Solar Array Energy Calculator
Daily, monthly and yearly PV energy — panels × watts × your site’s peak sun hours × your performance ratio — with specific yield, value and offset.
The kWh a given array should produce at your site under the figures you supply, what that is worth at your tariff, and what share of your use it covers — with no climate data or loss factor assumed for you.
Example: Twenty 400 W panels are 8 kWp. At 4.5 peak sun hours and an 80 % performance ratio (both your site’s figures) that is 28.8 kWh a day, 10,519 kWh a year — 1,315 kWh per kWp — worth 2,630 at 0.25/kWh.
Nameplate, sun,
and everything lost between.
The one-line yield model, where its two site figures come from, and what it cannot tell you.
The model
A panel's watt rating is its output at standard test conditions (1,000 W/m², 25 °C). “Peak sun hours” is the day's irradiation on the array plane expressed as hours at that 1,000 W/m² — numerically the kWh/m²/day your site receives at the array's tilt and orientation. Multiplying the array's kWp by peak sun hours gives the energy an ideal array would make; the performance ratio scales it for everything real — panel temperature, soiling, shading, mismatch, wiring, inverter conversion and downtime — as IEC 61724 defines it. Daily × 365.25 is the year.
Your two site figures
Both are yours to supply and the page embeds neither: peak sun hours come from an irradiance dataset or a solar-resource map for your location and tilt (annual average, or a month at a time), and the performance ratio from your installer's design, a neighbouring system's monitoring or, once running, your own meter (energy ÷ nameplate ÷ irradiation). Specific yield — kWh per kWp per year — is reported because it is the number installers and monitoring portals quote and lets you sanity-check the inputs against a real system nearby.
What it does not decide
Sizing, string design, inverter choice, export limits, feed-in rules, incentives and payback are not modelled; the value figure is energy × the single tariff you enter and the offset is energy ÷ your daily use, with no self-consumption or export split. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- IEC 61724-1:2021 — photovoltaic system performance: reference yield, final yield and performance ratio definitions (cited as the framework; no values reproduced)
- Peak sun hours (plane-of-array irradiation) and performance ratio are site-specific user inputs; no irradiance database or loss defaults are embedded
Last reviewed 19 September 2026. How results are checked: How we verify.