This is an economic analysis of indoor temperature and of short changes in indoor temperature. The loss of benefit is higher during short involuntary changes than during a voluntary chosen indoor temperature. There will be a short involuntary change in the indoor temperature if the design heating capacity doesn’t cover the heat demand during a cold period. A one-day cold period is to short for design of heating capacity. The loss of benefit from low temperatures during one day will not be so high that it motivates a heating system. The increase of loss of benefit during short involuntary changes in indoor temperature may be 10 times higher than during voluntary changes, if the present Swedish design rules for heating capacity are economically optimal. The loss of benefit at the indoor temperature 22degreesC is 0.2 % of the disposable income per day of heating season. If the temperature is voluntary changed to 20degreesC the loss of benefit will be 0.9 %. A short involuntary change to 20degreesC will increase the loss of benefit to 3.1 %.