Yes, tankless water heaters require a lot of electricity – but they don’t run all the time, so electricity is only used when you turn on your hot water faucet. The average tankless heater uses around 30,000 watts of electricity when it’s switched on. To put this into perspective, a washing machine needs only about 1,000 watts to run for over an hour. But you’ll still save energy with a tankless water heater because it only switches on when needed.