During 3 hours one winter afternoon, when the outside temperature was 7° C (32° F), a house heated by electricity was kept at 19° C (68° F) with the expenditure of 60 kwh (kilowatt·hours) of electric energy.
2007-03-15 18:03:16 · 2 answers · asked by lank s 1 in Science & Mathematics ➔ Physics
60 kwh over 3 hours is 20 kw, not 20 kw/hr. 20 kw is 20000 Joules/sec by definition or 20 kJ/sec. That sounds like a lot, but in terms of fuel usage, that heat is equal to about 1.5 gallons of gasoline (or propane) over the three hours. Of course, being it was electric heat it takes about 3 times that much fuel to produce the electricity.
2007-03-15 18:23:48 · answer #1 · answered by Pretzels 5 · 1⤊ 0⤋
OK. 60kwh over 3 hours is 20 kw / hour which is
20,000/3600 = 5.555 J/s lost through the walls.
HTH âº
Doug
2007-03-16 01:09:41 · answer #2 · answered by doug_donaghue 7 · 0⤊ 0⤋