There have been recent discussions within the “modern wood heat” industry about the advantages of referring to boiler output in kW as opposed to the traditional BTU/hour. Both kW and BTU/H are units used to measure power, and so they convert easily from one to another. One kW = 3,412 BTU/Hr. kW is a term that is commonly used to measure electrical power, both here in North America, and abroad. A kW is 1000 Watts, and one thousandth of a Megawatt. kW is also commonly used to refer to thermal power (heat) in Europe, whereas here we are still using British Thermal Units per hour (BTU/H) to refer to heating systems (e.g. boiler and furnace output) due to the inertia of longstanding habit.
The reason why kW might be a better reference unit of power for pellet boilers is that it gives people a unit that is also used for solar PV. As more and more people research ways to reduce their carbon footprint, they might want to weigh an investment in biomass thermal (e.g. wood pellet boilers) against an investment in solar PV (solar panels). Using dollars invested per kW produced would be a good way to make the comparison.