UKH

I've just bought a flat which has a hot water tank an immersion heater to provide hot water. This would be fine if the heating was by storage heater - but it's not; the heating is electric radiators and there's an electric shower (no bath), and so the only thing that I actually need hot water for is doing the dishes. I'm currently on an Economy7 tariff but  I'm almost certainly going to move away from that as the immersion is the only thing that makes use of it.

It seems a pointless waste to heat up a big cylinder of hot water every night just to be able to do the dishes, but for most of the past decade I've not had easy access to hot water on demand out of the tap, and so I'm reluctant at the moment to make the solution "switch the immersion off an boil the kettle to do the dishes" as I'm still enjoying the novelty.

Long term, are there any better solutions to having functional hot water without such a waste of energy?

If you have enough dishes, buy a dishwasher and just use it once it's full? You can pick them up second hand normally through local facebook groups 

I don't really have anywhere to put a dishwasher unfortunately, and I don't really produce much in the way of dishes as it's only me in the flat (he says, ignoring the three day collection of dirty dishes on the bench in the background).

If you only want to wash dishes, a tankless under sink water heater will be way more efficient, and a small one can be picked up dead cheap from the likes of Toolstation, etc.

Boiling water tap. Seems like a no brainer. Not mega cheap, but way more efficient for what you're doing.

This could be the winning solution - less bench clutter too if the kettle goes, and in the fullness of time I'll gain a cupboard if the hot water tank comes out.

I'm in a similar position to you, although I have a back boiler for heating and water so have hot water if the heating is on. It takes so long for the hot to come through the tap that I still mostly wash in cold water even in winter, I've been here for about 20 years so I'm used to it. Using branded washing up liquid makes a big difference. If you suffer from cold hands then washing up gloves are nice.

I have had lodgers quite a lot over the years and they often struggle with no hot water (taking a sponge to a pan full of cold grease for example) but I've never found it an issue. Wash as you go, utilise hot cooking water or the dregs from making a brew and wash pans when they're hot, I very rarely have to boil the kettle for washing up. 

You can get micro dishwashers that sit on the work top, that might be an option. 

I suppose I'm similar to you in that I've lived with no hot water, by design or by accident, for much of my independent life. I rented a flat where the immersion went unserviceable quite quickly and it ended up staying like that until we moved out through a farcical ongoing saga of missing electricians and what have you. Then I've since lived on two boats where hot water was either from an instant gas hot water heater (unbelievable how much gas they use), or on the second one from running the engine only. Ergo most things that required hot water were done when the engine had to be running for other reasons.

My problem is that I'm not very good at doing the dishes as I go, and invariably will end up with a multi-day collection of dishes fairly regularly no matter how hard I try.

I suppose there was less onus on 'energy responsibility' until relatively recently, but it does amaze me that the previous owners were happy with having an immersion heater when the only purpose for it is to supply the hot water taps.

Electric shower or power shower? I'm sure you've checked but as you say, odd to have a cylinder and no real use for the HW.

Electric shower (Mira Sport).

Some immersion heaters have two heating elements, one near the bottom and one near the top and you can just use the top one while the water below doesn’t get hot. I suppose you’ve checked for this.

On the other hand, if you’re heating is electric, you don’t have a cheaper way to warm the flat and you don’t in principle waste any heat. If it’s a modern tank it will be very well insulated and the thermostat will only switch on when the temperature drops below the set temperature. If the tank isn’t well insulated, as the tank cools down it just becomes a radiator, though perhaps doesn’t heat the area of the flat where you want the heat.

At the risk of telling granny how to suck eggs, have you checked what temperature the thermostat is set? Before you turn that down do check the required minimum for protection against legionella bacteria. 

I have this, but the immersion timer that's installed, currently, will use the bottom element for overnight heating and the top element for 'boost'. I'm currently (probably not for much longer) on an Eonomy7 tariff, so it makes sense to leave that as-is for now.

Of course I hadn't considered that the heat loss still does something productive in being lost to and heating the flat - basic physics error! And the cupboard doesn't strike me as being all that much warmer than outside of the cupboard, so perhaps the loss and the consumption is minimal. I might actually stick an energy monitor on the circuit and find out what it averages out at. It would be interesting information if nothing else. I'd just automatically assumed it must be quite a large waste for the amount of hot water I use.

It's more the general principle of heating a large tank for little use that I was thinking about - obviously the lower the thermostat the less the excess waste, but it still seems a waste.

I think everyone has missed the obvious solution: do your washing up in the shower; two birds, one stone. 

Paper plates 

Eating vegetarian food makes washing up easier.......a lot less greasy.

Having moved to a new house I'm in exactly the same situation and currently boil the kettle for hot water.

My long term plan is to move to an air source heat pump and wet central heating since electric radiators are much less efficient. This will also provide hot water for washing up. You can get a grant to help cover the cost to do this - https://www.gov.uk/apply-boiler-upgrade-scheme

At the risk of being pedantic you could say all heaters are 100% efficient as energy in equals energy out. I suppose some of the input could emerge as light or sound, but that would be negligible. I think you mean cost effective.

If we define efficieny as paid for energy entering the house divided by useful heat generated then heat pumps are around 300-400% efficient (they take free heat energy from outsideto up theor effiency) and gas boilers are ballpark 90% efficient (heat is lost from them via their exhaust gases). Your statement is only true for pure electric heaters.

Also, sound and noise ultimately become heat. Both light and noise disappear as their waves bounce off solid surfaces, and to a much less extent gases, and vibrates the molecules in these which then becomes heat. Therefore, an electric heater that is very noisy or has loads of lights on it, will still be 100% efficient 

Fair comment. Hadn’t considered heat pumps.

But don't you need more heating as you are all thin and anaemic

:  )

If it's a modern hot water tank, you should be able to find out how much heat it dissipates from the installation manual.  My 5-year-old, 130 litre tank is rated at 70W.  Obviously there are some assumptions involved, regarding water temperature and air temperature, but that should give you some idea.

Cheers

Al

Given the embedded carbon of any replacement you might get, and the fact that for six months of the year the lost heat is actually useful, then it's pretty likely that the greenest thing you can do is nothing (apart from upping the insulation as far as reasonably practical).

Unless you want to rip the whole lot out and go heat pump, but that's a pretty big deal.

Of course as paid for energy we should probably include cost of apparatus, installation, maintenance, replacement time, heat uselessly lost during transmission, cost of insulation.

Put it in the place where your plate cupboard is - that's all it is, a dirty plate cupboard .

A very good point well made, and of course as we as a country move further towards sustainable generation, it becomes even less of a concern moving forwards in the long run.

That's a different calculation from the efficiency calc and much more dependent on circumstances.

From an environmental standpoint it will almost always work out "cheaper" in the long run, unless the house burns down or gets demolished. 

If you plan on owning long term and you have the capital to invest, it will work out cheaper in the long run, although it may not beat another investment you could have made.

If you don't plan on owning long term, it probably won't add enough to the house price to result in profit, unless global instability/regulations make it so.

So the main reasons to install are probably comfort and for the sake of the children, rather than financial, leaving it as a "good thing to do" for those who can afford it rather than the sound financial choice for everyone that it needs to become.

Not sure how effective a solution this would be. I have a tankless under sink hot water heater (5.5kW) in our en-suite (due to the layout of the house it's a long way to run a hot water feed from the combi boiler).

Great for hand washing, but it'd take a fair while to run a bowl of very hot water for the dishes. Plus you need a separate electrical feed installing (25A RCD on ours).

A better option (if space permits) would be a small tanked system (10 - 15 litre ish). If space is tight unvented heaters don't need an expansion tank, but need a pressure relief tap (which drips into the sink to relieve pressure build up). These usually just need a fused spur off the ring main, rather than a separate feed from the consumer unit.

No. They cost an arm and a leg. The OP doesn't need to keep a tank of constantly boiling water under the sink. They need a little bit of hot water which a point of use electric tap would provide much more economically

Overall they'll be more economical (installed cost much lower) but as far as I can see from the numbers, they're actually very well insulated and don't really lose much throughout the day so there's not a lot in it from an energy use perspective.

So really it would be more down to flowrate of the hot/boiling water, whether you can run mixed water at a sensible temperature out the boiling water tap and whether or not you might want to save the space of a kettle.

But yeah, cost wise a point of use water heater may be a better shout - I haven't installed either but have used boiling water taps at families - if you do go for one, make sure it's got a user friendly interface as some are a pain in the ass!

You're right that flow rate could be a concern with a POU tap. With boiling water taps I think a hot water connection is still needed (but it's a couple of years since I read up on them). If there are taps that can mix the boiling water with cold water to provide hot water, I imagine the tank would empty quickly as they tend to be sized for filling cups.

Fair point!