| Space Type | Max LPD (W/ft²) |
|---|---|
| Office | 0.64 |
| Classroom / Lecture | 0.71 |
| Retail | 1.05 |
| Warehouse | 0.33 |
| Corridor / Transition | 0.41 |
| Lobby / Atrium | 0.90 |
| Conference / Meeting | 0.97 |
| Healthcare Patient Room | 1.07 |
| Dining | 0.65 |
| Restroom | 0.63 |
This lighting heat gain calculator finds the sensible cooling load that interior lighting adds to a space. Enter the room area, lighting type, lighting power density, ballast or driver factor, and use factor; the tool returns connected power, total heat gain, the cooling load after a cooling-load-factor adjustment, the radiant and convective portions, and the equivalent tons.
Lighting is a core internal gain in a cooling load calculation, and its radiant share appears as a delayed load. The page also checks the design lighting power density against ASHRAE 90.1-2019 limits so you can confirm energy-code compliance at the same time.
| Quantity | Equation |
|---|---|
| Total power | W = Area × LPD × Ballast × Use factor |
| Total heat gain | BTU/hr = W × 3.412 |
| Radiant / convective | Radiant = BTU × f⁵ ; Convective = BTU × (1 − f⁵) |
| Cooling load | CL = Convective + Radiant × CLF |
The 3.412 BTU/hr per watt conversion is exact. The radiant fraction f⁵ (LED ≈0.37, fluorescent ≈0.54, incandescent ≈0.87) splits the gain into a delayed radiant part and an immediate convective part, per ASHRAE Fundamentals heat-gain methodology. The cooling load factor (CLF) is applied to the radiant portion only to account for thermal storage lag. The compliance check compares LPD × ballast to ASHRAE 90.1-2019 space-by-space limits.