Heat loss & emitters
Solar thermal useful-power estimate
- where
- useful power (W; the calculator shows kW)
- collector area (m²)
- incident irradiance (W/m²)
- collector efficiency (fraction; any unit you pick is converted)
Explain this equation
Gives a snapshot of the useful heat a solar thermal collector array delivers. Use it for quick output checks at particular conditions.
A is the collector area on the basis the efficiency is quoted for, such as gross or aperture area. G is the solar irradiance hitting the collector, in watts per square metre. η is the efficiency at those operating conditions, the fraction of incident sunlight converted to useful heat.
Incident solar power is area times irradiance. Multiply by efficiency to get the useful share. The calculator shows kW.
Sense check: 4 m² at 800 W/m² and 50% efficiency gives 1.6 kW. Bright sun is around 800–1000 W/m²; overcast may be under 200.
Watch out: efficiency falls as the collector runs hotter than the air. This is not an annual yield calculation.
Enter your values to see the result.
Good to know
A snapshot using supplied operating efficiency. Not an annual-yield, stagnation or safety calculation.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.