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Free Solar Sizing Tool

Solar Panel Calculator

Estimate the solar system size, number of panels, inverter capacity, battery storage, energy production, installation cost, and potential electricity savings for your property.

Enter Your Solar Requirements

Adjust the values below according to your electricity usage, location, preferred panel rating, and local installation prices.

Enter the kWh shown on your monthly electricity bill.
Most sunny regions receive approximately 4 to 6 peak sun hours.
Choose the rated output of one solar panel.
Accounts for heat, wiring, dust, inverter, and shading losses.
Select how much of your consumption solar should cover.
Enter your electricity rate in your preferred currency.
Include panels, inverter, structure, wiring, and labor.
Calculations use the rate and cost values entered above.
Enter zero if you do not plan to install battery storage.
Larger residential systems commonly use a 48V battery bank.
The calculator assumes approximately 2.6 square meters per modern panel.
Please enter valid positive values in all required fields.

What Is a Solar Panel Calculator?

A Solar Panel Calculator is an online estimation tool that helps determine the approximate size of a solar energy system required for a home, office, shop, or other property. It uses your electricity consumption and local sunlight conditions to estimate how much solar capacity you may need.

This calculator also estimates the number of solar panels, inverter capacity, battery storage, roof area, annual electricity production, installation cost, potential savings, and simple payback period.

System Size Estimate

Calculate the solar capacity needed to cover your selected percentage of electricity consumption.

Panel Requirement

Estimate how many solar panels are needed based on the wattage of each selected panel.

Cost and Savings

Compare estimated installation cost with annual electricity savings and the simple payback period.

How to Use the Solar Panel Calculator

1

Enter Monthly Electricity Usage

Find your monthly electricity consumption in kilowatt-hours on your latest utility bill and enter it in the calculator.

2

Add Peak Sun Hours

Enter the average peak sun hours available in your location. This is different from the total number of daylight hours.

3

Select Panel and Efficiency Values

Choose the wattage of the panel you plan to use and select a realistic overall system efficiency.

4

Enter Local Energy and Installation Costs

Add your electricity rate and estimated installation cost per watt in the same currency.

5

Calculate and Review the Results

Select the Calculate Solar System button to view the recommended capacity, panel count, battery storage, cost, and savings.

How the Solar Panel Calculation Works

The calculator first converts monthly electricity consumption into average daily consumption. It then divides the required daily solar energy by peak sun hours and system efficiency.

Basic solar system size formula

Solar System Size = Daily Energy Requirement ÷ Peak Sun Hours ÷ System Efficiency

Solar Panel Count

The required system capacity in watts is divided by the wattage of one panel. The result is rounded up because a partial solar panel cannot be installed.

Panel count formula

Number of Panels = Required System Watts ÷ Panel Wattage

Battery Capacity Estimate

Battery storage is estimated from average hourly electricity use and the selected backup duration. The calculator includes an allowance for battery depth of discharge and conversion losses.

Factors That Affect Solar System Performance

Real solar production can differ from calculator estimates. Roof direction, panel tilt, seasonal sunlight, shade, high temperatures, panel degradation, inverter efficiency, dust, wiring losses, and maintenance can all affect actual performance.

A qualified solar installer should inspect the property, review load patterns, assess structural conditions, check electrical equipment, and confirm local requirements before installation.

Frequently Asked Questions

The number of panels depends on your electricity usage, peak sun hours, panel wattage, system losses, and desired energy coverage. Enter these details in the calculator to receive an estimate.

Peak sun hours represent the equivalent number of hours per day when solar radiation averages 1,000 watts per square meter. They are not the same as total daylight hours.

An overall efficiency of around 75% to 85% is commonly used for an initial estimate. It accounts for inverter, wiring, temperature, shading, dust, and other energy losses.

No. A grid-tied solar system can operate without batteries when the electrical grid is available. Batteries are useful when you need backup power or want to store excess solar energy.

Panel dimensions vary by model. This calculator uses approximately 2.6 square meters per panel, including a practical allowance for installation spacing and access.

No. The cost is based on the price per watt entered by the user. Equipment brands, batteries, roof work, permits, taxes, labor, mounting structures, and grid connection charges may change the final price.

It provides a useful preliminary estimate based on standard formulas. A professional site survey and detailed engineering assessment are still required for final equipment selection and installation.