Which is greener?

majestic01

Hi All,
You advice/opinions please

I've been wondering which is greener, turning on my hot water as and when I need it or leaving it on constantly to maintain a supply?

Thanks

Penelope_Penguin

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chivers1977

Doesn't depend on whether you have a combi boiler or not. With my combi you just turn the tap on when you need it and it doesn't heat the rest of the time

slipp_digby

if its a storage cylinder it depends upon the standing losses from the cylinder against the energy to reheat the water (plus the inconvenience of having to wait)

loss are dependant upon temp of stored water (probably 60oC) level of insulation on the outside of the cylinder,
method of heating the water - gas or electric immersion heater
volume of water in storage cylinder
control of heat source - if the boiler interlocks out when heat is not required to maintain water temperature

if it a combi as above

Bongedone

As above but also the ambient air temperature helps dictate the hest loss.

Cardew

The heat losses from a well insulated hot water tank are surprisingly small. A full tank of hot water will lose heat equivalent to 2kWh to 3kWh in 24 hours(There are British Standard tests). As there will always be some hot water in the tank even if on a timer, the losses will be even lower.

It is also pertinent to point out that the heat is not 'lost' as it heats the fabric of the house which is useful much of the year - and why most HW tanks are in an airing cupboard.