Cheapest way to use the immersion heater

roxalana

Just bumping this up!

Any help appreciated!

SnakeDoctor_2

I'm no expert, but what I would do is:-

1.Sort out the insulation on the hot water tank - double the recommended amount.
2. Confirm with your suppliers exactly what your economy 7 hours are.
3. Set the immersion timer to be on from about 03:00 to 15 minutes before the economy 7 time ends.
4. Consider changing your big hot water usage times from the evening to early mornings.
5. Only manually switch the immersion on if and when you need more hot water.
6. Check that you are on the best tariff for your area and usage pattern; and check again on a yearly basis.

I'm sure some of the experts will correct me if I'm wrong or there is more that you can do.

Cardew

Agree with above, have immersion on during the off peak times(don't forget that the clocks going forward can affect timings). A well insulated tank will lose very little heat even in 24 hours.

Under no circumstances have it on 24/7, you will lose all the advantage of an Economy 7 tariff.

grahamc2003

roxalana wrote: »

Hi,

I'm having problems applying this thread to my circumstances:

I have economy 7.

I have no gas supply.

I have storage heaters.

I live in a medium sized 2 bed flat.

I've never had an immersion heater before (I've always had the instant hot water kind). It has a timer. I am typically out of the house 7am-7pm but my husband works shifts. We want hot water for (usually evening) baths and washing up. I think the shower may heat itself but not sure.

Firstly, the insulation on the tank is woeful and I will rectify this.

In my circumstances, am I best to a) have it on 24/7 - if so, where will i find the setting that cuts it off when it reaches a certain temp b) heat it for a few hours offpeak (3.30am-8.30am) - if so, how long for and will it still be hot enough in the evening for a bath? or c) set the timer for when I actually want to use it and leave it cold the rest of the time?

I don't think it is the dual kind - how would I know? I only have one timer. Where would I need to look to know for sure?

Thanks!

Option a) No!

b) My e7 hours end at 07:30 today (08:30 from tomorrow) local time. You could heat a whole tank of water at a cheap rate by setting the immersion to come on for an hour or so ending when your e7 period ends (07:30 or 08:30). No point in starting to heat it at 03:30 imv, you'll just lose lots of heat from say 03:45 for no benefit. In any case, with a poorly lagged tank, you'll lose lots of heat from early in the morning till the water is used in the evening.

c) Depending on how much heat you lose in b), it may be better just to switch the heater on at peak rates for 45 mins or whatever and then use it straight away, with minimal heat loss.

No one can say whether b) or c) is better in your situation, it depends on your insulation, day and night rates, times of your hotwater usage etc.

If for exmple, your day rate is 10p and night rate is 5p, it would make no difference what you did if you lost exactly half the heat you'd put in at cheap rates before you used it. If you lost more than half, then c) is better, if you lost less, then b) is better.

Usually, e7 users have very well lagged tanks, and have low losses, so b) is usually better for them.

I'd just spend a tenner on a purpose build insulating jacket, or get someone to fit one for £50, and use cheap night rates.

Richie-from-the-Boro

roxalana wrote: »

Hi,

I'm having problems applying this thread to my circumstances:

I have economy 7.

I have no gas supply.

I have storage heaters.

I live in a medium sized 2 bed flat.

I've never had an immersion heater before (I've always had the instant hot water kind). It has a timer. I am typically out of the house 7am-7pm but my husband works shifts. We want hot water for (usually evening) baths and washing up. I think the shower may heat itself but not sure.

Firstly, the insulation on the tank is woeful and I will rectify this.

In my circumstances, am I best to a) have it on 24/7 - if so, where will i find the setting that cuts it off when it reaches a certain temp b) heat it for a few hours offpeak (3.30am-8.30am) - if so, how long for and will it still be hot enough in the evening for a bath? or c) set the timer for when I actually want to use it and leave it cold the rest of the time?

I don't think it is the dual kind - how would I know? I only have one timer. Where would I need to look to know for sure?

Thanks!

The hot water cylinder should be Part L of the Building Regulations spec :

- two thermostatic immersion elements [ one day boost & expensive & one night normal & cheap ] connections
- - the top immersion, which is always on a timer, heats only the small amount water above it and is the expensive daytime boost
- - the bottom immersion heats all the water to the top of the tank and is night-time cheap
- and extra thick factory applied insulation giving improved performance on heat loss
- - typically a minimum of 60mm thick, as opposed to the 30mm jacket on a standard cylinder

My general take is that :

- night leccy costs are 25% of day leccy costs
- the bigger the tank the better
- the clock [ is set correctly ] will auto adjust for summer - winter time
- if you need an extra water heating boost you have a conventional day time cost switch for that purpose already
- switch the E7 water on when you move into the property and leave it alone [ other than extended holidays away from your house ] until you sell the property
- its false economy to switch it on and off

On a different subject :

- water and heat costs on E7, a single / couple out at work all day will use their kWh 60% day 40% night
- a retired couple will be closer to 50 50%

Any questions please ask:D

Cardew

Richie-from-the-Boro wrote: »

- night leccy costs are 25% of day leccy costs
- the bigger the tank the better
- the clock [ is set correctly ] will auto adjust for summer - winter time
- if you need an extra water heating boost you have a conventional day time cost switch for that purpose already
- switch the E7 water on when you move into the property and leave it alone [ other than extended holidays away from your house ] until you sell the property
- its false economy to switch it on and off

1. Most cheap rate electricity is around 5p/kWh and the rest is normally 12p-13p/kWh(excluding tier 1)

2. Not all clocks auto-adjust - many switch mechanically - mine for example and Graham's above:

My e7 hours end at 07:30 today (08:30 from tomorrow) local time

3. You are making the assumption that immersion heaters are always wired on an E7 circuit that only switches on for the 7 hours.(like yours?) Many are not!

My house, and many others, have everything in the house on cheap rate and everything on day rate for the other 17 hours. My cylinder only has the one immersion heater element. So leaving it on all the time as you suggest would mean it operating on both cheap and day rates.

The fact that Roxalana has a timer for the immersion heater(like myself) suggests that her immersion heater is similarly wired.

roxalana

Thanks everyone.

Have bought a second tank cover today & am then also going to store our spare duvet around it too!

Rates are:

Tier 1 Day = 24p per kwh
Tier 2 Day = 9p per kwh

Night rate = 4p per kwh

Night = 11.30pm - 1.30am and then 3.30am-8.30am

I think I'll try setting the timer for the latter end of the offpeak and see if it lasts til the evening on days we have baths, but I think otherwise I'll boil the kettle for washing up and try and compare how much leccy the shower uses as well.

HappyMJ

roxalana wrote: »

Thanks everyone.

Have bought a second tank cover today & am then also going to store our spare duvet around it too!

Rates are:

Tier 1 Day = 24p per kwh
Tier 2 Day = 9p per kwh

Night rate = 4p per kwh

Night = 11.30pm - 1.30am and then 3.30am-8.30am

I think I'll try setting the timer for the latter end of the offpeak and see if it lasts til the evening on days we have baths, but I think otherwise I'll boil the kettle for washing up and try and compare how much leccy the shower uses as well.

Buying the tank jacket will only save you a few pennies per week.

The loss rate of a tank that had been claimed earlier is about 100W per hour. That is costing you 0.4p per hour or £35 per year. This can be reduced by 10-20% by extra lagging ....but by lagging the tank a bit more you need to replace the heat that was lost into the room by extra heating in the house by turning the storage heating up or by using electric heating a little bit more in the evening as that is charged at 9p per unit that will cost you an extra 0.9p per hour during the 6 month heating season. The net gain/loss over the year is nearly zero.

grahamc2003

HappyMJ wrote: »

Buying the tank jacket will only save you a few pennies per week.

The loss rate of a tank that had been claimed earlier is about 100W per hour. That is costing you 0.4p per hour or £35 per year. This can be reduced by 10-20% by extra lagging ....but by lagging the tank a bit more you need to replace the heat that was lost into the room by extra heating in the house by turning the storage heating up or by using electric heating a little bit more in the evening as that is charged at 9p per unit that will cost you an extra 0.9p per hour during the 6 month heating season. The net gain/loss over the year is nearly zero.

100w per hour is meaningless. I think you mean the tank loses heat at 100w. While the units are then correct, the value is way out. I'd say you could lose heat from a hot tank at 100w even from a well insulated tank. An un/badly insulated one (like the op is asking) at a high temperature would radiate and convect at something approaching 7/800w I'd estimate (as it cooled down, the heat loss would be less). It's a large area, made from a highly conductive material, and the temperature differential is large, so 100w is way out (for a poorly insulated tank at a high temperature).

Although the heat loss does heat other things, unless you spend your evenings in the airing cupboard, you're unlikely to get much benefit, and since the tank is usually upstairs, it wouldn't heat much downstairs to any degree, so there aren't the savings you say from the rest of the heating system (there may be a small amount to offset under normal circumstances imv)

It's strange that you seem to think there are no savings to be made from one of the most cost effective actions you can take - by insulating the hot water tank!

HappyMJ

grahamc2003 wrote: »

It's strange that you seem to think there are no savings to be made from one of the most cost effective actions you can take - by insulating the hot water tank!

Assumptions have been made. The energy saving trust claim that a householder can save £35 per year by fitting a jacket to an uninsulated tank but the assumptions they use are that the tank is completely without insulation and is heated with electricity and the heat previously lost to the room is replaced by powering up the gas central heating longer for 7 months of the year. Gas is cheaper than peak rate E7 electricity. In the examples on the energysavingtrust's website they use the electric rate for heating the water at 12.5p and the heat replacement effect of the gas is at 3.67p. For a householder on E7 the savings are minimal as they are heating the tank for 4p and heating the room for 9p per unit.