payback period for residential solar is 6–12 years, depending on your local electricity rates, system cost, and available incentives. After the payback period, you essentially generate free electricity for the remaining 15–20 years of the system's lifespan.

Should I size my solar system to cover 100% of my electricity usage?

Many homeowners aim for 100% offset, but sizing to 80–90% is sometimes more cost-effective since the last few peak-demand hours can be expensive to cover fully. If you plan to add an electric vehicle or heat pump in the future, sizing at 110–125% now can be a smart investment.

What system losses should I account for in my solar calculation?

Real-world solar systems lose efficiency due to wiring resistance, inverter conversion losses, soiling, temperature effects, and shading. A standard estimate is 14% total system losses. Snow-prone areas may use 15–18%, while optimal conditions might be closer to 10–12%.

How long do solar panels last?

Most modern solar panels come with 25–30 year performance warranties and are designed to last 30+ years. Over time, panels degrade slightly — typically losing about 0.5–0.7% efficiency per year. After 25 years, a quality panel should still operate at around 80–85% of its original rated output.

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