Solar guides
Practical answers backed by satellite data — no sales pitch.
How Many Solar Panels Do I Need? A Simple 3-Step Method
Calculate the number of solar panels for your home from your electricity bill, your location's sun hours and panel wattage — with worked examples.
Read the guide →Solar Payback Period: How to Calculate It Honestly
The real formula behind solar payback: system cost, self-consumption rate, electricity prices and degradation — plus typical payback times by region.
Read the guide →Best Tilt Angle and Orientation for Solar Panels (With Rules of Thumb)
Optimal tilt and azimuth for solar panels explained: latitude rules, east-west systems, seasonal adjustment and how much a wrong angle really costs.
Read the guide →GHI, DNI and DHI Explained: Which Solar Radiation Number Matters?
Global horizontal, direct normal and diffuse irradiance demystified — which metric to use for PV panels, trackers and CSP, and where the data comes from.
Read the guide →How Accurate Is PVGIS? What the Research Says
PVGIS accuracy compared with real production data: typical error margins, known biases, SARAH3 vs ERA5 databases and when to pay for a bankable study.
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