Calculate the heat generated by any lighting installation — in watts, BTU/hr, and tons of refrigeration. Uses ASHRAE space fraction and radiative fraction to split heat between occupied space and ceiling plenum. Essential for HVAC sizing, energy modelling, and LED retrofit payback analysis.
Measurement units
Metric / SI
Watts, kW, °C
Imperial / US
BTU/hr, tons, °F
Space and installation
Office ~2500h/yr, retail ~4000h/yr, 24/7 ~8760h
Lighting fixtures
Fixture description
Count
W each
Please add at least one fixture and enter floor area.
Total heat to occupied space
0 W
0
Total lighting W
0
Heat to space
0
Annual cooling cost
0
W/m2 LPD
Heat flow breakdown — where does the lighting energy go?
Heat flow diagram — luminaire to space and plenum
Technology comparison — same lighting level, different heat loads
TechnologyLPD W/m2Heat WCooling $/yrSaving vs T8
Thermal load from lighting — key considerations
Total lighting load
Space fraction
Radiative fraction
Heat to occupied space
Heat to plenum
Annual cooling energy
Annual cooling cost
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