We take advantage of a natural experiment in the state of Indiana to estimate the effect of daylight saving time (DST) on residential electricity consumption. Our main finding is that, contrary to the policy's intent, DST increases electricity demand. The findings are consistent with simulation results that identify a trade-off between reducing demand for lighting and increasing demand for heating and cooling. We estimate a cost to Indiana households of $9 million per year in increased electricity bills. We also estimate social costs of increased pollution emissions between $1.7 to $5.5 million per year.