Can I estimate the heat output of a device from WATTS?

If I have say, a radio, that uses 60W, can I estimate the heat output? According to what I have read, you multiply WATTS by 3.41 to give BTU/hour. So 60W = 204.6 BTU. But this can't all be output as heat can it? An 60W radio doesn't generate the same heat as a 60W light bulb. So is there any way to estimate heat output from power figures - or do you have to physically test with thermometers etc?