economy 7

economypaul

I read in a previous answer that it's cheaper to heat water using an immersion heater on cheap rate (night) electricity. My cheap rate electricity is 6p a kw but gas is only 3p a kw all day long. Using an immersion may be more efficient than a condensing boiler but not twice as much surely.

victor2

It depends what else your gas boiler is heating on the way to heating up the water tank, as well as the efficiency.
Heating the water with the immersion heater means 100% of the electricity used goes into heating the tank. If you have a gravity fed hot water system from your boiler, it will be heating considerably more than just the water in the tank - does the first radiator in the system get hot when the boiler is "just" doing hot water?
It's difficult to do a direct comparison - you can find out what it costs when heating water by gas at a time when the heating is not in use just by monitoring your gas meter. It's a bit more difficult with an immersion heater as you can't tell how many hours it is actually heating the water during an "on" period, even if you know it's KW rating.

Wywth

economypaul wrote: »

I read in a previous answer that it's cheaper to heat water using an immersion heater on cheap rate (night) electricity. My cheap rate electricity is 6p a kw but gas is only 3p a kw all day long. Using an immersion may be more efficient than a condensing boiler but not twice as much surely.

Gas @ 3p per kWh hour?

Really? Where do I sign up?

Btw, your gas boiler is not 100% efficient. Unless it's quite modern, it may typically only be 6o% efficient.
And then you need to factor in the inefficiencies of the water travelling between the boiler and the tank ... and of course the pump that uses electricity.

Richie-from-the-Boro

economypaul wrote: »

I read in a previous answer that it's cheaper to heat water using an immersion heater on cheap rate (night) electricity. My cheap rate electricity is 6p a kw but gas is only 3p a kw all day long. Using an immersion may be more efficient than a condensing boiler but not twice as much surely.

Average 'Clear & Simple' BG price quote as of @ tonight's date is :

Direct Debit

- Standing Charge 24.439
- Unit Rate 4.316

macman

Gas should be a bit cheaper, but the gap will not be great if you are using E7 cheap rate.
But the question should really be, why are you still on E7 if you have gas CH and DHW? You are paying a premium rate for all your non-cheap rate electricity usage. Unless you are using a minimum of around 30% of your units on the cheap rate (which is unlikely without storage heaters), it probably won't pay.

economypaul

Wywth wrote: »

Gas @ 3p per kWh hour?

Really? Where do I sign up?

Btw, your gas boiler is not 100% efficient. Unless it's quite modern, it may typically only be 6o% efficient.
And then you need to factor in the inefficiencies of the water travelling between the boiler and the tank ... and of course the pump that uses electricity.

Yes, 3.32p gas and 5.637p per kw night rate electricity. Signed-up in September with Scottish Power, fixed until January 2014. The Vaillant condensing boiler is only 3 years old; how efficient is that?

economypaul

Yes, 3.32p gas and 5.637p per kw night rate electricity. Signed-up in September with Scottish Power, fixed until January 2014. The Vaillant condensing boiler is only 3 years old; how efficient is that?

economypaul

macman wrote: »

Gas should be a bit cheaper, but the gap will not be great if you are using E7 cheap rate.
But the question should really be, why are you still on E7 if you have gas CH and DHW? You are paying a premium rate for all your non-cheap rate electricity usage. Unless you are using a minimum of around 30% of your units on the cheap rate (which is unlikely without storage heaters), it probably won't pay.

You are right; I can't justify economy 7 but I'm stuck with the meter and don't want to pay £60 to change it. My previous supplier EON let me use a single rate tariff by adding the 2 counters together but Scottish Power won't let me do that. That's why I want to increase my night useage by using the immersion heater, I'm just not convinced cheap rate electric at 5.637p per kw is better value than gas at 3.32p kw Signed-up in September with Scottish Power, fixed until January 2014.
What does DHW stand for?
The Vaillant condensing boiler is only 3 years old; how efficient is that?

victor2

economypaul wrote: »

You are right; I can't justify economy 7 but I'm stuck with the meter and don't want to pay £60 to change it. My previous supplier EON let me use a single rate tariff by adding the 2 counters together but Scottish Power won't let me do that. That's why I want to increase my night useage by using the immersion heater, I'm just not convinced cheap rate electric at 5.637p per kw is better value than gas at 3.32p kw Signed-up in September with Scottish Power, fixed until January 2014.
What does DHW stand for?
The Vaillant condensing boiler is only 3 years old; how efficient is that?

If it ever gets warmer so you haven't got your central heating on, you can read your electricity meter at night and then in the morning and see how much was used. Do it for say, a week, with the immersion heater on, then a week with the immersion off. During that second week, use gas for your DHW (=Domestic Hot Water BTW;)) and also read your gas meter. Subtract the average electricity used without immersion from the average used with, and you'll get an idea how much the immersion uses. Convert your average gas usage to kWh and you'll get an idea what that uses. Then compare the cost. Nothing to it really!

macman

It's certainly worth it if you can save the cost of the meter change by switching away from E7.

Pincher

Alternatively, do nothing and switch to a supplier that will add the day and night rates together next time.

Every ten years or so, they have to replace your meter.
Try insisting on a single rate meter when they ring up to make an appointment.

I am with Scottish Power, Fixed Online to Jan 2014 (31 Dec 2013, really), single rate.

Electricity
Primary 18.249p + VAT = 19.16145p
Tier 2 9.226p + VAT = 9.6873p

Gas
Primary 7.099 + VAT = 7.45395p
Tier 2 3.156 + VAT = 3.3138p

So if you paid the £60, this is probably what you could be on.