@derek-m

Have been trialling removing the 5-7am hot water setting since Thursday last week now. Interestingly it has made no difference to kWh used. Usually I'd come downstairs and the smart meter would say by 8am that 0.689-0.700kWh (~50p) had been used, which I've always considered would be mainly from the ASHP heating the hot water from 5am - 7am. However, since deleting that schedule, every morning since, the smart meter still displays pretty much the same kWh / £. Was fairly surprised by this.

Morning @dan-t your .7kWh I hope wouldn’t be 50p. Else your cost per kWh would be 71p. Which is high. 
I wonder if this .7 is your ASHP just on standby. Like mine. If everything else is switched off

Hi Dan,

The fact that it makes no difference to the amount of energy consumed would indicate that the water in the tank is remaining hot overnight, and the heating cycle from 5am to 7am is actually not required. The heat loss on a well insulated tank and pipework should be quite low, so if no hot water is used, the system may top up the temperature once or twice a day.

The major factor that determines how much energy is used, is how much hot water is being used. If taking a shower uses say 10 litres of hot water, then 10 litres of cold water will go into the tank and will need to be heated up to the desired temperature. At this time of year the cold water will probably be warmer than during the Winter, so will require less energy to bring it up to temperature.

The other factor to consider is the deadband on your tank heating system. The deadband is the difference between the temperature at which the heating is switched on and the temperature at which it switches off. It you have a deadband of say 5C and the desired temperature is 50C, then the heating will switch on when the water temperature falls to 45C and then switch off when the temperature reaches 50C.

The energy use shown on your smart meter is probably due to your 'base load', which is the energy used throughout the day by equipment that is left plugged in, things like your refrigerator, freezer, router etc. The cost displayed also includes the standing daily charge, which is added to the bill just after midnight each day.

The reason that I suggested the test was to discover if you needed any water heating overnight, since this is the period when your ASHP would be least efficient in the colder weather. Also, if you are considering some form of solar heating, then it would be pointless heating your water overnight, so that the solar energy is then not required.

I hope this answer your questions but please feel free to ask more if you wish.

@derek-m, a question for you which isn't directly ASHP related. I understand the basics of a non combi boiler HW cylinder but there is one thing I've never quite got my head around. When I turn my hot tap on and the HW gushes out (and it does) I assume it's replaced at the same rate from the cold main.  If I use half a tankful I'll then have in the tank 125 litres at 50 degrees and 125 litres at 15 degrees (or whatever the mains is).  Am I then left with a full tank of lukewarm water until it heats up again?  I can't think of any way this won't happen but then again I never noticed it doing that before with previous non-combi gas boilers.    

Hi Kev,

There will be mixing of the hot and cold water in the tank and some stratification. Obviously, the more hot water you take out, the more cold water goes in. We have cold water tanks in the loft which feed the hot water tank, so this time of year the cold water is not that cold.

If you heat the water to 60C rather than 50C, then you would likely use less, and hence need to replace less, so the mixed temperature would be higher.

I hope this answers your questions.

Hi Kev,

Now that we have returned from the pleasure of food shopping I will add a little extra.

You will no doubt find that the hot water take off from the tank is at the top or near the top. The cold water feed will be near the bottom of the tank. The amount of mixing and temperature equalisation that occurs will be affected by the rate of flow. The faster that you take hot water out of the tank, the faster the cold water will flow in, which will cause greater turbulence and greater mixing.

Just an update on our electricity consumption.

It is now just over a month since the Grant engineer checked out our system.

May was cold and our total consumption (I only have a meter for the whole house) averaged 27kWh per day.

June is proving much better so far with a daily average of 18kWh. None of this will be for heating given the warm weather.

I've booked an electrician to install a separate meter for the ASHP. Once this is in I'll be able to split out the power consumption for the ASHP from all other uses in the house. Total kWh YTD is still worse than last year but is distorted by the awful January figures. The rolling  12 month figures are on a downward trend. Every month this year has been better than the same month last year. When January 2020 drops out (assuming there is no repeat) the 12 month numbers will show a dramatic improvement.

@mike-patrick, good to know you're making some progress. 

Our May consumption was about 30kWh/day, of which 16 was the ASHP.  April (which was much colder) was 41/28 total/ASHP.  June so far is about 13/4; the 4 is nearly all HW as the heating has not been on much.  

Although there are only the two of us we keep the house quite warm.  I'm not quite sure where the 13 kWh per day non-ASHP goes, although I suspect a lot of it is the washing machine/tumble dryer/steam iron but that's not something I would dare interfere in.

Hi Mike,

I find it quite surprising how much electricity you are still using at this time of year.

What equipment do you have connected? Are you using a large quantity of hot water?

Did you ever fully resolve your leak?

Electric/kWh usage is useful, but what’s the cost?  We use £10/w or £60 for that last month of electric. We are an electric house, including cooking, washing, dishwasher and EV. Ok I think. 
So 30kWh per day doesn’t sound bad

Julian,

I thought the objective was to collectively reduce our carbon footprint as well as costs. Maybe we are fortunate in that our home is not large, we have a solar PV system, and a recently installed A2A ASHP. Over the past 7 days up to and including yesterday, we imported 18.4 kWh of electrical energy which averaged 2.63 kWh per day. During the same period our solar PV system generated 130.8 kWh of which 51.8 kWh was diverted to produce hot water and 48.7 kWh was exported back to the grid. Household use during this period was 48.7 kWh, some of which was to drive the ASHP for cooling.

We don't do anything special, we have quite a few drinks throughout the day, though only fill the kettle with the required amount of water. We try to use the washing machine when we have a good generation day and don't have a tumble drier preferring to use the washing line.

We have a fairly modern electric cooker with an inductive hob, and also a slow cooker and crockpot, both of which can better use available solar energy.

We don't have a hectic lifestyle so can think about our use of energy and try to keep it to a minimum.

Quite surpised seeing some high figures, considering the time of year.

Our average usage / cost for May worked out to be: an average of 6.9kWh per day, at £1.14 per day

So far for June our average usage / cost : 5.620kWh / £0.82 per day

And on average for June we are generating 9kWh per day via our solar panels 

We do try to put the appliances on when we're generating solar, but can't always be done.

To put it into context, I can't remember who it was who was using 30kWh per day, but that was our average daily kWh used in January.