Solar panel
Location
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Share of the panels' rated output that reaches the load on the direct path. Covers inverter or charge-controller conversion, cells running hotter than 25 °C, wiring and mismatch, dirt and shading. Not cell efficiency: that is already inside the kWp rating. Real systems land at 75–85 %; PVGIS assumes 86 %.
Click or drag the compass to set direction, and the side view to set tilt.
Estimated output
Clear-sky model (Meinel beam, Haurwitz global, isotropic diffuse and ground reflection), scaled month by month to match NASA POWER's measured irradiance for the site. Absolute numbers are indicative; the comparison between orientations is robust.
Annual output by tilt and direction
Hover to read values, click to set the panel orientation. Circle = current, star = optimum.
Daily power profile (solar time)
Monthly output
Show as table
Battery
Pick a battery or describe one. The reserve and the state of charge through the year follow from the panels above and the usage below.
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How much of the rated capacity the system may draw before it stops supplying the load. The rest is never touched, which protects the battery from deep discharge. The state-of-charge chart shows the usable part, so 0 % there means the reserve is spent, not that the cells are flat. LiFePO₄ 80–90 %, Li-ion about 80 %, lead-acid 50 %.
Extra loss for energy that goes through the battery instead of straight to the load: cell chemistry plus the charge and discharge electronics. Applied half on the way in and half on the way out. Do not include the inverter here if it is already in the performance ratio. Lithium cells 90–95 %, lead-acid about 80 %.
State of charge through the day (solar time)
State of charge through the year
Usage
Paint the power used hour by hour on a typical day, and see whether the panels and battery keep it powered through the year. Hours are in solar time.
Monthly energy balance
Show monthly table
Cost & return
Hourly import and export prices, what the panels and battery cost, and what the system saves over its life. Prices in p per kWh, costs in £. Hours are in solar time: UK clock time is about the same in winter and one hour later in summer.