About the irradiance estimate

Every solar and diesel figure on a site's design is only as good as the sunlight data behind it. When a site has no real, measured irradiance imported, the dashboard falls back to a latitude-band estimate — a reasonable approximation based on where in the world the site sits, not a measurement of that specific location's actual weather history. Every figure derived from it is indicative only, not a guarantee.

Why this matters more than it might seem. Fuel is usually the single largest ongoing operating cost on an off-grid or hybrid site. The solar fraction the estimate assumes flows directly into how much diesel the design expects to burn — and therefore into the tariff or budget built on top of it. An estimate that's off by even a modest amount can make a real difference to whether a design is profitable once it's actually running.

What to do about it. Import real irradiance data for the site before pricing a tender or committing to a fuel budget:

• NASA POWER — free, global, no account required. Good default source for most sites.
• PVGIS — the European Commission's solar resource tool, strong coverage across Europe, Africa, and much of Asia.
• A site survey with a real pyranometer, if the project justifies the cost.

Once real monthly irradiance is imported for a site, this warning is replaced with a note confirming measured data is in use, and every solar/diesel figure recomputes against it automatically — nothing else about the design needs to change.