A2A 6 months in

[Gill]

Thought I'd come back with how the A2A journey has been going so far.

 

We fitted 2 x 2.5 kw and 2 x 3.5 kw indoor units with 2 outdoor in our bungalow to replace 5 storage heaters.  Aside from a couple of tests of the AC in summer, it wasn't until September they saw much action. We haven't changed energy tarrif so still eco 7.

 

I'd love to have some like for like stats on energy usage but there are quite a few moving factors.

 

- Old draughty double glazed widows replaced with triple glazed early this year

- Underfloor insulation in the suspended floor void

- Standalone garage converted into a granny flat with building work starting in July and finishing in November.  Build work put a bit of an increase in our daytime electricity and since completion we've had friends stay (10 days total) and I'm heating it on the two or three days a week I'm not in the office. The granny flat has a single 2kW panel heater. 

- Last year was our first year in the place and we were baltic for much of October /November until we gave up with wearing 12 layers and accepted we needed to top up heat with peak heat when the storage heaters were no longer keeping the temperature above 16. After that, we decided to try to accept the cost, be comfortable (no more than 3 jumpers) and get baseline of what our energy needs really were. 

 

I thought I'd share the stats I have. 

September, October we're down on usage and cost which was a bit of a surprise given building work. I put that down to running heating only for an hour or so when needed and probably a good COP as the temps hadn't dipped way down. 

November we were up on usage and cost. Not surprising as I was running heating and dehumidifier in the granny flat to draw out last of the moisture, we had a cold snap that coinsided with friends staying in there for a few days.  As I mentioned, last year we were trying to avoid top up peak heat which we gave up on as it was making us miserable. 

December is looking really positive. We've had family round for Xmas day as per 2022 so whole house and sunroom set to sauna ++ to keep the oldies from feeling a chill.  This year it was much easier to heat the place and much warmer than last year. One other event that meant whole house and sunroom heating was cranked up again. We've also had young ones in the granny flat this week who are unfamiliar with short showers and off switches. I think we're likely to be £450 this month vs £670 December 2022. (Admittedly Dec last year have a good week + of very low temps where we were going through 80kWh daily). 

 

I'm not entirely trusting of the SP app but supposedly it is comparing last year to this year using current prices.  If our December saving is comparable to Jan and Feb then hopefully we'll be saving around 500 over those months alone and enjoying more responsive and comfortable heating. 

 

Worth noting for balance -

ROI not taken into account.  Come July potential saving should be clearer (unless we fast track on our solar plans) .   New system was about 9k fitted.

It will have annual maintenance overhead unlike the storage heaters. System lifespan isn't going to be anything like that of storage heaters. 

Defrost cycles in very cold weather are regular (quite short periods so far even at - 6). Pure luck that the indoor units we tend to run together when very cold are connected different outdoor units. 

We opted for high wall mounted units so there's still the cool air pocket down low issue. I do wonder if a ceiling fan might help. 

It's a different type of heat which takes a bit of getting used to. As the room comes to temp, there's the feeling of cold draft as the air circulates. I find that's avoided if I don't try to crank the heat up very quickly but instead set a timer to give it 1 hour to come up to desired temp. 

 

All in ALL, very happy we made the switch and wondering if I'll regret not putting it into the granny flat.

Much appreciated all the BH help and advice that went into my lengthy decision making 😁

 

[MikeGrahamT21]

Certainly a good reduction in kWh comparing the two years, the weather will have helped this December too, had some very mild days.

 

How many m2 are you heating?

[Gill]

58 minutes ago, MikeGrahamT21 said:

Certainly a good reduction in kWh comparing the two years, the weather will have helped this December too, had some very mild days.

 

How many m2 are you heating?

 

Yes, the mild December has definitely been a bonus. More winter months before I can get too optimistic but I'm quietly hopeful. 

 

We can now be even more inconsistent with what we heat which doesn't make for great measurements or comparisons. 

 

• Living room.  Room size 105 m3.  Heated evenings /weekends /holidays. Till mid Nov heated 2 to 3 days a week when I wasn't working in the office. Usually set about 22.
• Bedroom.   Room Size  40m3.  Heated when temps are low only. It benifits from the living room unit as we're open ish plan. It helps avoid the living room unit working too hard when it's very cold. Set around 18. 
• Bedroom 2.  Office room / spare bedroom.  Room Size  36m3.  Heated when used as office by OH (3 days a week). Overnight +dehumidifier for winter laundry. Or guest staying and no longer being baked overnight. 
• SunRoom.  Room size 68m3. Winter only if we're having big family / friend gathering. Twice only this winter so far. Last year just once on Xmas day. 
• Hall & kitchen only gets heated if very cold and then we leave bed 2 door open and run that unit at around 19. 
• Bathrooms we don't heat. Rarely use one off hall and our main absorbs heat from bedroom or living room 

Unit placement was adjusted a little from pic. Sun room unit is centre of wall and bed 2 unit went on outside outdoor unit wall.  Working well for our current layout. 

 

Last winter the living room, main bathroom storage heaters were always on at some level after November. Bed 2 only when OH was working at home. Kitchen and hall consistently baltic. 🥶

Edited December 30, 2023 by Gill

[Crofter]

@Gill those room sizes are enormous! Is it a ft²/m² mixup??

Thanks for posting the update, really useful for someone like me considering making the switch soon.

[Ferdinand]

Thanks for posting the information - it highlights for me how different it all is for different people / living arrangements.

 

Mine are on a separate thread somewhere, but are completely different as I am running low background gas ufh and playing around with a biggish portable A2A unit with a view to maybe installing first as an alternative to gas, then mainstay, then replacement. Larger 4-bed house but no one here except me and the last bit of the Christmas turkey (which is actually gammon).

 

My gas ufh is not very responsive, so I may start with A2A downstairs when I do for responsiveness. Upstairs is gas rads on a separate circuit. Apparently the time to have them fitted is winter when demand is low.

 

And well done on your reduction.

 

I'd suggest keeping a careful eye on the annexe - a 2kW direct panel can run up a lot of electric if used fairly constantly. There are through the wall heat pump based heat / cool / dehumidify A2A units designed for apartments which may be appropriate.

Solar in the future? 😉

 

(I can't get my head around the room sizes either, nor spot an obvious unit crossover that could generate the numbers.  The plans are a great help.)

[joth]

4 hours ago, Crofter said:

@Gill those room sizes are enormous! Is it a ft²/m² mixup??

The quoted sizes are m3 so room volume not area. Looks about right vs plans for 2.7m ish ceiling heights.

 

@Gill are you able to make use of the E7 cheap rate at all now? Planning a battery, or moving to a different tariff might reduce running costs assuming you aren't running the a2a all night. 

Edited December 31, 2023 by joth

[MikeGrahamT21]

6 hours ago, Crofter said:

@Gill those room sizes are enormous! Is it a ft²/m² mixup??

Thanks for posting the update, really useful for someone like me considering making the switch soon.

@crofter they’re m3 so assuming normal ceiling height divide by 2.4 for m2.

if ceiling height is right your around 11kWh/m2 for this month.

 

Edited December 31, 2023 by MikeGrahamT21

[Gill]

1 hour ago, joth said:

The quoted sizes are m3 so room volume not area. Looks about right vs plans for 2.7m ish ceiling heights.

 

@Gill are you able to make use of the E7 cheap rate at all now? Planning a battery, or moving to a different tariff might reduce running costs assuming you aren't running the a2a all night. 

 

I think my volumes are right. We do have really quite hight ceilings for a bungalow. It's not traditional - previously was a substation so our living room has very high ceilings. 

 

E7 is still getting used for DHW, dishwasher, washing machine. Prior to holidays I'd use to warm living area before I'm up and out for work. With the holidays, that's switched off as I'm not up at 6. I'm quite liking a consistent temp for sleeping so one is sometimes kept on low if the temps have really dipped. 

 

I was interested again in batteries now (Feb 2024) the vat saving is not tied to solar instal. Our long term solar plan needs the 'to reroof or not' question answered so all went on hold this year. 

 

I need to do some more maths but last I was looking at a givenergy AIO, the ROI was getting where I need it to be. Think that was based on switching to a tarrif that would allow me to fully charge and discharge battery twice daily in winter (if such a tarrif exists) so potentially away from eco 7.  The battery wouldn't be a money saver so much as added convenience especially when solar comes into the picture. It would also be nice to have some degree of backup in a power out given we have nothing else heating /powering the house. 

4 hours ago, Ferdinand said:

I'd suggest keeping a careful eye on the annexe - a 2kW direct panel can run up a lot of electric if used fairly constantly. There are through the wall heat pump based heat / cool / dehumidify A2A units designed for apartments which may be appropriate.

I'm going to keep a close eye. My initial thought was is wasn't worth the investment for 5 months where heating on and average 2.5 days a week but I didn't think about overheating in summer so another thing on the monitor list. The place was stripped back to brick, reroofed and insulated up so it actually benifits from a blast of eco 7 between 5 and 7 to bring temp up and then it's just top up during the day. I could do with a monitor mind you just for my curiosity. 

Edited December 31, 2023 by Gill

[SteamyTea]

1 hour ago, Gill said:

E7 is still getting used for DHW, dishwasher, washing machine. Prior to holidays I'd use to warm living area before I'm up and out for work. With the holidays, that's switched off as I'm not up at 6. I'm quite liking a consistent temp for sleeping so one is sometimes kept on low if the temps have really dipped.

I don't understand your heating regime at all.

Are you saying you don't turn on your heating to take advantage of E7?

Washing machine and dishwasher are relatively low usage.

[ProDave]

If you are not really using E7 and only a small amount of your usage is in the off peak times, then seriously consider switching to a single rate tariff.  At the moment you will be paying higher for the day rate than you need to which is most of your usage.

 

 

[Crofter]

1 hour ago, ProDave said:

If you are not really using E7 and only a small amount of your usage is in the off peak times, then seriously consider switching to a single rate tariff.  At the moment you will be paying higher for the day rate than you need to which is most of your usage.

 

 

This is what I'm wrestling with at the moment for my planned upgrades next year.

E7 only makes sense if you can shift loads and store energy in the form of hot water, or in a battery or EV.

If you used energy at a constant rate through the day and night then you're better off on a flat rate tariff.

[SteamyTea]

4 minutes ago, Crofter said:

store energy in the form of hot water, or in a battery or EV.

And storage heaters.

[Gill]

1 hour ago, SteamyTea said:

 

Are you saying you don't turn on your heating to take advantage of E7?

 

If we're going to be home early in the day I'll warm up rooms on e7. If say for example today, I'm out all morning and the temperature isn't too low then no point as the heat will have gone by time time I'm back. If temps are very low then the heating will run all all night to avoid the house base temp getting very low. I also heat the granny flat on e7 when I know ill be working in there so minimal day time top up. This winter is very much experimental to see what works and what doesn't.

 

Edit - also left one storage heater wired up in case I'd undersized the A2A system as fail safe. Haven't used it as yet but was another reason I didn't switch off e7 just yet. 

 

1 hour ago, ProDave said:

If you are not really using E7 and only a small amount of your usage is in the off peak times, then seriously consider switching to a single rate tariff. 

 

That's the maths I need to do. I'm sure at the moment we're better on flat rate. Summer we'd be better on e7 for dhw as we don't run heating or cooling. Put a battery in the mix and time of use tarrif would probably work very well for us year round. I've heard suppliers are unlikely to switch you back to e7 if you move away from it but not sure if that's still accurate. 

Edited December 31, 2023 by Gill

[Gill]

The maths so far. Tight margins. Still seem to be better on E7 unless I'm messed up my maths. 

 

 

End of August to 31 Dec

 

1855 day  x    0.32797 £608.38

1078 night x 0.1622£ 174.85

 

Total £783.23

 

2933 x  0.2816 (Octopus standard) £825.93

[ProDave]

And in the summer when there is no heating?  I bet you are worse off on E7?

[SteamyTea]

@Gill

 

From tomorrow, work out what the energy usage of your DHW is.

That really seems, to you, your big unknown.

 

Measure, measure, measure.

It will tell you what you need to know.

[TonyT]

Buy a battery and time shift consumption.

[SteamyTea]

3 minutes ago, TonyT said:

Buy a battery and time shift consumption.

Every £1000 spent on a battery could buy 6.6 MWh of E7 (@ tomorrows EDF rate of 15p/kWh).

[Crofter]

1 hour ago, SteamyTea said:

And storage heaters.

It's cheaper to run ASHP on peak rate than storage heaters on cheap rate.

[Crofter]

7 minutes ago, SteamyTea said:

Every £1000 spent on a battery could buy 6.6 MWh of E7 (@ tomorrows EDF rate of 15p/kWh).

But without the battery you can't really use that 15p electricity.

[Gill]

19 minutes ago, SteamyTea said:

@Gill

 

From tomorrow, work out what the energy usage of your DHW is.

That really seems, to you, your big unknown.

 

Measure, measure, measure.

It will tell you what you need to know.

Around 6 daily for the water. In the summer that's our biggest use and only ever heated on E7. 

[SteamyTea]

1 minute ago, Crofter said:

It's cheaper to run ASHP on peak rate than storage heaters on cheap rate.

Generally yes.

There may be the odd day when the temperature is silly low and the units are defrosting more than usually, but they would be very rare days.

 

1 minute ago, Crofter said:

But without the battery you can't really use that 15p electricity.

Well I do.

For this year, until December, my mean E7 power is 0.872 kW and the day usage is 0.077 kW.

That will look a bit better come tomorrow as I did not turn the storage heaters on until this month.

[SteamyTea]

13 minutes ago, Gill said:

Around 6 daily for the water.

Then that is £350/year.

If you got an Ecocent type water heater, then you may get that £150/year (if you run it at night).

Not much difference if you change to a fixed rate tariff.

Edited December 31, 2023 by SteamyTea

[TonyT]

42 minutes ago, Crofter said:

It's cheaper to run ASHP on peak rate than storage heaters on cheap rate.

Surely that depends on the day/night tariff and the Cop

[Gill]

1 hour ago, SteamyTea said:

Then that is £350/year.

If you got an Ecocent type water heater, then you may get that £150/year (if you run it at night).

Not much difference if you change to a fixed rate tariff.

 

Was mildly surprised fixed rate isn't actually cheaper.  Maybe a cold Jan /Feb will mix it up again but for now I'll stick with the E7 and keep checking the maths. 

 

Looked into those ecocent type systems a while back and just too expensive with no plumber up my way having the slightest idea about them.  I suspect any repair costs could add up. Probably go solar and UVC when I can motivate myself to get into 2024 refurb action.