Yes, instant geysers consume a significant amount of electricity. As their wattage ratings are usually 3000 W to 4500 W, they consume 3 to 4.5 units of electricity per hour when you need hot water consistently. But, if you keep the geyser in idle condition, it won't consume much energy as the thermostat will cut off the power when it reaches a preset temperature. We will also advise you to get an instant heater with high energy efficiency ratings to cut down on energy bills.