Estimate the solar system size needed for your home, cabin, RV, shed, or off-grid setup. This calculator estimates required solar kW size, solar panel count, daily production, monthly production, annual production, roof space, system cost, savings, and battery backup needs.
Daily usage mode:
The calculator uses your daily kWh use, solar offset goal, peak sun hours, and system efficiency to estimate the solar kW size needed.
Monthly usage mode:
The calculator converts monthly kWh into daily kWh, then sizes the solar system from that daily energy goal.
Electric bill mode:
The calculator estimates monthly kWh by dividing the electric bill by the electricity rate, then calculates solar system size.
Target production mode:
Enter a target monthly solar production amount to estimate the solar system size needed to produce that energy.
A solar system size calculator helps estimate how large a solar array should be before buying panels, comparing solar quotes, planning roof space, or sizing battery backup.
It can help compare system kW size, panel count, roof space, energy production, electric bill savings, system cost, incentive value, net cost, payback period, and battery capacity.
Your result shows the estimated solar system size in kilowatts, number of solar panels, total watts, expected daily production, monthly production, annual production, roof space needed, estimated monthly savings, annual savings, installed cost, incentive value, net cost, payback period, and battery backup size.
Divide your daily energy goal by peak sun hours and system efficiency. This gives an estimated solar system size in kilowatts.
For 900 kWh per month, that is about 30 kWh per day. The required system size depends on peak sun hours and losses. With 4.5 peak sun hours and 20% losses, the estimate is about 8.33 kW before rounding panel count.
Solar offset is the percentage of your electricity use you want solar to cover. A 100% offset means you want the solar system to produce roughly the same amount of energy you use.
The calculator includes system losses. Solar systems lose some output from inverter efficiency, wiring, heat, shade, dirt, panel angle, and real-world weather conditions.
No. This is an estimate for planning. Actual solar sizing should consider your roof layout, local solar resource, utility rules, shading, panel model, inverter design, and installer recommendations.