This New Zealand calculator estimates what your hot water costs to run, one of the biggest slices of a power bill. You enter household size, water heating type and your power price, and it shows the annual cost and how changes like shorter showers or a heat pump cylinder would reduce it.
Hot water energy per person is a rough average; heavy shower use raises it. The heating type adjusts for efficiency, with a heat pump cylinder using a fraction of a standard element. Power prices change, so use your current rate. Estimate only.
The calculator estimates the energy used to heat water as the people times the energy per person, adjusted for the efficiency of your water heating type, then multiplies by your power price across the year. A standard electric cylinder uses one unit of power per unit of heat, while a heat pump cylinder delivers the same hot water for far less, which is why it shows a much lower cost.
A 3-person household using 3.5 kWh each a day with a standard electric cylinder at 28 cents costs about $1,073 a year. A heat pump cylinder, around three times as efficient, would deliver the same hot water for roughly $358, showing the saving on offer.
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