Plug-in solar savings & payback calculator
Estimate how much electricity a plug-in solar kit could produce, what it could save you each year, and how long it would take to pay for itself.
Enter your own numbers below. Every assumption is explained under the calculator, and you can change all of them. The result is an estimate, not a guarantee.
Advanced assumptions
How the calculator works
- Daily production = panel wattage ÷ 1,000 × peak sun hours × system efficiency. For example, 800 W × 4.5 hours × 80% ≈ 2.9 kWh per day.
- Yearly production = daily production × 365.
- Yearly savings = yearly production × share of solar power you use × your electricity rate.
- Payback = (kit price − rebates) ÷ yearly savings.
The assumptions, explained
| Input | Default | Why |
|---|---|---|
| Peak sun hours | 4.5 | A middle-of-the-range starting point. Your real value depends on location, panel direction and tilt; check it with PVWatts. |
| Electricity rate | 17¢/kWh | A placeholder only. Rates vary widely by state and utility, so use the rate from your own bill. |
| System efficiency | 80% | Panels rarely deliver their full rated wattage at your outlet because of inverter, temperature, wiring and soiling losses. |
| Share you use | 90% | Plug-in systems are usually sized to be used by the home as power is produced. Any power you don’t use may not earn a credit. |
Frequently asked questions
What are peak sun hours?
The number of hours per day that would deliver the same solar energy if the sun shone at full strength (1,000 watts per square meter). It is an average, not the hours of daylight.
Why is my result lower than the kit’s wattage suggests?
A kit’s wattage is measured in ideal lab conditions. Real output is lower because of heat, angle, shading, inverter losses and weather, which is what the efficiency setting accounts for.
Does a bigger kit always pay back faster?
Not always. If your home can’t use the extra power when it is produced, the extra output may earn nothing. That is why the “share you use” setting matters.
Is this financial advice?
No. It is a simple estimate based on the numbers you enter. Check your own bill, your utility’s rules and the product’s specifications before you buy.