People are prone to habits but how important are they for economic outcomes? In a randomized field experiment we compare two treatments with identical economic incentives to adjust a range of household production activities. Treatments only differ in the extent to which they allow households to adjust habits relevant for these activities. We utilize smart-metered hourly power consumption to unobtrusively measure treatment effects. We find that preventing habits from being adjusted reduces consumer surplus by 76% suggesting a substantial economic value of habits.