Free tool
Cellar cooling calculator.
How much cooling your cellar actually needs, in BTU/h, from the things that drive it: volume, insulation, glass, the temperature on the warm side, and how often the door opens. Brand-neutral. The number is the same whatever you end up buying.
How it is calculated
I
Conduction
Heat through each surface is area × temperature difference ÷ R-value. Walls, ceiling, floor, and glass are computed separately, so a glass wall shows up as the load it really is.
II
Air
A sealed room still exchanges about half its air every hour, and each door opening swaps roughly half the room. Incoming air carries moisture the unit must condense, so the air terms include that latent load.
III
Margin
A cellar unit should carry the steady load at roughly half duty, with reserve for pull-down. The recommendation applies that margin. Oversizing beyond the shown range short-cycles the compressor and leaves the room humid.
This is an estimate for a sealed, vapour-barriered room with no direct sun. Thermal bridging, a missing vapour barrier, or a south-facing glass wall can push the real load well above it. For the reasoning behind each term, read How to size cellar cooling. Unsure about your numbers? Contact our experts.