A BTU (British Thermal Unit) is the heat needed to warm 1 pound of water by 1 °F. BTU/h describes the heat transferred in one hour. The "9,000 BTU" and "12,000 BTU" figures quoted for air conditioners are actually BTU/h capacities: 12,000 BTU/h = 3.5 kW = 1 ton of refrigeration.
In industrial refrigeration BTU/h appears in imported compressor and evaporator catalogs, especially from American brands. To convert to kW, divide by 3,412: 60,000 BTU/h ≈ 17.6 kW. To convert to kcal/h, divide by 3.97. The kW–BTU/h page of the unit converter does the arithmetic quickly.
One point to watch is that some American catalogs give capacity at different operating conditions (for example 95 °F ambient, 45 °F evaporating). Converting the unit is not enough; the condition must also be interpreted against the European standard (32 °C ambient, a stated evaporating temperature). Otherwise the same unit appears with different capacities in two catalogs.