Use this free Solar PV Calculator to estimate the solar system size you may need based on your monthly electricity usage, peak sun hours, panel wattage, and system efficiency. This calculator can help you get a simple first estimate before speaking with a solar installer or reviewing a professional solar proposal.

To use the calculator, enter your monthly electricity usage in kWh, average peak sun hours per day, solar panel wattage, system efficiency, and electricity rate. The calculator will estimate the solar PV system size in kilowatts, recommended number of panels, estimated monthly solar production, electricity offset, and potential monthly and yearly value.

Solar PV system sizing depends on how much electricity your home uses and how much sunlight your location receives. Homes in sunnier areas may need a smaller system to produce the same amount of electricity compared with homes in areas with fewer peak sun hours.

The default electricity rate is set to $0.17 per kWh as a general U.S. residential estimate. You can change this value based on your own utility rate for a more personalized estimate.

Solar PV system size is estimated by comparing your daily electricity usage with the amount of solar energy your location can produce.

Daily electricity usage = monthly electricity usage ÷ 30

Required solar system size = daily electricity usage ÷ peak sun hours ÷ system efficiency

Number of solar panels = required system size ÷ panel size

For example, if your home uses 900 kWh per month, your average daily usage is 30 kWh. If your location receives 5 peak sun hours per day and the system efficiency is 80%, the estimated system size would be about 7.5 kW.

Actual solar production can vary based on location, roof direction, roof angle, shading, panel efficiency, inverter efficiency, temperature, weather, and system design. Even two homes with the same monthly electricity usage may need different solar system sizes depending on roof conditions and sunlight exposure.

Solar savings also depend on your electricity rate, utility rules, net metering policy, fixed charges, and how much of the solar energy is used directly by the home.

This calculator provides a simplified estimate only. It is not a replacement for a professional solar design or site assessment. Actual solar PV system size, production, cost, and savings may vary depending on location, roof conditions, utility rules, equipment, permits, and installer design.

Solar PV stands for solar photovoltaic. It refers to solar panels that convert sunlight into electricity.

The number of panels depends on your monthly electricity usage, panel wattage, peak sun hours, and system efficiency. Higher electricity usage usually requires a larger solar system.

Peak sun hours estimate how much usable sunlight your location receives per day. Sunnier locations usually have more peak sun hours and can produce more solar electricity.

No. This calculator gives a simplified estimate. A professional solar installer should evaluate your roof, shading, utility rules, and electrical system before final sizing.

Solar systems have real-world losses from inverters, wiring, temperature, dirt, shading, and other factors. Efficiency helps account for those losses in a simple way.

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