Oil-filled radiators vs fan heater. What does KW mean?

It takes the same amount of energy to heat one cubic foot if air one degree regardless of what KW you use. the problem with the 2KW is that you experience heat loss at a same rate also. It is doubtful that the 2KW could keep with the heat loss.Therefore the 2KW would run constantly, without increasing the temperature. The 700KW would use more energy per minute of on time, but would run less time than the 2KW. The economic side of this is, how many 2KW heaters will it take to heat your home? Think of it this way. On a gas stove the pilot light burns constantly (2KW), but to heat water you must increase the gas flow (700KW). The water would never boil with just the pilot.