Solar Planning Calculators
Free, simple calculators that run in your browser. Use them to build your own rough estimate before you compare installer quotes.
Savings and system-size estimator
Enter your monthly bill, peak sun hours, roof space, roof direction and electricity price. The tool estimates how many panels you might need, the system size, annual production, monthly savings and a simple payback period.
Payback and ROI calculator
Enter the price from a real quote, any incentives you have confirmed you qualify for, and your expected monthly savings. The calculator shows the net cost, payback period and a simple 25-year return.
Carbon offset estimator
Enter a system size and choose the type of electricity it replaces to get an approximate yearly and 25-year CO2 reduction, with everyday comparisons.
Getting useful results
- Use twelve months of bills if you can; seasonal swings matter.
- Change one input at a time to see which assumptions drive the result.
- Only enter incentives you have confirmed are available to you today.
- Compare your result with each installer's production and savings figures, and ask about any large differences. Our planning FAQ lists the questions to ask.
Results are rough estimates based on simplified assumptions. They are not quotes and not financial, tax or engineering advice. See the disclaimer.