Does an ASHP stack up financially?

[SBMS]

4 minutes ago, Temp said:

 

Are you sure..

https://www.globalpetrolprices.com/United-Kingdom/lpg_prices/

69.3p/L

 

As for running cost comparison.. the only Web site I know that does a half decent job is here...

https://nottenergy.com/resources/energy-cost-comparison/

Scroll down to the table and see "Pence per kWh (after boiler efficiency)"

 

 

 

Hi Temp - yes, as mentioned my parents have just signed up (here in Lancashire) for 38ppl fixed for 2 years with extragas. I think the LPG prices on nottenergy as based on variable non fix. But wholesale LPG commodities are now increasing in line with natural gas so its likely that price is going to shift over next few months.

[joe90]

8 minutes ago, Iceverge said:

I came to the conclusion that there is no two houses alike and even if there were, no two sets of occupants would behave the same. Calculations and modelling only go so far.

+1, I have a large south facing conservatory and believe this heats the house a lot of the time. I did no modelling at all, just finger in the air (using knowledge from many members here).

[SBMS]

11 minutes ago, Iceverge said:

Pondering heating systems can be like pondering how to climb Everest from base camp for self builders. Its impossible to know the exact best route without first knowing the best route. 

 

I gave nights upon nights considering this. I came to the conclusion that there is no two houses alike and even if there were, no two sets of occupants would behave the same. Calculations and modelling only go so far.

 

Objective data is impossible to find, every consumer with a novel system thinks their own goose a swan. Every installer is prejudiced by familiarity and margin on installation. Every salesman only wants to pander their wears. I got so fed up with all this going around in circles I decided not to install any heating at all. Bold, rash, stupid, maybe, but if we were going to part with heaps of our cash I wanted to be sure. 

 

We built to passive house standards, a little beyond in theory. Put a direct UVC for DHW on night rate electricity. I borrowed a 2kW electric heater, plugged it in in the hall, and got to work regularly recording the electricity meter and feeding the results into a spreadsheet. Over a few months it was possible to isolate the DHW usage and now I'm working on the space heating. By March I'll have a full year of data of exactly our usage, to the kWh. No guesswork, no modelling estimates, just two numbers. DHW and space heating.

 

So far DHW 10kWh/day for 2 adults and 2 small children. Space heating is broadly in line with PHPP, maybe slightly more. I must get a thermal imaging camera to check for any weak thermal spots. Also it's been very dull. I'll know more soon.  I have aims for an A2A heat pump and solar PV. When I have my exact usage I'll be able to estimate if they're worth it. 

 

In hindsight I think we should have installed UFH pipes and run them from a Willis heater. While my current radiator was free, anything that I'd actually like to look at in the house permanently certainly isn't.  Also , half our heating is on expensive day rate electricity. With UFH and a willis heater we could shift it all to cheap night rate with the slab as a storage heater, like @TerryE

 

It wouldn't have been much hardship to get an UVC with a heat pump coil to futureproof also.   

 

 

TLDR:

1. Pathologically minimise your heating demand in design and construction stage.  

2. Install UFH + willis heater  and a heat pump compatible UVC. 

3. Run your house for a year on E7. 

4. Use the data to make the best decision. 

 

 

 

 

 

 

 

 

 

Interesting concept @Iceverge. Would the engineer, data-geek in me love to try this to arrive at a data-driven decision? Yes. Would my 'nesh' wife who stabs the boost on our current wall stat so much its fallen off, let me? Not in a million years.

[ReedRichards]

32 minutes ago, SBMS said:

Would a cylinder for a gas boiler be compatible with an ASHP or would that need replacing too?

 

You would need to check your specifics but heat pump cylinders need to be heated with lower temperature water.  You need to heat the cylinder quite quickly as the heating to the house is off whilst the cylinder is being heated.  So heat pump cylinders typically have longer coils with a larger surface area.  

[nod]

1 hour ago, SBMS said:

The current draft regulations seems to specifically include self build properties, see regulation 7 in the DES’ draft legislation for the boiler upgrade scheme:

 

Requirements for new-build properties
7. A property meets the requirements in this regulation where—
(a) any building that forms part of that property was built principally with the use of the labour or resources of the first owner (including where the resource was a loan which the first owner was liable to repay), and
(b) the property has not, while the building was built or at any subsequent time been owned wholly or partly by a person who is not an individual.

 

from:

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1040470/Draft_Boiler_Upgrade_Scheme__England_and_Wales__Regulations_2022.pdf

 

so it does look like 5k grants are available for self builders, just not property developers. Would welcome anybody else’s interpretation of the regulations!

Good news if your interpretation is correct 

I assumed that the change in April would leave us with a better grant or at lest the same 

 

In fairness We we’re both disappointed with the build show Very different to all the others we have been to 

The vast majority seemed to be sales people drafted in for the show 

With no technical knowledge 

[joth]

51 minutes ago, SBMS said:

This is really interesting - is this a recent quote? A 3k price differential in capital outlay is certainly compelling. We are not at the quoting stage yet so perhaps my assumption that ASHP install costs would be 5-10k higher than gas are simply wrong. Are you currently building?

My guess is if you quote for the very cheapest LPG combi boiler and then look at the difference to upgrade to ASHP + UVC + buffer tank then it looks a bit expensive. But if comparing like for like, including a mains pressure DHW with UVC in either case, then it's a lot more palatable.

 

[SBMS]

14 minutes ago, ReedRichards said:

 

You would need to check your specifics but heat pump cylinders need to be heated with lower temperature water.  You need to heat the cylinder quite quickly as the heating to the house is off whilst the cylinder is being heated.  So heat pump cylinders typically have longer coils with a larger surface area.  

This is interesting.  So from a financial point of view, so far the following:

1. The install differential between LPG and ASHP doesn't seem as large as first thought. Looking at that quoted price difference of 11k vs 14k, that 3k difference could be more than compensated for by a 5k Boiler Grant.
2. Future proofing a LPG gas install to ASHP might require additional future costs of £2k (1k for cylinder swap, 1k to buy the LPG tank - even if we left it in the ground)
3. Rising fuel costs - LPG price could rise and Electricity prices could fall if green tariffs removed

It does push the needle a little more toward ASHP.  Out of interest, we're doing traditional construction (brick and block with 100mm full fill cavity and 150mm floor insulation with UFH).  I assume from previous comments this isn't 'the best' for ASHP, but does anyone have any general guidance on recommended insulation levels? Its a 2.5 storey house with second storey in attic space, almost a perfect square footprint.

[joth]

30 minutes ago, SBMS said:

Out of interest, we're doing traditional construction (brick and block with 100mm full fill cavity and 150mm floor insulation with UFH).  I assume from previous comments this isn't 'the best' for ASHP, but does anyone have any general guidance on recommended insulation levels? 

That's just meeting building regs levels isn't it? Generally around here when people say "we are building well insulated" it means at least 50% more. 150mm walls is common for many builds here, and 200mm+ under floor.

Also, you need a specify an airtightness goal. Building regs is 5 ACH (lower is better) but most folks here wouldn't consider anything above 2 to be that well built.

 

 

Edited December 21, 2021 by joth

[joth]

By the way, if you've not seen it many have found Jeremy's heat loss calc to be very useful to get an idea of payback for  improvements in insulation and airtightness :

 

 

[IanR]

1 hour ago, SBMS said:

The current draft regulations seems to specifically include self build properties, see regulation 7 in the DES’ draft legislation for the boiler upgrade scheme:

 

Requirements for new-build properties
7. A property meets the requirements in this regulation where—
(a) any building that forms part of that property was built principally with the use of the labour or resources of the first owner (including where the resource was a loan which the first owner was liable to repay), and
(b) the property has not, while the building was built or at any subsequent time been owned wholly or partly by a person who is not an individual.

 

 

That's really good news. Seems the Boiler Upgrade Scheme will be extended to include to include self-builds, as per RHI.

 

It's the logical step to ensure self-builds continue to consider ASHPs up to 2025, when they will be forced to.

 

Assuming the BUS legislation retains this once it gets on to the statute books, then for this scenario ASHP seems a "no brainer". The £5K grant should more than cover any additional cost in installing an ASHP.

The Building Regs changes for next year require a "low temp" (under 55°C flow temp) heating systems, so I assume that will bake in a Hot Water cylinder into the install costs for any system in a new build and swing the needle in favour of UFH. The £5K grant only then needs to cover the difference in cost of LPG/Oil Boiler + tank with the cost of an ASHP.

 

A benefit of ASHP and UFH is that it can also bring some active cooling to the house, assuming the BUS rules will allow ASHPs to cool, as they do under RHI with the revised rules.

 

3 hours ago, SBMS said:

In all likelihood I would suspect levies are focused on mains gas; LPG makes up such a tiny fraction of usage in the UK - and bearing in mind off grid properties are already limited in energy choice, I think it will be targeted last.

 

I don't believe this is correct, off-gas-grid fossil fuel boilers are already in the sights of the Government to be tackled first. As well as banning their replacement from 2026 I'm sure they will pull on all the levers they can to persuade owners to move over to ASHPs.

[J1mbo]

3 hours ago, SBMS said:

for a well insulated, new build is there a compelling reason that I’ve missed to go with ASHP over LPG. 

 

ASHP doesn't run out of gas.

[ReedRichards]

1 hour ago, SBMS said:

...I assume from previous comments this isn't 'the best' for ASHP, but does anyone have any general guidance on recommended insulation levels? 

 

This isn't an ASHP issue.  The less insulation you have the greater your heat loss.  The greater your heat loss the higher your running costs and the greater the output capacity you need from your heat source.  

[Thedreamer]

A self build constructed to a good standard needs very little heating. 

 

Eliminate the need for space heating and you just need hot water. We run our hot water from exhaust air source heat pump, cheap capital cost and cheap running costs. Our total electricity consumption is 10-11 units a day for a family of four.

 

I use a centrally placed wood burning stove to provide a boost in the evening. This winter, I'm burning sticks I collected in the summer, my space heating are £0.

 

A unique set-up for us and probably not for you, but my suggestion is to build your system around the availability of local resources, your skills/experience and budget.

[SteamyTea]

1 hour ago, SBMS said:

brick and block with 100mm full fill cavity and 150mm floor insulation with UFH

Brick and block is another term for leaky.

Not everyone agrees, but I would put more insulation in the floor. The U-Value may look impressive, but the UFH means the temperature difference is higher, si overall losses are higher. It is losses that are trying to be reduced after all.

[joth]

19 minutes ago, ReedRichards said:

 

This isn't an ASHP issue.  The less insulation you have the greater your heat loss.  The greater your heat loss the higher your running costs and the greater the output capacity you need from your heat source.  

It's slightly an ASHP issue: ASHP are *much* more efficient if operating longer periods at a lower temperature.  Low and slow.  If your house construction and usage pattern is "let the house get really cold when no one is home, then BLAST the heating at industrial furnace levels when we get home" you're less likely to be satisfied with ASHP.

(But to be fair, anyone going for all UFH in a slab will find this to be true regardless of heat source)

 

 

[joe90]

4 minutes ago, SteamyTea said:

Brick and block is another term for leaky.

not if it’s built properly, parged inner walls and attention to detail of junctions. Mine is brick and block and got a fairly good airtightness result, since then I have improved the few “leaks” found during the test (and @SteamyTea was here).

[SteamyTea]

4 minutes ago, joe90 said:

not if it’s built properly, parged inner walls and attention to detail of junctions.

That is the problem though.  It needs extra work done to it.

And who knows the long term performance as few people will ever get a second air test as it costs £250.

[joe90]

3 minutes ago, SteamyTea said:

That is the problem though.  It needs extra work done to it.

And who knows the long term performance as few people will ever get a second air test as it costs £250.

The extra work is no more (in my opinion) than that done with any other build type. I am not convinced on the longevity of glue used fir membranes and tapes which can be pierced so easily. With parged walls and full wet plaster, which is the only issue with brick and block minimal work and cost are involved.

[SteamyTea]

Just now, joe90 said:

minimal work and cost are involved

Totally reliant on the workers though.

I am not saying that any other type does not suffer from bad work, but factory built is better than onsite built by design, why it is done that way.

 

Ideally the @50Pa test would be 2 not 10, and a £100k cash back insurance if it fails a retest after a decade.

[joe90]

4 minutes ago, SteamyTea said:

Totally reliant on the workers though.

Most of us are self builders and if like myself keep a wary eye on all work done (or do it ourselves) I would agree that factory built is better but that limits it to kit houses which arrive as panels, then you have to manage the way the panels are assembled on site which cannot happen in the factory.

[SteamyTea]

3 minutes ago, joe90 said:

Most of us are self builders

yes, and if I was building, I would take time off work and spend it all with tapes, tars, adhesives, rolls of membrane, GRP and a home made tester.

I am surprised that the volume manufactures don't have the kits available and test places as they go.

£5k of kits, £35 k/year to employ someone.  1000 houses and the cost is £40/house.

160 kWh of electricity.

[dpmiller]

volume producers don't want airtight tho, as this forces extra expense on the ventilation side

[Christiano]

3 hours ago, SBMS said:

Good point regarding the tank removal charge - especially if we are sinking it. Would likely have to buy it off the provider. I would provision for a system LPG boiler with an unvented cylinder so that at a later date only the heat source (boiler) were switched out. Would a cylinder for a gas boiler be compatible with an ASHP or would that need replacing too?

 

Calor want £295 + vat to take our tank away. We don’t get anything back for the 11-1200l of LPG inside it either; we didn’t decide on the heat pump until after they topped us up in the spring.

 

We had an unvented cylinder installed in 2017 so we could use PV diversion to heat it via Solar iBoost and immersions. Our installer got a custom build cylinder with 3 coils in case we got a heat pump; good call!

Edited December 21, 2021 by Christiano

[saveasteading]

57 minutes ago, joe90 said:

longevity of glue used fir membranes and tapes

At leak susceptible junctions such as sole plate to footing or slab, I am wondering what seals are going to last long-term.

There is mastic tape that stays flexible indefinitely as long as it is free from light, but that is for installing within the interface of metal sheets, not for sealing gaps.

I think anything from a tube will eventually harden or shrink.

Off the wall perhaps, but what about denso tape ? Does that last for ever or do bugs eat the Vaseline?

[saveasteading]

32 minutes ago, dpmiller said:

volume producers don't want airtight tho, as this forces extra expense on the ventilation side

I don't think the majority of major developers understand the construction process well enough to have decided this.

 

Anyway, the tests and BCO inspections do not include ventilation, which is approved in desktop assessment, not in site tests.

I am certain though that the housing units for test are decided and agreed in good time to ensure a pass, while the rest are left leaky.

 

Then there is the quality and control process itself. I know a council who only gave planning approval on condition of a change of Architect and their own BCO having access throughout. This to ensure passable housing standards after previous experience......It is not possible to find info on the estate they disliked so much.