How many solar panels do I need for a 2000 sq ft house?

A typical 2,000 sq ft home in the US uses about 10,000 kWh annually. Depending on your location, you'd need roughly 18-25 panels rated at 400W each. Sunnier states like Arizona require fewer panels than northern regions like Minnesota.

What size solar panel system do I need to eliminate my electric bill?

To offset 100% of your electricity usage, match your system's annual production to your annual consumption. Most US homes need a 7-11 kW system. Net metering availability in your state determines whether you can truly zero out your bill.

Do south-facing panels produce more than east-west?

Yes, south-facing panels produce about 20-30% more energy than east or west-facing panels in the northern hemisphere. However, east-west configurations can still be effective and may better match afternoon energy usage patterns.

How accurate is this solar panel calculator?

The calculator uses NREL PVWatts methodology with real irradiance data for US locations. Actual production varies by 10-15% depending on shading, panel orientation, inverter type, and maintenance. Consider it a solid estimate for planning purposes.

Will partial shading significantly reduce my solar output?

Yes, even partial shading on one panel can reduce output by 25-40% for the entire string unless you use microinverters or power optimizers. Tree trimming or repositioning panels around shaded areas is often worth the investment.

Calculator

Solar PV Panel Calculator

Size your panels, output, and cost in under 2 minutes

Need to calculate solar panels for your home? This free solar PV calculator works out how many panels, what system size, and roughly what the system costs — all from your monthly electricity usage, roof area, and local sun exposure. It also estimates your solar panel output in kWh per year using NREL PVWatts v8 methodology, so you can calculate solar panel cost and production before talking to any installer. Whether you're planning a DIY installation or getting quotes from contractors, accurate sizing ensures you don't overpay for capacity you won't use—or underestimate what you actually need.

Enter Your Details

Fill in the form and click Calculate to see results.

Overview

Use this result

Use the calculator inputs first, then compare the result against local rates, incentives, roof conditions, and utility export rules.

Method, assumptions, and sourcesOpen this section when you want to audit the calculation behind the estimate.Show

Calculation Method

The calculator determines system size by dividing your annual energy requirement by the expected solar production per panel. We use the standard formula: System Size (kW) = Annual Energy (kWh) / (Peak Sun Hours × 365 × System Efficiency). Panel count is then derived by dividing system size by individual panel wattage, with a derating factor of 0.85 to account for real-world losses from inverter efficiency, wiring, temperature, and soiling—aligned with NREL PVWatts v8 recommendations. Peak sun hours are sourced from the National Solar Radiation Database for your specific US location. Estimated system cost is calculated from a regional cost per watt ($2.50–3.00/W typical for the US), so you can calculate solar panel cost before incentives in the same run. The tool also checks whether your available roof area can physically accommodate the calculated panel count, assuming standard 17.5 sq ft per 400W panel.

Key Assumptions

Solar panel count depends on annual kWh usage, usable roof area, local sun hours, inverter losses, and panel wattage.
Production estimates assume an unshaded roof section and typical residential system losses.
Final system sizing should be checked against installer layout, utility interconnection, and local code requirements.

How to Use This Calculator

Start by entering your average monthly electricity bill or kilowatt-hour usage—you can find this on your utility statement. Next, select your location from the US region dropdown, which adjusts solar irradiance data automatically. Enter your available roof space in square feet (measure the unshaded, south-facing portion). The calculator instantly shows how many panels you need, the recommended system size in kilowatts, estimated annual production, estimated cost before incentives, and whether your roof has sufficient area. Adjust panel wattage if you have a specific product in mind (400W is the default, reflecting current market standards).

Formula & Methodology

The calculator determines system size by dividing your annual energy requirement by the expected solar production per panel. We use the standard formula: System Size (kW) = Annual Energy (kWh) / (Peak Sun Hours × 365 × System Efficiency). Panel count is then derived by dividing system size by individual panel wattage, with a derating factor of 0.85 to account for real-world losses from inverter efficiency, wiring, temperature, and soiling—aligned with NREL PVWatts v8 recommendations. Peak sun hours are sourced from the National Solar Radiation Database for your specific US location. Estimated system cost is calculated from a regional cost per watt ($2.50–3.00/W typical for the US), so you can calculate solar panel cost before incentives in the same run. The tool also checks whether your available roof area can physically accommodate the calculated panel count, assuming standard 17.5 sq ft per 400W panel.

Frequently Asked Questions

Solar module prices average $2.50–3.00 per watt installed for US residential systems, so a typical 8 kW system runs about $20,000–24,000 before incentives. Using this calculator, the estimated cost comes from those regional cost-per-watt figures (solar module price per watt), so you see system cost before incentives in the same run. The 30% federal tax credit (subject to current-year eligibility rules) brings the net figure down further in qualifying tax years.

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