ASHP - E7 or not E7?

[martian]

Just wondered if anyone has experience of running an ASHP using the cheaper rate economy 7 tariff and whether it makes any real difference in running costs. I seem to remember that you have to pay a slightly higher day rate if you have E7, and that, coupled with the fact that the ASHP would be running at night when it might be cheaper but also colder would seem to maybe cancel any financial benefit. Also, it seems that running an ASHP 24/7 makes better sense and it's unlikely to be able to run an ASHP on normal rate during the day and E7 at night.

Thanks in advance to anyone who can shed some light on my ignorance!

[ProDave]

For me the killer is the inflated daytime rate and usually higher standing charge.  It would probably be possible to do all your heating at night but then if someone uses up all the tank of hot water I would want it replenished and not be rationed to one tank of HW per day, which would mean daytime rate.

 

The final nail in the coffin is we have solar PV so want to use the ASHP as much in the daytime as possible to self use that and as little as possible at night.

[Temp]

Is there anything to stop a house having two electricity supplies/meters from different companies and switching between them ?

 

One supply on E7 only used at night.

One with cheap daytime rate only used in the daytime.

 

Two standing charges and problems with your address on the databases?

 

Switching needs to be synchronised to a zero crossing (or use a UPS?) to avoid loss of power during changeover?

 

I'm guessing there are regulatory problems?  

 

 

 

 

Edited August 5, 2021 by Temp

[willbish]

Not yet in my selfbuild with ASHP but planning on getting an E7 meter.

 

At the moment I'm living in a flat with E7 meter but we were unable to shift enough of our consumption to the off-peak hours to justify the expensive on-peak rate. This was easily fixed by switching to a regular tariff  (same both day and night) with no need to change meter. 

 

[PeterW]

8 hours ago, martian said:

Just wondered if anyone has experience of running an ASHP using the cheaper rate economy 7 tariff and whether it makes any real difference in running costs

Yes it’s called load shifting - works really well. 
 

8 hours ago, ProDave said:

The final nail in the coffin is we have solar PV so want to use the ASHP as much in the daytime as possible to self use that and as little as possible at night.

Probably one of the better reasons for solar PV although in winter you need a lot of panels to offset the usage 

[Ommm]

1 hour ago, willbish said:

Not yet in my selfbuild with ASHP but planning on getting an E7 meter.

 

At the moment I'm living in a flat with E7 meter but we were unable to shift enough of our consumption to the off-peak hours to justify the expensive on-peak rate. This was easily fixed by switching to a regular tariff  (same both day and night) with no need to change meter. 

 

 

I've had no end of problems switching supplier where they got the night and day readings mixed up (in different properties too).  I'm waiting for Octopus to line me up with a smart meter so that they can push an E7 tariff to my meter if they want to, but will probably stay on the regular tariff.

 

Although you could do something funky by switching tariff mid-year: E7 for the summer, regular tariff for the winter?  Even more interesting if you have solar PV where you can offset the expensive day rate with your own generation.  Still probably makes more sense to be on Octopus Agile or one of the EV tariffs though.

Edited August 5, 2021 by Ommm

[SteamyTea]

9 hours ago, martian said:

with the fact that the ASHP would be running at night when it might be cheaper but also colder would seem to maybe cancel any financial benefit

The efficiency does not drop that much.  E7 night rate is generally a shade under half the daytime rate, your CoP would therefore have to halve.

 

 

[TerryE]

52 minutes ago, SteamyTea said:

The efficiency does not drop that much.  E7 night rate is generally a shade under half the daytime rate, your CoP would therefore have to halve.

 

You have to do the sums.  The CoP does go down with temperature, but I suspect that the day - night drop is rarely over 10°C and this typically drops the CoP by less 1 one so as long as you do most DHW heating, washing machine and dishwashing overnight, then I suspect that you'll still make a material saving.

[joth]

16 hours ago, Temp said:

Is there anything to stop a house having two electricity supplies/meters from different companies and switching between them ?

 

Think you're  only allowed one meter per MPAN and there would be a lot of regulatory challenges in having the house swap between live suppliers. If you have 2 MPANs (supply heads) they'll probably be on different phases so even harder to swap between (zero crossing impossible)

my guess is the 2x standing charges will kill any savings anyway

 

 

Anyhooooo a lot of the current policy development is in smart meters is enabling [much] smoother change of supplier, and I did see it outlined on one of the white papers on https://www.smartdcc.co.uk/  that the goal is ~realtime change over so you could change suppliers hour by hour. Idea is to open it up to  hyper local suppliers that can resell  solar between neighbours and stuff. Don't hold you breath, may happen in a couple decades.

 

 

[Far2wired]

We recently switched to Octopus Go, it is designed for people with electric cars but we have set our battery inverter to charge up at its E7 equivalent rate. Once I have access to our HP LG controller (password locked by installer) will be looking at setting that too to make use of the cheaper electric.

 

Unit rate (04:30 - 00:30) 16.26p kWh 

Unit rate (00:30 - 04:30) 5p kWh

 

[ProDave]

On 05/08/2021 at 22:34, Ommm said:

I've had no end of problems switching supplier where they got the night and day readings mixed up (in different properties too).  I'm waiting for Octopus to line me up with a smart meter so that they can push an E7 tariff to my meter if they want to, but will probably stay on the regular tariff.

I had that nightmare in a previous rental property.  When we got vacant possession back and submitted meter readings they were all wrong.  It took months to unravel.  I had a meter reader out twice, and both times we agreed what the readings were but when they got submitted they were swapped, it's as of the computer algorithm's saw an "error" and automatically swapped them.  When they finally agreed there was an error, they had to trace the last two tenants to "correct" their bills.

[ProDave]

55 minutes ago, Far2wired said:

We recently switched to Octopus Go, it is designed for people with electric cars but we have set our battery inverter to charge up at its E7 equivalent rate. Once I have access to our HP LG controller (password locked by installer) will be looking at setting that too to make use of the cheaper electric.

 

Unit rate (04:30 - 00:30) 16.26p kWh 

Unit rate (00:30 - 04:30) 5p kWh

 

That post was a big "Whoa, hold on what's going on here" post.

 

I am currently with Octopus and I am on their variable tariff (any fixed tariff currently on offer is higher) and currently paying   18.47p per kWh and  25.99p daily standing charge.

 

So I looked up this Octopus go tariff and got the "quote for your area" that includes the distribution surcharges (high up here)  It came back with 16.9p per kWh and 25p daily standing charge.

 

So IF I switched to Octopus go, I would get a cheaper day rate, a lower standing charge, and the 5p rate for 4 hours at night (that I could use to heat the DHW by the ASHP and pre heat the house a bit for the day in winter)

 

What am I missing?  I have always avoided off peak tariffs because traditionally they come with a higher day rate, but if I can get a cheaper day rate as well it seems a no brainer.

 

Only 2 issues.  I would have to get a smart meter (ugh) and I would have to pretend to have an EV (we do have a hybrid)  do they actually check you have an EV or not?

 

Now I generally like Octopus because their customer service is pretty good and they are quite flexible with the control a user has over how they operate their account, BUT I feel VERY irked, that every time I have looked to see if they offer a cheaper tariff, they have NEVER mentioned Octopus go and how much I could save by switching to that.

[Temp]

Indeed, I just got a quote and it wasn't mentioned.

 

https://octopus.energy/go/

 

Says..

Octopus Go is a beta product. If you're OK that some things may not work first time, that installations and processes may take longer than we'd like, and that on occasion data issues with smart meters can take significant time to fix or prevent things working at all, but that you'd like to work with us to make world-changing energy tariffs a reality, check this box so we know you're onboard. You will always be able to switch to one of our fairly priced standard tariffs at any time. I'm ok with this!

[ProDave]

My remaining reservation is this cheap tariff is a "loss leader" to persuade me to get a smart meter (from which there is no going back) and won't last long before it creeps up to higher rates?

[joe90]

Didn’t @canalsiderenovation have octopus go? And had problems with double charging?

[ProDave]

24 minutes ago, joe90 said:

Didn’t @canalsiderenovation have octopus go? And had problems with double charging?

Thanks.  I have just posted in that thread to see how she is getting on.

 

So if I switch to go I would save 1.67p per kWh on the "day" rate, so based on my annual usage would save £118 per year, plus another 0.99p per day in standing charge or £3.61 so lets call that a saving of £120pa plus whatever I would save by shifting ASHP load to the 4 cheap hours.

 

Is that saving worth the potential problems that @canalsiderenovation had?

[DragsterDriver]

1 hour ago, ProDave said:

My remaining reservation is this cheap tariff is a "loss leader" to persuade me to get a smart meter (from which there is no going back) and won't last long before it creeps up to higher rates?

 Our bills doubled with a smart meter. If you suspect your smart meter is wrong you have to pay upfront to have it tested- by your supplier. Huge mistake getting one.

[joe90]

54 minutes ago, ProDave said:

Is that saving worth the potential problems that @canalsiderenovation had?

I do think she has sorted it out now tho. Regarding going E7 I think it was @SteamyTea (who had logging access to my usage) to say in my case it would be marginal wether a benefit or not but will consider it a “plan B” in case circumstances change.

 

i do remember Jeremy Harris saying smart meters needed a mobile signal so may not work everywhere anyway.

[ProDave]

Okay, a question for those on Octopus Go:

 

The 4 hour 5p rate at niight, is that on GMT (like E7) or is that local time?

 

i.e. would I have to change my programmer (which works on local time) between seasons (it is it on fixed GMT times)

[ProDave]

I am still considering this, but SWMBO has veto'd running the ASHP for the 4 cheap night rate hours.  The issue is when the HP is on, there is a low level noise audible from the circulation pump, and at the moment we deliberately don't run the heating at night so it is silent.

 

So if I were to switch, it would not be to make particular use of the 4 hours at 5p, rather for the general savings.  So switching to GO would save me 1.67p per kWh on the day rate, so that would save about £100 per year.  I would not go to all the hassle of changing energy supplier for that small saving.  The question is, is that enough of a bribe to get me to accept a smart meter and then any hassle that goes with it if the thing proves incapable of providing the correct readings?

 

 

[jack]

13 minutes ago, ProDave said:

The question is, is that enough of a bribe to get me to accept a smart meter and then any hassle that goes with it if the thing proves incapable of providing the correct readings?

 

I think serious issues with the latest generation smart meters are pretty rare. Ours (on Octopus Go) seems to work perfectly. 

 

On your other question, we do have an electric car, but from memory Octopus didn't ask us to even confirm that when we signed up for the Go tariff, let alone require any evidence.

[Geoff-Belgraver]

I have a fully costed ASHP installation project for my home, but have decided not to proceed because of the capital cost, the complexities involved in complying with the RHI requirements for retaining the gas boiler as a hybrid and the anticipated electricity costs for normal running hours

 

Instead I am investigating a self-install hybrid ashp+existing gas boiler with hot water buffer storage option using low-tariff electricity when costs are at their lowest.  Agile Octopus or Octopusgo would appear to be suitable.

 

I have sufficient room for the required heavily insulated 6m3 hot water tank and the ashp away from the house. From gas usage data already  collected, I estimate that I'll need approx. 13kW heat pump to achieve the required peak heat input over a 4-hour period during coldest weather.

 

My primary objective is to reduce my carbon footprint.....

 

Has anyone done anything similar?

[IanR]

27 minutes ago, Geoff-Belgraver said:

complexities involved in complying with the RHI requirements for retaining the gas boiler as a hybrid and the anticipated electricity costs for normal running hours

 

What's the issue making you retain the Gas Boiler?

 

What SCOP do you have estimated for the ASHP, that gives rise to issues with the anticipated electricity costs?
 

27 minutes ago, Geoff-Belgraver said:

I have sufficient room for the required heavily insulated 6m3 hot water tank

 
6m³ hot water tank, 6000l, really? Is this just for a domestic property or is there more to this install?
 

Quote

My primary objective is to reduce my carbon footprint.....

Loose the Gas Boiler?

Edited September 14, 2021 by IanR

[Geoff-Belgraver]

1. What's the issue making you retain the Gas Boiler? - The Ideal Mexico CH125 is so simple and 82% efficient, so will be there on standby as I have plenty of room. I just can't see any reason for not keeping as as back-up. When (not if) an ASHP fails in mid winter what are the options other than an expensive emergency call-out - also assuming that replacement parts are immediately available? We don't want to be cold.....
2. 6m³ hot water tank, 6000l, really? -Take max heat off ASHP at SCOP 25 for max winter demand of 130kWh per day & store it all for daytime use. (I have gas usage data going back years) My CH water flow is normally ~55 deg C.
3. Is this just for a domestic property? -  When you live in a Victorian House in a conservation area with no simple options for insulating the walls, there are not many options.....
4. reduce my carbon footprint.....? I'm assuming gas will be no more than 10% in the 8 winter months - The initial, fully worked quote from one of the major ASHP suppliers showed that gas would probably never be used.

[SteamyTea]

27 minutes ago, Geoff-Belgraver said:

When (not if) an ASHP fails in mid winter what are the options other than an expensive emergency call-out

10 quid fan heaters, it will not be long until the carbon content of our electricity supply will be 50g?kWh which will beat combustion technologies hands down every day.

 

 

29 minutes ago, Geoff-Belgraver said:

6m³ hot water tank, 6000l, really? -Take max heat off ASHP at SCOP 25 for max winter demand of 130kWh per day & store it all for daytime use. (I have gas usage data going back years) My CH water flow is normally ~55 deg C.

This is not how you set up a heat pump system.  130 kWh / 24 h is a power of 5.4 kW, which is ASHP terms is about as small as you can get.