We'd like to remind Forumites to please avoid political debate on the Forum... Read More »
📨 Have you signed up to the Forum's new Email Digest yet? Get a selection of trending threads sent straight to your inbox daily, weekly or monthly!
Most efficient timing on an immersion only hot water tank using Economy 7

fishpasteuk
Posts: 1 Newbie
in Energy
I am renting a property that has a heat source pump for the heating and an immersion heater for the hot water, with an electricity only tariff on Economy 7.
I'm looking for advice on how to set the most efficient setting for the immersion heater, bearing in mind that I am able to control it to within half hour increments throughout the full 24 hours. I cannot change anything about the system at all, just the thermostat setting.
I had been having it running for a total of three hours a day - two from 4am to 6am and one at 5pm,but sometimes, because of the ambient temperature that's not enough and we end up with lukewarm showers especially at the end of the day.
I'm now trying four and a half hours running from 2am to 6:30am, which seems to work well.
Ideally I'm looking for general advice and, or, people's experiences with similar electricity only setups.
We don't have a smart meter and don't want one (until all the reported problems have been ironed out.)
Many thanks.
I'm looking for advice on how to set the most efficient setting for the immersion heater, bearing in mind that I am able to control it to within half hour increments throughout the full 24 hours. I cannot change anything about the system at all, just the thermostat setting.
I had been having it running for a total of three hours a day - two from 4am to 6am and one at 5pm,but sometimes, because of the ambient temperature that's not enough and we end up with lukewarm showers especially at the end of the day.
I'm now trying four and a half hours running from 2am to 6:30am, which seems to work well.
Ideally I'm looking for general advice and, or, people's experiences with similar electricity only setups.
We don't have a smart meter and don't want one (until all the reported problems have been ironed out.)
Many thanks.
0
Comments
-
Hi,
you've got the right idea running immerser in morning whilst still on the cheap rate.
You should have a boost option on timer for a quick boost at night, if needed, though this will be on day rate.
Have you checked the insulation on your water tank, a well insulated tank should keep water warm most of the day, maybe it is needing a bit more insulation.0 -
You are about right although you shouldn't really need the afternoon boost if the tank is properly insulated and you are reasonably frugal with your hot water consumption.
Try using less hot water by having shorter showers or fewer of them. Learn to shower in 5 minutes or less. Dont let hot water run down the sink when washing yourself or the dishes. You dont need hot water to rinse stuff or wash your hands - every time you draw off hot water you leave the same amound sitting in the pipework to get cold.
Fit flow reducers to the taps and the shower to decrease the volume of water that comes out and as said above make sure the tank is well insulated.
We heat our hot water with a heatpump and it's heating the tank for less than two hours a day. We've got all the hot water we need including enough for showers the next day if we get up before the heat pump kicks in.Never under estimate the power of stupid people in large numbers0 -
If possible you just need to check what your E7 hours are with your supplier. Mine are 11.30 pm to 1.30 am and 3.30 am to 8.30 am in the summer time and one hour back in winter but it varies from area to area.
My tank only needs about two hours to heat up but I have the thermostat set quite high so I just need a 30 min boast later in the day.
If you are able to do so look at your thermostat setting.
https://www.diydata.com/problem/immersion/immersion_adjustment.php0 -
If your tank is well insulated, the heat losses are very low. Typically between 1kWh and 2kWh over 24 hours for a full tank of hot water at 65C. This is measured by a British Standard and the figure is usually stamped on the cylinder. As an example my large 180litre tank loses 1.3kWh with the above criteria.
In practice few people have their hot water at 65C for 24 hours so losses are much lower.
My point is it is not critical that your tank is only heated in the last couple of hours. It is also pertinent that any heat lost warms the fabric of the house so is not wasted for much of the year; that is why many HW tanks are in an airing cupboard.
So heat produced at off-peak rates warms the property during the day!0 -
Is your E7 teleswitched, or by a clock on the meter? Check the latter by looking at the timer, or call your local DNO if teleswitched, They will give you the timings.No free lunch, and no free laptop0
This discussion has been closed.
Confirm your email address to Create Threads and Reply

Categories
- All Categories
- 351.4K Banking & Borrowing
- 253.3K Reduce Debt & Boost Income
- 453.8K Spending & Discounts
- 244.4K Work, Benefits & Business
- 599.6K Mortgages, Homes & Bills
- 177.1K Life & Family
- 257.9K Travel & Transport
- 1.5M Hobbies & Leisure
- 16.2K Discuss & Feedback
- 37.6K Read-Only Boards