Economy 7, hot water cylinder, on/off?

retiredin2011

will depend how well your tank is insulated, and how much heat is retained from previous day

I heat my water with gas the heater is on 24hrs, there is no time switch.

It uses 2kWh of gas a day if I don't use any hot water.

matelodave

A hot tank will lose more heat than a cooler tank so the ideal situation is to heat just as much as you need/use. Ideally you need a decently insulated tank, so go and buy another jacket and put it over it - that will keep the heat in.


Install a timer so you can turn it on during the cheaper period, ideally for 1-2 hours before you get up in the mornings.
Have your showers and baths in the mornings rather than at night so you don't need to boost your tank in the afternoon or evening.
If you get your timings right your water should remain hot enough during the day and it will still be warm enough to wash up and even have a shower in the evening.
Don't waste hot water by running it down the sink when washing or rinsing.
Take shorter showers, shaving a few minutes in the shower can save a lot of hot water especially power showers or rain-head types. A 10 minute shower at 15litres a minute will use 150 litres (a whole tank full). Reduce it to 5 mins and you'll save 75 litres, fit a flow reducer or economy shower head to 7lpm and you could be down to 35 litres.


We heat for an hour a day, we both shower in the mornings and there's still enough hot water to wash the pots & pans after dinner and we can both get another quick shower out of it before bedtime although the last one is not everso hot.

lstar337

If you are properly wired for E7, then the tanks heater circuit will only be energised during E7 hours anyway.

You shouldn't need to invest in timers, just turn off your boost (daytime) switch in the kitchen and leave the other one on. That will make your tank heat in E7 hours only. IF, the hot water doesn't last, use the boost switch as it is intended - to boost in the evening.

Also, invest in a tank jacket and/or insulate your tank as much as possible.

Cardew

lstar337 wrote: »

If you are properly wired for E7, then the tanks heater circuit will only be energised during E7 hours anyway.

I would question the term 'properly wired for E7'.


I accept that often Night Storage Heaters and immersion heater are often on a separate circuit that is only 'live' during the 7 hours.


However there are variations of wiring for immersion heaters. Commonly these days all electricity consumed in the house is at cheap rate for 7 hours; hence the correct advice to run appliances on a timer overnight.


Some properties are wired so only storage heaters and immersion are on cheap rate for 7 hours. Electricity consumed by lights and sockets is charged at peak rate 24/7.


My house built 25 years ago(with Gas CH) was, and is, fitted with an E7 two rate meter such that all electricity is at cheap rate for 7 hours. There is a 'live' electricity supply 24/7 fed via an on/off switch and timer to the single immersion heater element.


Obviously I normally heat the hot water tank with gas. Although with an old inefficient gas boiler with a 'flamethrower!!' pilot light and a long pipe run from boiler room to HW tank, it would probably be cheaper to heat hot water using the immersion heater in summer.

lstar337

Cardew wrote: »

I would question the term 'properly wired for E7'.


I accept that often Night Storage Heaters and immersion heater are often on a separate circuit that is only 'live' during the 7 hours.


However there are variations of wiring for immersion heaters. Commonly these days all electricity consumed in the house is at cheap rate for 7 hours; hence the correct advice to run appliances on a timer overnight.

I guess I am used to my old system where there was a separate circuit for E7 devices (NSH, Hot Water) that was only energised during E7, but also all other circuits charged at lower rate during E7 hours. This is what I consider the optimal system, and therefore 'proper' by nature.


Some properties are wired so only storage heaters and immersion are on cheap rate for 7 hours. Electricity consumed by lights and sockets is charged at peak rate 24/7.


My house built 25 years ago(with Gas CH) was, and is, fitted with an E7 two rate meter such that all electricity is at cheap rate for 7 hours. There is a 'live' electricity supply 24/7 fed via an on/off switch and timer to the single immersion heater element.


Obviously I normally heat the hot water tank with gas. Although with an old inefficient gas boiler with a 'flamethrower!!' pilot light and a long pipe run from boiler room to HW tank, it would probably be cheaper to heat hot water using the immersion heater in summer.

OK, very true.

The OP does mention that they have two switches for each heater and for the hot water, this suggests to me that there is an E7 circuit which is only energised during the E7 hours.

I only used the term 'properly wired' as a disclaimer in case my advice was incorrect due to differently wired systems. I see how it could be interpreted erroneously.