Hot water tank...immersion heater only

[ValentineWiggins]

Hi all

We have a megaflow hot water tank which runs off an immersion heater. It's currenly wired into the mains so that it is running full time...which strikes me as potentially not efficient.

Does anyone know - is it better to warm up the whole tank twice a day, and turn the heater off in the middle, or to keep it all hot all day? I suspect it is going to depend on the rate of heat loss from the tank (as well as hot water usage) - anyone have any other thoughts? Other than to try both and watch the electricity meter!

Cheers

if it is left hot all day, it will waste IIRC about 2kWh of heat a day through the insulation, costing about 28p. Most people use this to warm the airing cupboard. You can save a little by using a timer so that it switches on the immersion heater before you get up in the moring, and before you get home at night, and to go off before you leave or go to bed. However an immersion heater is quite slow to heat such a big cylinder, so the timer will need to be on for quite a long time.

If you have an economy 7 or similar overnight cheap rate, use the timer to completely heat it overnight, and only manually switch it on if you are running out of hot water. A Megaflo with immersion heaters only is usually specified in such a house, often with storage heaters or UFH on the nighttime rate too, which costs about half the daytime rate.

These big cylinders usually have a main heater near to bottom to heat all the water, and a small one near the top to just top it up.
They both have thermostats so they will not draw any more electricity once they are up to temp.

"These big cylinders usually have a main heater near to bottom to heat all the water, and a small one near the top to just top it up.
They both have thermostats so they will not draw any more electricity once they are up to temp. "

Ah ha! That is the answer then...so it's probably not wasting too much money.

You could add a cylinder jacket to reduce heat loss and make it more efficient. Also worth checking what the thermostat is set at many are set at 60,but decreasing to 55 can save you a goodly amount of money.

it's a Megaflo, so pre-insulated to a very high standard in the factory.

We have a well insulated immersion tank that heats up twice a day when our low rate electricity kicks in, we have noticed lower electricity bills since the timer switch wa sfitted.