A nice teardown of one here :I always wondered if those pass-through-plug power meters that do do kWh were just internally a CT clamp around the passed through live..
A nice teardown of one here :I always wondered if those pass-through-plug power meters that do do kWh were just internally a CT clamp around the passed through live..
How long does it take for the sum costs of standing losses of a tank of hot water, pipes to the tap, plus a need to run off X litres of cold down the plug hole before the hot arrives to breach £100? And what's the convenience of instant hot water worth versus the inconvenience of losing under-sink cupboard space?But is it worth £100 plus to fit one
Plug hole, never, goes in a bucket for later use in the looplus a need to run off X litres of cold down the plug hole before the hot arrives
But you are not comparing apples with apples, if you want to know the true figure you need to heat the whole tank with electric to compare it with gas which is heating the whole tank, what is your HW usage if only the top section is heated and is adequate ?
If you use 25kwh/day of gas and assuming you are heating water from 10C to 45C, and assuming a 85% boiler efficiency then this equates to heating and using 522 litres/day, very unlikely even if you are loosing a max of 2kwh/day through the cylinder then you are heating and using well over 500 LPD.The, very rough, experiment is complete.
With the "warm days" for the last two days. I decided to do an experiment. I turned off heating and hotwater via the boiler and only used an immersion heater set so that the hot water was "hot but touchable", about 45degrees (Yes, I know I should be hitting 60 for legionaries). With the immersion on pretty much all day, relying on it's own thermostat to keep the top 1/4 of the tank hot, it used in total an extra 7 to 8 KWH above my baseline daily use.
From my records my gas boiler would use about 25KWH, heating the whole tank (100L) twice in a day to a similar temperature. There would be extra "losses" here from heating the whole tank rather than (approximately) 25litres. In addition, with it being a gravity circulation on the hot water, there is no valve preventing some losses to the nearest radiator (unless I turned them off). There is also the permanent boiler pilot light.
So, the idea was, taking into account the extra inefficiency of my old boiler, what would come out cheapest.
Well, based on the above. Using the immersion would cost me (rounded up) £2.98 to leave the immersion on all day,
The Gas boiler using 25kwh per day (including losses) comes out at £2.76.
Close!
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