Reply To: Very high energy bill in 8 year old house – no apparent cause

[Ian McChesney]

Hi Phil
Re your HW system I think there are some issues that are impacting on your high power bill, and some that aren’t. The faulty thermostat will be – hotter water will cause higher standing losses from the HW cylinder (maybe an additional 1-2kWh/day), and extra losses associated with the vent pipe, the waste hot water that sits in pipes after hot water is used etc. However, the undersized element, on its own, shouldn’t be adding to power bill. For example, if after a couple of showers the HW cylinder needed to heat 115 litres of cold water up to 60degrees, that would require about 6kWh. A 1.5kW element would take 4 hours to reheat; a 3kW element would take 2 hours. The energy use is the same. Undersized elements tend to add to frustration and poor hot water service rather than the power bill.

If you suspect the element is turning on frequently to maintain temperature it suggests there is excessive heat loss or water loss occurring – poor tank insulation, faulty pressure reducing valve (if fitted), a water leak, or back to the thermostat.
regards
Ian

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