The kilowatt hour (symbol kWh, kW?h, or kW h) is a derived unit of energy equal to 3.6 megajoules.If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time in hours. The kilowatt-hour is commonly used as a billing unit for energy delivered to consumers by electric utilities. The symbol "kWh" is commonly used in commercial, educational, scientific and media publications, and is the usual practice in electrical power engineering. Other abbreviations and symbols may be encountered: "kW h" is less commonly used. It is consistent with SI standards (but note that the kilowatt-hour is a non-SI unit).
The international standard for SI states that in forming a compound unit symbol, "Multiplication must be indicated by a space or a half-high (centered) dot (?), since otherwise some prefixes could be misinterpreted as a unit symbol" (i.e., kW h or kW?h).This is supported by a voluntary standard6 issued jointly by an international (IEEE) and national (ASTM) organization.
However, at least one major usage guide and the IEEE/ASTM standard allow "kWh" (but do not mention other multiples of the watt hour).One guide published by NIST specifically recommends avoiding "kWh" "to avoid possible confusion". The US official fuel-economy window sticker for electric vehicles uses the abbreviation "kW-hrs". Variations in capitalization are sometimes seen: KWh, KWH, kwh etc. "kW?h" is, like "kW h", preferred with SI standards, but it is very rarely used in practice. The notation "kW/h", as a symbol for kilowatt-hour, is not correct. Źródło: https://en.wikipedia.org/wiki/Kilowatt_hour.