One of the other changes that we have made recently to our set up changing the 'when' we heat hot water. Rather than heating it 24/7 the engineer changed the setting to heat it when it was called upon. I'd be interested to get some feedback on this?

It certainly seems to have a made a difference in the cost at the moment - however as we're not using heating at the moment, the real difference will only be seen in winter. 

To give you an example, the change was made on the 26th April - most days prior to the change at 8am the Smart meter would say we'd used 90p+ worth of electric - post change we're at a lower 50p by 8am. (These costs are for the recent weeks, not the colder winter months, where we'd regularly come down at 8am to £2+ already).

We are expecting our first baby in October, and I won't lie I am quite worried about the cost of heating the house and hot water once the baby arrives. With just the two of us, in the winter our heating only really comes on in 2 rooms and at specific times of day, heating the house all day and no solar power, I am dreading costs of £15+ per day.

I've pasted in a couple of graphs I've been using to track which show actuals in terms of usage and cost going back to January. May's average is to date, only 3 days worth of data.

Morning Dan T

You are collecting a lot more data than I am. But I think your plan to only heat when needed is sound. Else the ASHP only heats a bit, which is inefficient. 
My h/w is currently heated for free via solar PV and my Solic 200 diverter. I have my ASHP to top up heat. For 4 hrs at night when my Octopus Go tariff is cheapest. The solar just continually heats, where the ASHP is set to re-heat if the Mixergy tank is below 30% to a max of 80%. I’m monitoring to see how effective this is - mainly via my daughter/wife complaining if there is no hot water 😊

@julianc thanks! Yes heating the hot water has been a bit of trial and error for us. Previously it had been set to heat to 50 degrees 24/7. An engineer made some changes to that last week, but twice in the following 5 days we ran out of hot water. 

We now have it heat the hot water tank 3 times a day. 5am-7am, 11am-3:30pm, and 6pm-8pm. I may consider changing the 5am-7am, as that isn't a very efficient time to be heating the tank, but it does mean there is hot water in the tank ready for morning showers.

We are pumping our excess solar into the grid at the moment, tho in hindsight I wish I'd gone for a converter and use the solar to heat the hot water. That said, during winter, there is very little solar so I am not sure it would have a big impact on us anyway.

@dant, our DHW is set to reheat every time we use hot water. There are definite spikes in consumption when we have showers or baths in the evening. I think there is a lot of merit to heating hot water on a schedule, and to my mind it could save money. I think that's an experiment I'll undertake, and in our case it could be more beneficial because we have an iBoost connected to the solar PV system, so the sun should be heating the water during daylight hours.

The only issue with schedules is that if you've used a lot of hot water for whatever reason that day, you may run out of it before the scheduled reheat. 

DanT you definitely need to get a diverter. You look like a “data man”, so perhaps the Solic is not for you, but I can certainly recommend it.

https://www.earthwiseproducts.co.uk/  

It doesn’t provide any app or data, but it’s reliable, beautifully engineered, made in the UK and 10 year warranty. 

Derek made a good point about not heating h/w with ASHP at night because that’s when the air is cold. Hence ASHP less efficient. But I’m paying 5p compared to 14p at night. 

But it’s a good discussion to consider the different options.

There is also the Homely Energy, that offers a service that links the ASHP to the agile energy tariffs. I looked at it, there is a Daikin solution, but decided not to invest this time around. But to see how my Nest, basic TRVs, and Mixergy tank can manage heat from the ASHP as simply as possible. 

So much to consider 😄

@editor cheers Mars. Yeah we noticed we ran out of hot water with just two schedules, I added a third schedule yesterday so we will see how we get on. If we run out of hot water again tho, I think I'll need to reconsider. 

@julianc thanks I will check this out - not sure if this effects me feeding into the grid. I assume I'd still be allowed to get a diverter, maybe I'd just need to tell the energy provider I was getting one. 

During the winter months - when there is no solar, I assume the diverter doesn't really do much? How big is your solar? We have a very small system 2W I think.

Hi Guys,

I am going to have to get my finger out and complete the remaining parts of the article on home energy efficiency 'How to train your Enthalpy'.

As Julian states, dependent upon your electricity tariff, it can be more cost effective to heat your water overnight, but this is probably not the most efficient way. Being a Yorkshireman, who wishes to minimise his carbon footprint, I try to do both.

The main problem in the UK is the inconsistency of our weather, we have on the odd occasion experienced all four seasons in one day. So a setup that works fine one day giving the best efficiency and lowest cost, could be less efficient and more costly the following day. I am therefore continually looking at ways to automate our system to cope with the variations from day to day.

Solar PV is certainly an excellent investment, though as Dan states its usefulness in Winter is limited. Our system (4kW) provides virtually all our hot water needs from Spring through to Autumn, though we don't have a large ASHP demanding lots of electrical energy. It should be remembered that a diverter will only divert the excess output from a Solar PV system, so in Dan's case, fitting a diverter would not be as beneficial, since his Solar PV system is rated at 2kW.

My particular diverter is useful in that it provides data giving, not only details of how much energy is being generated, but also where that energy is being utilised. Please see attached photo's.

A better solution for Dan would probably be Solar Thermal, since it is more efficient than Solar PV, requires less roof space and is cheaper to install, and also his ASHP would not be stealing its output. I do believe that it also qualifies for RHI payments. I don't have a Solar Thermal system, so would welcome feedback from anyone who does have one. The only drawback would be if Dan's hot water cylinder only has a single heating coil rather than a double, in which case he would probably have to also change his tank.

Because water has a high thermal capacity, (it takes 23 times more energy to heat a quantity of water by 1 degree as against air), it is therefore necessary to either have a large cylinder or try to plan your hot water usage, so that not everyone is wanting to take a shower around the same time. In this way it would allow whatever heat source is available to provide hot water.

What I think that you should try initially Dan, is to set the schedule to heat your water throughout the whole of the daylight hours, when your heat pump is at its most efficient. It would therefore provide the hot water during the day when you need it. During the night the temperature of the water will fall slightly, but should not be by too much. since you are not using it. Although it is scheduled on, your ASHP will only be heating the water as you use it and to replenish the losses that occur. Obviously, the more hot water that you use, the greater the heat demand and the greater the expense.

Regards,

Derek.

@derek-m thanks! I've made amendments to when I heat the hot water, trying to utilise the solar energy. I think the challenge is likely always going to be when we're home and using the hot water. i.e. in normal times it's likely that we will be using hot water after 6pm in which depending on the time of year it'll either be dark or more than likely require the ASHP to provide the power. 

I've set it 11am-3:30pm now to heat the hot water, but also again slightly before and after (6pm-8pm) we're likely to use it - whilst this means it won't be as efficient it hopefully will mean we don't run out of hot water when it's needed. I feel its going to be trial and error to fine tune it.

My main concern is the winter months now, with a baby on the way, I dread to think how expensive Oct - March is going to be. We will need to have the heating on a lot more as well as the hot water no doubt. At it's peak, our most expensive day last year was £8, but that was heating just a few hours a day at specific times. It's concerning thinking if the heating is needed on all day what that will look like.

Hi DanT,

Congratulations on the baby, though you do realise that you can't take them back. Also you can't encourage them to leave home, by changing all the locks, until they are 18 years old.

Joking apart, I wish you and your wife all the best.

It may not be as bad as you fear. Think of heating your home like driving your car, getting up to speed requires quite a bit of fuel, but once up to speed your fuel consumption falls quite dramatically, since you are just replacing the losses.

So before Winter you should be looking at ways to reduce the losses, by improved insulation and draught proofing, which is probably the cheapest and most effective way of reducing your bills. Even if you have double or even triple glazing, you could consider something like Stormguard Secondary Glazing Film for use during the Winter months.

Rather than daylight hours, for scheduling your hot water heating, I should have said when the outside temperature is warmest. Hence your ASHP is at its most efficient. Obviously there will be days when this is not possible, but if you look at the weather information, the temperature starts to rise a couple of hours after dawn, peaks around mid afternoon, and then falls gradually towards dawn the next day.

I can't sugar coat it, there will be some expensive days in the Winter, but by minimising your energy requirements throughout the year you will not only help the planet, you will also help your bank balance.

DanT - we have 4kW of solar PV - we generate about 3700kWh per year - as you say much more in the summer.  My system is 9 years old (see detailed description in the Solar PV folder in tis forum).  If your PV is metered to the grid, it will do.  I only have a generation meter.  Only just had my ASHP, so can't comment on winter running and heating h/w yet.  I'm trying to minimise costs

Hi all

I fatefully had an ashp installed in January 2020 and after a full year I am counting the cost and licking wounds.

the unit is a 16 kw LG Therma V with hydro kit. In other words it is a high temp system, with two compressors running concurrently. The outside unit looks like a monobloc ,with twin fans whilst the inside system looks like a 4ft high metal box, but contains a variable speed compressor. It generates heats up to 80c, so the radiators in my house run hot (when they are on).

My house Is 220sqm (2200sqft) and after one year of operation the electricity bill has been shockingly high whilst the system used 11203Kwh in total for hot water and radiator heating. I believe that this is excessive as the property was not well heated, we have cold areas and at least 2 rooms are not used or heated at all as we have the radiators on lowest setting. The system exceeds the predicted usage and cost by almost 40%.

The installer stated it would cost 1140GBP to run per year Last year it cost more than 1600gbp to run and the house is not even properly warm and I have to use fan heaters to supplement heating in some rooms.

I have been onto HIES to get support to get the installer to look at the set up, but I do not believe the installer has any idea about my system, based on previous experience. They just tell me that it depends on how I use it !

Can anyone recommend a professional ASHP specialist who could come to survey my system and offer advice to set up properly? I am based in Bedfordshire.

Honestly, I fear that I have made the biggest financial mistake of my life. Since purchasing it for 16000GBP, It has cost me 1600GBP in electricity, 300GbP in extra heating costs when the system broke down during 27 days in December 2020, less than a year since installation. It is noisy and intrusive both externally and internally.

I have received just 2 RHI payments so far, as the installer failed to release my certificate and they have only just installed an mmsp which RHI are refusing to accept as it does not show the correct readings. 

I do not believe that the safe guards put in place by NICIEC or HIES to protect consumers are working effectively or quickly enough. 

Sorry for the rant, but you perhaps you can understand my frustration.