High energy consumption on E7...

Glum

Kilty wrote: »

I live in a small 2.5 bedroom detached house with night storage heaters and economy 7 and seem to be using a large amount of electricity yet I only use 1 of the 3 storage heaters (which is probably as old as the house, around 20 years) and the immersion heater (which is only about 4 years old and the timer for it about 2 weeks old) overnight.

Day use is fairly stable and normal (I've used an energy monitor to measure it) but when I connect the monitor to the circuit for the storage heaters it measures about 4kW for the entire 7 hours, which would suggest the storage heater and immersion heater are operating at their maximum 2kW each all night when they're turned on which equates to 28 kWh for just one storage heater and the hot water heating plus any use on the other circuit (washing machine, dishwasher) :eek:. 28kWH per night (10220 per year) is more than the average "high" user uses aparrently....

Is this normal? Do I just need to live with it or is the storage heater faulty (should it be turning the heating element off once it reaches a certain temperature?) and can I limit the number of hours the immersion heater is on without impacting upon the availability of hot water too much?

Hi Kilty

It sounds to me like the thermostat is indeed stuck in the closed position. I would suggest turning the heater off at the wall for one night to check that the meter reading is reduced by the appropriate amount. Assuming nothing else has changed, the difference should be obvious. If the thermostat is broken, I would expect the heater to be very hot in the morning, even if the output flap is open all night or the input is set to min or 1.

Storage heaters are almost useless unless you leave the output flap set to min, otherwise they start giving off heat as soon as they turn on and there is nothing left for the following evening. The manufacturers advise users to try and predict what the weather is going to be like for the following few days but I doubt if many people bother, so the flap is just left fully open.

If you have a digital meter you might be able to see when the tariff changes since the display flashes on and off when the rate is active. The actual start and stop times vary depending on which region you are in (where we live it’s between 00.30 and 0730) so check with your supplier.

By the way, don’t attempt amateur repairs on the unit, but it is possible that the thermostat might be replaceable without condemning the whole heater. Consult a qualified person, or an electrician.

If your immersion heater thermostat is set quite high, you should be able to heat a typical tank-full in a couple of hours. So the "on" period need not be that long. You could set it to come on say two hours before the end of your off-peak period and then see if you need to start a bit earlier if the bottom of the cylinder is still cool in the morning. Remember that good tank insulation might mean that the power is only needed for a couple of hours at say 1 am and then it stays hot until morning. However, it would be daft to keep it topped up all night when you don't need the hot water since you are just losing heat into the airing cupboard. You don't get something for nothing with electrical heating unless you control the losses and the wastage. One example is that low-energy light bulbs run cooler so you have to turn up the room heating to compensate for the reduction in heat from incandescent bulbs; it may be a tiny amount, but it is still a measurable factor.

Hope that helps a bit.