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Economy 7... getting my head around it

(30 Posts)
sleepyhead Wed 20-Nov-13 20:40:55

We've just bought a flat in a block without gas, so all electric (I'm going to get a quote out of interest for installing a gas supply in the long run, but that's at least a couple of years down the line).

Meter is eco7. Storage heaters and a cylinder for water. I've never used storage heaters before. We used to run up huge bills with an immersion heater before we got gch in our current place.
The flat has excellent insulation and is surrounded by others so heating shouldn't be too much of an issue and I'm wondering is there some calculation you can make to work out whether you're better on a standard electricity tariff without having to do a few months trial and error?
Our lifestyle: 2 children, dh at home with ds2, I'm at work 3 days out of 7 so we're about a lot during the day. Come April dh will return to work and the flat will be empty 8.30-6 3 days a week.

I'm particularly hmm about whether an overnight heat of the water will last anything like long enough for a family of 4 and whether we'll end up heating a lot of it at the expensive rate.

Also confused at having to predict heating requirements a day in advance...

Any advice from eco7 users past & present?

sleepyhead Fri 20-Dec-13 21:30:37

That's good to know. How long should a cylinder that size take to heat up? Just wondering how long I should have it on overnight.

PigletJohn Sat 21-Dec-13 00:56:33

modern cylinders with modern boilers are sized to heat up in about 20 minutes.

However a modern boiler may be as much as 30kW of power, but your immersion heater is only 3kW so could take about 10 times as long. It is also twice the size of a typical cylinder. However, the immersion heater has a thermostat which will turn off the power as soon as it comes up to temp. So it is normal to set the timer to come on at the start of the off-peak period, and let it run until it automatically turns itself off. A well insulated cylinder does not lose much heat per day.

If you have a large cylinder with off-peak supply, you may find it has two immersion heaters, one near the top and one near the bottom. The bottom one is to heat up the entire system off-peak; the top one is normally switched off, but will give you small amount of full-price hot water more quickly, if you run out during the day. an immersion heater usually has a round cap in black plastic or silvery metal sticking out of the top or side of the cylinder, with a heat-proof rubbery white or glossy black flex going nto it. Never take the cap off unless you have isolated the power and know how to test for dead (before you are).

If you ever find the water is scaldingly hot, then the thermostat in the immersion heater may be either adjusted too high, or faulty. Newer ones have an overheat cutout to trip them off before they can boil. It is very easy to change the thermostat in an immersion heater, but to change the element you should look for an experienced plumber, they can get stuck.

cafesociety Sat 21-Dec-13 15:20:29

'Storage heaters are absolutely shit. We've just replaced all ours with normal electric heaters and come off economy 7. Our heating bill has gone down and our house is actually warm now. We only managed one winter with the storage heaters'.

This is what I did too. Bills are absolutely fine [about £250 for the 6 winter months] and the house is warm. Although I do use a woodburner when the weather is very cold.

Someone I know has one storage heater in a studio flat, and I'm in a fair sized 3 bed place [no heating in bedrooms though, don't like it]. Her bills on economy 7 are awful, and more than double mine.

DoctorGilbertson Sat 21-Dec-13 15:33:01

I'm on economy7. No gas to the house. Was on a combi boiler/gas heating before.

Seems OK so far re: bills etc.

our nighttime hot water does two showers in the morning and the kids bath in the evening - we never need to use the daytime circuit.

We have a storage heater (well a kind of hot air thing) - it holds heat well but again I agree Feb will be the test. our bills have gone up a lot since we turned the heating on but also the tumble dryer I guess.

I'm tempted by the scottish power rate that does an expensive first however much electricity followed by cheap after that but waiting for the end of the year to see how much our annual use is.

sleepyhead Sat 21-Dec-13 22:29:29

My main gripe with my, ooh 6 whole days, experience with the storage heaters is that they're too warm so far, although with output down half way that's improved.

I've been taking daily meter readings and our bills at this rate will be about £50 higher than our previous place, BUT that's largely to do with the fact that we're warmer and using more heating. We had our thermostat on the gch set at 18 and the heating was on maybe for 2hrs a day. We'd boost it a bit for sitting around in the evening to maybe 19 or 20. It was also a (large) 1 bed. This is a 3 bed.

With the storage heaters I'd estimate the temperature in the flat at around 21 degrees + all day and night.

I suspect we could easily get away with switching off another storage heater at the moment. Might give that a go.

I've further investigated the hot water cylinder and it does have 2 cables coming out of it each with a wall switch, so presumably one of them is a booster.

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