Interested in a Heat Pump...

[Slippin Jimmy]

I've recently got quotes for heat pumps, and found one at £4,000 for a Mitsubishi 5/6kw Heat pump, and a 200L cylinder in the loft with 7 radiator upgrades after the gov grant. I'll be adding this onto my remortgage so it's costing a couple of quid a month for the upfront cost.

I live in a 2019, 3 bedroomed, small new build so it's very efficient, usually only need the gas combi boiler heating on for 2 hours a day max when it's currently about -1 degrees c. If i get onto the heat pump, I can cap the gas off and stop paying the standing charges for it.

I'm currently on Octopus Intelligent with my EV, and I get cheap rates of 7.5p between 23:30 and 05:30, and can get more hours of this within the day when 'charging' my car. Outside of this, it's 30p kw/h. On a usual day, I can get 7.5p kw/h between ; 09:30 - 12:00, 14:00 - 16:00, 20:30 - 22:00, 23:30 - 05:30.

 

My question is, I know heat pumps should be left on 24/7 at a set temperature. However, I could run the heat pump 4x cheaper than the normal electricity rate if I keep within those set times to reduce to 7.5p kw/h. If I set the schedule on the heat pump heating to only run between the above hours, as well as the hot water heating within those times, will it be enough to heat the house? We're comfortable with about 18 degrees, so don't need the house super hot.

[SteamyTea]

Do you know how much energy (that is the kWh, not kw/h) you currently use a day?

Knowing that is a double check on the heat pump sizing.

Assuming you have had a quite from a MCS registered company, they will have done a proper heat loss survey and report, can you get hold of that?

You may find that in future, Octopus pull your current deal, this has already happened to some of their deals.  So rerun the financial side of but with a SVR tariff.

 

kWh = energy

kW = power

[Gary68]

If you are getting a Mitsubishi Ecodan, make sure you get the Melcloud wireless add on.  With this you can set the heat pump to use different modes (fixed temp or weather comp).

 

So in the IO period you can run a hotter fixed temp and slightly over heat the house and then run weather comp during the day in the more expensive period.

 

I would look at other makes of heat pump, its sounds like your property doesn't need a lot of heat and Mitsi's don't modulate down to low power will Daikin for example are much better at that.

[Roger440]

49 minutes ago, Slippin Jimmy said:

I've recently got quotes for heat pumps, and found one at £4,000 for a Mitsubishi 5/6kw Heat pump, and a 200L cylinder in the loft with 7 radiator upgrades after the gov grant. I'll be adding this onto my remortgage so it's costing a couple of quid a month for the upfront cost.

I live in a 2019, 3 bedroomed, small new build so it's very efficient, usually only need the gas combi boiler heating on for 2 hours a day max when it's currently about -1 degrees c. If i get onto the heat pump, I can cap the gas off and stop paying the standing charges for it.

I'm currently on Octopus Intelligent with my EV, and I get cheap rates of 7.5p between 23:30 and 05:30, and can get more hours of this within the day when 'charging' my car. Outside of this, it's 30p kw/h. On a usual day, I can get 7.5p kw/h between ; 09:30 - 12:00, 14:00 - 16:00, 20:30 - 22:00, 23:30 - 05:30.

 

My question is, I know heat pumps should be left on 24/7 at a set temperature. However, I could run the heat pump 4x cheaper than the normal electricity rate if I keep within those set times to reduce to 7.5p kw/h. If I set the schedule on the heat pump heating to only run between the above hours, as well as the hot water heating within those times, will it be enough to heat the house? We're comfortable with about 18 degrees, so don't need the house super hot.

 

Why are you actually doing this. With so a low heat load, i struggle to see the logic?

 

As steamy said, what is your actual consumption? But if the boiler is only own for 2 hours, it really cant be very much.

[Slippin Jimmy]

@SteamyTea @Gary68 @Roger440

We're currently using about 1.5m^3 of gas a day. Our Bill shows that we use around 1800 kWh yearly.

It does come with a wifi module for MELCloud.

We haven't had a proper heat loss survey, that would be done once we place a deposit and decide to go ahead with it

The main reasons we're doing it is to go fully electric and remove our need for gas, and aim to save a few £'s from running in the cheap electricity rate.

We got quotes from 4 companies, they all suggested the same Mitsubishi 6kwh heat pump unit.

Edited December 4, 2023 by Slippin Jimmy
Tag and edit

[JohnMo]

14 minutes ago, Slippin Jimmy said:

use around 1800 kWh yearly

That's not even 5kWh a day including your hot water. Would expect the hot water only would account for that amount of gas. So about £215 a year including standing charge?

[Roger440]

28 minutes ago, Slippin Jimmy said:

@SteamyTea @Gary68 @Roger440

We're currently using about 1.5m^3 of gas a day. Our Bill shows that we use around 1800 kWh yearly.

It does come with a wifi module for MELCloud.

We haven't had a proper heat loss survey, that would be done once we place a deposit and decide to go ahead with it

The main reasons we're doing it is to go fully electric and remove our need for gas, and aim to save a few £'s from running in the cheap electricity rate.

We got quotes from 4 companies, they all suggested the same Mitsubishi 6kwh heat pump unit.

 

Still makes no sense. The payback period will be forever. Made worse but borrowing the money to pay for it.

[Slippin Jimmy]

Okay, I see it was a bad idea to post here. Just being told that it doesn't make sense. 

 

I just wanted to cut off my gas and go completely electric to put pressure off gas and go towards renewables. As far as I see it, the gas standing charge is paying for the upfront for the heat pump, and I'll be saving money on the gas I use on my cheap electric tariff. 

Edited December 4, 2023 by Slippin Jimmy

[SteamyTea]

Just now, Slippin Jimmy said:

Okay I see it was a bad idea to post here.

I just wanted to cut off my gas and go completely electric to put pressure off gas and go towards renewables. As far as I see it, the gas standing charge is paying for the upfront, and I'll be saving money on the gas I use on my cheap electric tariff. 

Not a bad idea to post up.

 

While you may never recover the capital cost, long term, you may be doing the right thing.

Hard to tell where energy prices are going, I suspect that there will be a convergence between natural gas and electricity prices in the medium term.

 

If you really are only using 5 kWh/day during the heating season, and say 2 of them are for showering, then you may be better off fitting PV and heating a water cylinder.

That would get the gas cost down to zero for DHW.

But when I think about it, if it is really 5 kWh/day in total, then a heat pump and PV is really the say to go.  You would only be importing energy for a couple of months a year.

[Roger440]

8 minutes ago, Slippin Jimmy said:

Okay, I see it was a bad idea to post here. Just being told that it doesn't make sense. 

 

I just wanted to cut off my gas and go completely electric to put pressure off gas and go towards renewables. As far as I see it, the gas standing charge is paying for the upfront for the heat pump, and I'll be saving money on the gas I use on my cheap electric tariff. 

 

It made no sense, because you justfied it on financial grounds. Which clearly dont stack up whichever way you look at it..

 

However, if you are doing it for ideological/ecological reasons, then fair enough.  Thats entirely your choice. But you made no mention of that. Had you done so, then the responses would probably have been different. Mine would have been.

 

Ill duck out now.

[joth]

13 minutes ago, Slippin Jimmy said:

Okay, I see it was a bad idea to post here. Just being told that it doesn't make sense. 

 

I just wanted to cut off my gas and go completely electric to put pressure off gas and go towards renewables. As far as I see it, the gas standing charge is paying for the upfront for the heat pump, and I'll be saving money on the gas I use on my cheap electric tariff. 

Yaaah It's always a risk with online forums: people love to answer a question in their head, rather than the one you ask. (I don't see "should I switch to ASHP" or "will it payback" anywhere in the OP, yet that's the Qs many love to jump on).  Although to be fair, the first few responders where on point.

 

To the question you ask, yes, if you're daily demand is 5kWh then a 6kW ASHP can achieve that in one hour, let alone 6 your have available. Caveat: it depends not just on the ASHP size, but the emitter size and their ability to put out that many kW at a lower temperature.

 

Getting an Mitsu ecodan to efficiently and effectively use Octopus cheap rate in this way takes a bit of effort. See recent discussion in this thread, for example

 

Edited December 4, 2023 by joth

[Beelbeebub]

1 hour ago, Slippin Jimmy said:

Okay, I see it was a bad idea to post here. Just being told that it doesn't make sense. 

 

I just wanted to cut off my gas and go completely electric to put pressure off gas and go towards renewables. As far as I see it, the gas standing charge is paying for the upfront for the heat pump, and I'll be saving money on the gas I use on my cheap electric tariff. 

Don't be put off. Some posters on here are rather negative on the idea of HPs.

 

As you say it's not always about the money.

 

Your gas consumption seems extremely low - which is good. 1.5m3 is about 16kwh a day! Assuming your 2 hour run time, that's about 8kw heat input.

 

I suspect your home could get by with one of the very small units like an 3.5kw Arotherm. If you were determined to stick to the low cost times you only need to "coast" through 4½ hours max. This will be dictated by the thermal.mass of your home.

 

Have you tried turning your heating off for 4 or 5 hours? Does it stay warm enough?

 

[JohnMo]

For your low usage I would just consider DHW heated on E7 or time of use tariff. Same for the heating use your heating system but in place of the gas boiler heat with an immersion. Either in a small buffer vessel with an immersion inside or a couple of Willis heaters in duty/standby. 

 

Heat pump, install would require new radiators, big cylinder and an outside unit. A even with the grant a contribution from yourself and the house pulled apart.

[Andehh]

I own a ASHP in a modern new build house and I'm happy enough with it... But your application makes no sense. Huge up front investment, more so borrowing the money, for a payback period you'll never see. Any sustainabilie benefits are lost binning a perfectly good gas boiler and radiators for a new toy.

 

Also assuming your small garden (nevause new build?), where will it go? How will you route the pipes into your property? How will you route power cables to the outside unit? They are noiser then I imagined, which in a new build small house you will likely hear, as will your neighbours.

 

Really really spend your money elsewhere, solar panels and a hot water pv booster for example!!

Edited December 6, 2023 by Andehh

[Bozza]

I agree entirely with what @Andehhhas said - I’m in the same boat & happy with my ASHP, though should be noted we didn’t have a mains gas option as are in a rural location.

 

@Slippin Jimmy you also need to factor in a number of other negatives into your proposal in addition to what’s being mentioned. You’ve described your house as being a small new build.   Firstly ASHP systems will require internal pumps - they can very noisy.  It’s unlikely a small new build will have a location for them that won’t disturb you.  To address this in our house we’ve turned down the pump speed which adversely affects efficiency.     Secondly because you wouldn’t be putting un UFH you’ll be putting in bigger rads.  They will inevitably take up much more space in smaller rooms.  Thirdly ASHP systems require installers to be very knowledgeable to install a successful system that works effectively.  A lot of ASHP installers in the UK don’t really have the experience or skills (yet) and so you are at risk of that not been the case.    Fourthly the published efficiency of ASHPs is a bit like the published MPG of cars.   We get 3x never anywhere near 4x.

[Andehh]

We did have mains gas as an option, and I'm only 70% sure ASHP was indeed the best short term solution (I don't think we will get the gov grant for our installation) . Long term I'm very confident it will be, as electric & gas prices are disconnected/swung as more renewables come online, but having watched it during a week of sub zero temps I accept there's more compromise then I was expecting.

 

Hence always warning people to really REALLY be sure ASHP is the right thing to switch to, and to never rip out a working gas system 'because ashp is in the news and everyone is discussing it'.

Edited December 6, 2023 by Andehh

[JohnMo]

40 minutes ago, Bozza said:

Firstly ASHP systems will require internal pumps - they can very noisy

No they don't require them, most installs can be driven from the ASHP circulation pump, all depends on how you design the system.

 

42 minutes ago, Bozza said:

Secondly because you wouldn’t be putting un UFH you’ll be putting in bigger rads.

Another assumption, all depends on what is currently installed. Maybe an upgrade to T22 may be needed, you don't know without running the calcs.

 

46 minutes ago, Bozza said:

Thirdly ASHP systems require installers to be very knowledgeable

45 minutes ago, Bozza said:

Fourthly the published efficiency of ASHPs is a bit like the published MPG of cars

All depends on the install design, installer not always the same person, that does the design.

[billt]

1 hour ago, Bozza said:

Fourthly the published efficiency of ASHPs is a bit like the published MPG of cars.   We get 3x never anywhere near 4x.

 

That depends on whether you look at the headline marketing guff or the actual specification. I have a Samsung heat pump and an Open Energy heat pump monitor and the performance has matched the specification pretty closely over a range of outside air temperatures. Yes it's worse in cold damp conditions, but the spec tells you that.

[Bozza]

45 minutes ago, JohnMo said:

No they don't require them, most installs can be driven from the ASHP circulation pump, all depends on how you design the system.

 

Another assumption, all depends on what is currently installed. Maybe an upgrade to T22 may be needed, you don't know without running the calcs.

 

All depends on the install design, installer not always the same person, that does the design.

 

Not so much assumptions, surely if the cylinder is in the loft he’d need additional pumps?  Happy to be corrected if that is technically wrong.  Regarding my upgrading of rads observation unsure why you are critical of that as your earlier post also observed “Heat pump, install would require new radiators”  unless you are meaning bigger BTUs doesn’t necessarily mean physically larger rads in which case yes I agree that’s a fair point but generally double panels are thicker (bit like me sometimes), but yes it is an assumption, though quite likely, he’ll need bigger whether wider, taller of thicker.  

 

my point re installers etc.  yes agree with your point,  the point I’m making though to OP is highlighting the risk with so many dodgy or inexperienced installers around not putting in correctly designed systems and having problems with them.

 

 

 

[Bozza]

21 minutes ago, billt said:

 

That depends on whether you look at the headline marketing guff or the actual specification. I have a Samsung heat pump and an Open Energy heat pump monitor and the performance has matched the specification pretty closely over a range of outside air temperatures. Yes it's worse in cold damp conditions, but the spec tells you that.

Exactly the point trying to highlight to OP I think a lot of people have read marketing guff and expected to get higher efficiency than they actually achieve in real life.  Yeah I get pretty much what I expected too.  I probably should have said “advertised” rather than “published”.   

[Beelbeebub]

39 minutes ago, Bozza said:

Not so much assumptions, surely if the cylinder is in the loft he’d need additional pumps?  Happy to be corrected if that is technically wrong.  Regarding my upgrading of rads observation unsure why you are critical of that as your earlier post also observed “Heat pump, install would require new radiators”  unless you are meaning bigger BTUs doesn’t necessarily mean physically larger rads in which case yes I agree that’s a fair point but generally double panels are thicker (bit like me sometimes), but yes it is an assumption, though quite likely, he’ll need bigger whether wider, taller of thicker.  

 

my point re installers etc.  yes agree with your point,  the point I’m making though to OP is highlighting the risk with so many dodgy or inexperienced installers around not putting in correctly designed systems and having problems with them.

 

 

 

Most* monoblock HPs have a pretty powerful built in pump.  For example the grant/chofu HPs have 10m or 12m head.  It's unlikely he will need a additional pump, those are only needed for very big and complex systems.  In fact if he has UFH fitted downstairs he may need to remove that pump and run direct.

 

Historically, installers have often put big hydraulic buffer tanks in, which do need additional pumps, but the thinking now is to run the systems with a few "bells and whistles" as possible.  The ideal is a single 3 port valve and no zoning.

 

If (big if) his heating system was designed with a 55C flow temp, which was recommended in 2019 but not an actual requirement then the HP should be able to run at about 45C to give a similar output on those rads (the mean flow temp of a radiator spec'd for a boiler flow temp of 55C is 45C because they have DT of 20C across the rads.  A HP has a smaller DT of about 5C so will have a Flow temp of 47.5C for the same mean rad temp of 45C)

 

One test would be to turn his boiler flow temp down to 55C (or lower) and see how he goes.  If his house is nice and warm with a 55C or lower flow temp, then he probably doesn't need any significant changes to his heating system.

 

 

*I believe the Samsung Gen6 monoblocks use an external, customer supplied, pump.

[Beelbeebub]

38 minutes ago, Bozza said:

Exactly the point trying to highlight to OP I think a lot of people have read marketing guff and expected to get higher efficiency than they actually achieve in real life.  Yeah I get pretty much what I expected too.  I probably should have said “advertised” rather than “published”.   

It does need to be made clearer that "more efficient" doesn't necessarily mean "cheaper". 

 

Unless you HP install is terrible (and historically some have been) you will almost always be ahead in terms of carbon emissions.  If your first priority is dropping those, then a HP will do that.

 

But in order to actually be cheaper, especially with the higher up front cost of a HP, then your install does have to better than has perhaps been typical in the industry.

[RobLe]

Is there anywhere inside your thermal envelope to put that cylinder?  Most lofts are very cold, and there’d be a lot of extra loss from a 200l tank and all the gubbins associated with it.  Failing that, can you make an insulated room for it perhaps?

I expect a lot of your useage is dhw rather than heating at that very low level, which is commendable !  Perhaps one of those water heater type heatpumps would then be appropriate (eg Vaillant aroSTOR, although there are many makes).  If you’re grant eligible, I expect that rather skews things towards something more standard.

[Alan Ambrose]

>>> But in order to actually be cheaper, especially with the higher up front cost of a HP, then your install does have to better than has perhaps been typical in the industry.

 

Is the logic here 'electricity is 3x price per kW than gas, so you need an average CoP > 3 (to swap out a gas boiler for a HP) and you'll only get that with a very good HP install'?

[joth]

1 hour ago, Alan Ambrose said:

 

Is the logic here 'electricity is 3x price per kW than gas, so you need an average CoP > 3 (to swap out a gas boiler for a HP) and you'll only get that with a very good HP install'?

Sort of. You only need an "adequate" installation to achieve COP of 3, I'd say the nuance here is that the typical UK installation in below adequate.