Doing for a drive to the countryside for a walk? Having a long and relaxing bath? Go-karting? Using a heated pool? Keeping the heater on a single house-level timer so they don't have to think about it rather than planning ahead what rooms they will be in later?
Everyone will have a different place they draw the "waste" vs sensible expenditure line.
The correct economic solution to this is CO2-offsetting taxes and letting each individual decide how they want to spend their resources. Trying to centrally plan for a hundred million diverse people with different things they like and care about is a recipe for unneeded misery.