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Solar electricity calculator

System kW × peak sun hours × performance ratio for daily and yearly kWh. Swap the region to change default sun hours.

Defaults to your region. Switch to compare any other scale.

Result

20.25 kWh

Daily yield

  • Yearly yield7,391 kWh
  • Gross annual value1,183
  • PSH used4.5

Site matters more than the average

NREL PVWatts and similar tools use weather files, tilt, and azimuth. This page is the envelope math for first sizing.

About this tool

The solar electricity calculator estimates daily and yearly kilowatt-hours from system size (kW) and regional peak sun hours, adjusted by a performance ratio for real-world losses.

Peak sun hours differ by climate: northern Europe, India, Japan, Australia, and US averages ship as selectable defaults you can override. Panel count × wattage is only the start — shading, tilt, temperature, and inverter efficiency all sit inside the performance factor.

Figures are planning estimates, not a utility bill guarantee. Use them to compare regions or system sizes before you talk to an installer.

Formula

  • Daily kWh = kW × peak sun hours × PR
  • Year ≈ daily × 365
  • PR defaults to 0.75 (dust, heat, inverter)

How it is calculated

  1. Enter DC system size in kW.
  2. Peak sun hours default to the selected region — override if you have a local figure.
  3. Apply a performance ratio (0.75 is a conservative default).
  4. If your country, school or provider uses different rules, pick another option in the “Standard” menu at the top.

Questions

What is a peak sun hour?

One hour of 1,000 W/m² irradiance. Five PSH means the day’s energy equals five hours at peak sun, not five hours of clock time.

When should I change the “Standard” setting?

When the rules you work with differ from the default chosen for your language. Options on this page: Germany (~3.2 PSH); US sunbelt (~4.5 PSH); India (~5.5 PSH); Japan (~3.8 PSH); Australia (~5.2 PSH). The formula, steps and result update to match your choice.

Are the results official advice?

No. Calculate This is an educational tool. For important decisions, check primary sources or ask a qualified professional.

Sources

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