> Isn't the waste energy from the inefficiency of the incandescent bulbs fully deposited in your house? Yes, and that mean an incandescent bulb is 100% efficie

> Isn't the waste energy from the inefficiency of the incandescent bulbs fully deposited in your house? Yes, and that mean an incandescent bulb is 100% efficient: all power used is converted to light+heat. But other systems can be more than 100% efficient - they can add more heat than the power they use. Or, in the case of central heating from waste, unused heat will probably have to be pumped off anyway, so using it is energetically free.