The BTU (BRITISH THERMAL UNIT) is the unit of energy used in the USA and the UK, used in defining the cooling power of air conditioning systems as well as the heating value of fuels.
To convert W to BTU/h, it is sufficient to know that 1 W corresponds to 3.41 BTU/h. So to convert BTU/h to Watt you divide by 3.41; to convert Watt to BTU/h you multiply by 3.41.