These are completely different units of measurement. KW – kilowatt, an abbreviation for a unit of power; 1 kW equals 1000 watts. It is often used to describe electrical devices as their actual power. KWh – kilowatt-hour, a unit of energy, heat, and work; the amount of energy consumed per hour by a device with a power of 1 kilowatt (1000 watts). It is most often used in billing with the power company as the actual electricity consumption. KVA – kilovolt-ampere, an exception being made for generators and UPSs, where this term is used instead of watts or kilowatts.
This is a unit of apparent power, i.e., real power + reactive power. Generator power is measured in kVA, and 1 kVA is assumed to equal 0.8 kW. However, this is not a constant value, but rather a variable value, depending on the devices connected to the generator. More information can be found here.