Independent energy/ CALCULATOR
Hot-water recirculation energy and cost
Estimate annual pump electricity and the energy needed to replace heat lost from a hot recirculation loop.
Use measured electrical input or the pump nameplate input, not hydraulic output.
Use controller history or measured average daily run time.
Add the heated supply and return sections of the recirculation loop.
Use a design or measured value for the actual pipe size, insulation, water and ambient temperatures.
Include the cooling period after the pump stops, not only pump motor run time.
Useful heat restored to the loop divided by purchased heater energy.
Use the number of days the recirculation system is enabled.
Use the relevant electricity or delivered-energy price.
Annual pump electricity
3.0 kWh/year
Annual heat lost from the loop
219.0 kWh/year
Purchased energy replacing pipe heat
243.3 kWh/year
Total purchased operating energy
246.4 kWh/year
Estimated annual operating cost
49.28 currency/year
Constant average pump power and linear pipe heat loss during the entered hot-loop time. The heating efficiency is applied only to replacement heat, while pump electricity is added directly. Start-up transients, tariff tiers, heater standby loss, control power and heat that usefully warms the building are excluded.