high electricity bill - is it because my timer settings?

[glider26]

Hi,

We are a couple living in a rented 3 bed house with a boiler and tank equipped with an immersion heater, both located in the loft. My elec bill for the 6 weeks to Oct 9th is quite high (£121 for 970 units) and I suspect it's because of the way I set the immersion heater.

We have a thermostat in downstairs and a timer (one for CH, one for DHW) in the old airing cupboard. Also in this cupboard are two switches, one for the boiler and one for the immersion heater. The CH timer has it come on twice a day, 2 hours in the morning and 5 hours at night (assuming the thermostat is tripped by a low temp). So far so good. The DHW at the moment though is only on for about 20 minutes per day, just before we wake up. We take a shower each/day on average, and sometimes less than that (because we shower at the gym, not because we're filthy ).

I'm not familiar with the immersion heater logic. Does it come on to maintain a certain temp in the tank? In which case should we have the DHW timer stay on longer so as to use gas instead of elec? How long for?And does the tank get topped up with cold mains water as it is depleted by DHW demand?

Thanks for any help.

 

[big-all]

if you have gas central heating your immersion should be switched off

if not you need to find out if your on economy 7 or other off peak supply

the hot water stays layerd the cold is fed in the bottom and dosnt mix much so if you use half a tank off hot you dont finnish up with a full tank of luke warm water you finnish up with roughly 1/2 a tank off hot warm then cold with only the middle few inches mixing

 

[Diyisfun]

As above, the immersion heater is there as an emergency back up.

 

[JohnD]

if your immersion heater, and the pipes around it, are very well insulated, it should not cost that much, unless the thermostat is faulty and it is overheating or running continually. In this case you would notice the water is uncomfortably hot. Or unless you have a leak or a running or dripping hot tap or pipe. An immersion heater uses about 3kWh per hour at about 10p each, say 30p per hour when running. Look at the insulation , and test the water temp with a thermometer, and tell us what you find

however, as Al says, if you have a gas boiler, let that heat the hot water as well. Gas costs less than half the price of electricity.

If you have other electrically-heated appliances, such as fan heater, tumble drier, dishwasher, washine machine, these all use about the same 3kW when the heater is running.

 

[kevplumb]

switch the immersion heater off

 

[glider26]

Thanks, I've switched the immersion heater off and increased the time during which the boiler heats up DHW to 1h/day. I'll increase it if I get complaints...

 

[JohnD]

it's still worth checking the insulation and the water temperature

A modern boiler will heat a modern cylinder in about 20 minutes and it will stay fairly hot for 24 hours if properly insulated.