This is a timer unit, so let’s assume it is on 3 hours per day (5am-6am, 5pm-7pm). This unit uses 100 watts. This equals 0.3 kWh per day or 110 kWh per year. At $0.12/kWh, this comes out to $13.14 per year.
Next, let’s look at heat loss. Heat is transferred to the water via the hot water heater/boiler. Because the hot water recirculator is constantly pushing hot water through the pipe system, heat has the opportunity to escape the water through the metal pipes. Because of this, the heater/boiler has to work extra hard to keep the water hot.
Heat loss from the pipe is 35 Btu/hr ft (assuming a temperature difference of 55 degrees). We’ll say that the distance from the water heater to your faucet is 50 feet. So we take 35 Btu/hr ft * 50 ft * 1,095 hours and end up with 1,916,250 Btu of heat loss that must be replaced by the heater. 1,916,250 Btu = 20 therms = 586 kWh = $70.30/year
In this article, we calculated that we would save at least 5,000 gallons per year. Water costs $3.50 per 780 gallons which comes out to $23/year in water savings
Hot Water Recirculator: -$191
Electricity for Recirculator: -$13.14/year
Heat Loss: -$70/year
Water Savings: +$23/year