CalcArcade.

Solar Panel Output Calculator

Enter the size of a solar system and your local peak sun hours to estimate how much electricity it makes, what that is worth on your bill and how long it takes to pay for itself.

Your numbers

Result

How we calculate it

Annual energy = system size in kW × peak sun hours per day × 365 × efficiency. A peak sun hour is one hour of sunlight at 1,000 watts per square meter, so 5 peak sun hours means your panels receive the energy of 5 hours of full sun on an average day.

Efficiency, sometimes called the performance ratio, bundles the real-world losses between the panels and your outlet: inverter conversion, wiring, heat, dust and shading. A range of about 75% to 85% is common for planning.

Yearly value is annual kWh × your electricity price. Simple payback is the installed cost divided by that yearly value, with no incentives, financing, rising prices or panel aging included.

Assumptions and limits

  • Peak sun hours depend on location, season, roof tilt and direction. Use a local figure for a better estimate.
  • Assumes every kWh is worth the same price to you. Net metering and export rates differ by utility.
  • Ignores tax credits, rebates, financing, electricity price changes and the slow loss of panel output over the years.
  • A planning estimate, not a quote. An installer can model your actual roof.

Frequently asked questions

How many kWh does a 6 kW system make in a year?

With 5 peak sun hours and 80% efficiency it makes about 8,760 kWh a year, roughly 730 kWh a month.

How do I find my peak sun hours?

They depend on where you live and how the panels are mounted. National laboratories and many installers publish location-based solar resource maps and tools you can look up by address.

Does payback include incentives?

No. Incentives, rebates and financing vary widely, so this shows the plain cost against yearly savings. Your real payback may be shorter.

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Worked example (a fixed example using the starting numbers, it does not change as you type)

Inputs: System size (kW) = 6; Peak sun hours per day = 5; System efficiency (%) = 80; Electricity price ($ per kWh) = 0.16; Installed cost ($) = 18000.

  • Energy per year 8,760 kWh
  • Average per month 730 kWh
  • Average per day 24.0 kWh
  • Value per year $1,401.60
  • Simple payback 12 years 10 months
  • Payback in years 12.8

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Last reviewed: . Formulas and assumptions are described on our methodology page. For information only; not professional advice.