How to decide between ASHP or Gas boiler for New Build

[JohnMo]

We have 3.1 kW PV, offsets electric costs, diverter, supplies most of the DHW in the summer

[Dillsue]

On 05/08/2022 at 10:42, Meabh said:

How do we decide?  I always thought we'd just go the green route with the ASHP but now we aren't so sure?

 

Lots of options already offered but something worth considering is your proximity to civilisation and likelyhood of extended power cuts. In the past weve been without electricity for 3 days over xmas so we would never rely on a full electric heating solution such HP. We currently heat with WBS and an LPG boiler as backup. DHW is from solar thermal with top up from the WBS in the winter. A small genny runs any or all of those if the power goes off which is typically a couple of days a year.

 

If we go to a HP in the future it will be in addition to the WBS and bolier.

 

If you include a large buffer now youll be able to have both gas and ASHP if youre happy to have 2 x standing charges. If youre even a touch remote get your spark to put in generator changeover switch and buy a small genny

[m0deller]

If you're designing for the future go ASHP. Expect gas to get more expensive relative to electricity in the longer term. It's also really cool heating your house off solar on a bright and cold winters day. I'd also put in as much PV as possible. 

[Hodgey]

Hi, I thought this might be a good place to piggy back my conundrum rather than starting a new thread. I'm replacing an oil based central heating system in a 1985 built bungalow with a 120m2 floor area and I'm struggling to decide between ASHP or getting mains gas + boiler. 

 

Connection to mains gas has been quoted at £3K, add on @ £3k - 3.5K for a decent boiler installed = £6.5k.

 

So I'm considering ASHP as the future proof option plus the £5K BUS contribution might leave a few quid for a log burner to compensate in winter (I have read the complaints about ASHPs in winter, justifiable or not). We want to upgrade the existing single radiators anyway so that's not factored into costs. 

 

I'm really struggling to find any credible advice about ASHP's that isn't linked to recommeding installers so am feeling a bit dubious about the whole industry and thinking it might just be easier to connect to the gas, so I'd be really interested to hear from anyone what they would do in my situation. 

 

As we have just bought the house we have no historical data but the EPC says:

Estimated energy used to heat this property

Type of heating	Estimated energy used
Space heating	14288 kWh per year
Water heating	2368 kWh per year

Edited September 1, 2022 by Hodgey

[JohnMo]

Basics what is your heat demand and flow temperature to the UFH?

[Marvin]

14 minutes ago, Hodgey said:

Hi, I thought this might be a good place to piggy back my conundrum rather than starting a new thread. I'm replacing an oil based central heating system in a 1985 built bungalow with a 120m2 floor area and I'm struggling to decide between ASHP or getting mains gas + boiler. 

 

Connection to mains gas has been quoted at £3K, add on @ £3k - 3.5K for a decent boiler installed = £6.5k.

 

So I'm considering ASHP as the future proof option plus the £5K BUS contribution might leave a few quid for a log burner to compensate in winter (I have read the complaints about ASHPs in winter, justifiable or not). We want to upgrade the existing single radiators anyway so that's not factored into costs. 

 

I'm really struggling to find any credible advice about ASHP's that isn't linked to recommeding installers so am feeling a bit dubious about the whole industry and thinking it might just be easier to connect to the gas, so I'd be really interested to hear from anyone what they would do in my situation. 

 

As we have just bought the house we have no historical data but the EPC says:

Estimated energy used to heat this property

Type of heating	Estimated energy used
Space heating	14288 kWh per year
Water heating	2368 kWh per year

It worth considering all the AIM and APE elements before making decisions. That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

Some of these will not work properly without the others:

 

1. A MVHR will not work properly without Airtightness.
2. An Air Source Heat Pump will have to compensate for the lack of Airtightness and Insulation to the degree that the benefits become questionable, especially during winter, without them.
3. An ASHP uses electricity and Photovoltaics can supply a little during winter and a lot during summer when cooling can be a problem and an ASHP can supply cooling.
4. PV can supply a little to an Electric Vehicle during winter and plenty during summer if your vehicle is at home during sunny days.
5. Extending a property and only doing AIM works to the extension will be no good, you have to do all the property within the thermal envelope. 

So if finances cause you to have to consider only a few in my humble opinion AIM first and go APE later. (but prepare the property for the APE works as much as you can).

 

Best of Luck

 

Marvin

[Hodgey]

Thanks very much Marvin you've given me some useful ideas there. 

 

I know nothing about MHVR so will find out more, sounds like it would be good for the bungalow as I understand they can suffer from condensation anyway. We were planning to get trickle vents in the new windows but maybe this could be a better alternative. 

 

We are replacing windows and doors so that will help the airtightness, the insulation seems to be pretty good and can be improved if necessary.

 

The oil tank and boiler are coming out as they take up a 10' x 6' chunk of space that will become an office so I need to decide on its replacement asap. The E can wait.

[ProDave]

On 06/08/2022 at 13:35, PhilT said:

so my installation net cost has doubled (c. £6k to £12k).

I still struggle to see where these costs come from?  ASHP easily bought for £5K,  it took me 2 days to wire one and the plumber about 2 days to plumb it a few weeks back.  I really wish between us we could have been paid £6K to install it.

[Dreadnaught]

Don't count on spending that £5k from the BUS. An ASHP install that would cost £6,000 will magically cost £11,000 under the bus ("there is so much paperwork don't you know"). I am buying the ASHP myself and will use a local air-conditioning engineer to install, 1- or 2-days work max.

 

No BUS for me.

[Nick Laslett]

11 hours ago, Dreadnaught said:

Don't count on spending that £5k from the BUS. An ASHP install that would cost £6,000 will magically cost £11,000 under the bus ("there is so much paperwork don't you know"). I am buying the ASHP myself and will use a local air-conditioning engineer to install, 1- or 2-days work max.

 

No BUS for me.

Will the engineer sign-off on MCS for the ASHP install? I don’t know if it is of any significance, but the SAP calculation for an ASHP is different if it is not an MCS compliant install. I can’t remember how many points it knocks off. *(Edit) If the characteristics of an ASHP are in the SAP product database, these efficiency values will be used. 

https://www.ncm-pcdb.org.uk/sap/searchpod.jsp?id=17

 

 

Edited September 2, 2022 by Nick Laslett

[ProDave]

15 minutes ago, Nick Laslett said:

Looks like they are still trying to find ways to claim the very much more expensive MCS install is "better"

[Dreadnaught]

Thanks Nick.

 

27 minutes ago, Nick Laslett said:

Will the engineer sign-off on MCS for the ASHP install?

 

No. I won't be asking for this.

 

I wonder if the Arotherm Plus ASHP will be available in the "Products Characteristics Database" for SAP. Does anybody know?

I've emailed my SAP assessor to ask.

 

32 minutes ago, Nick Laslett said:

If the characteristics of an ASHP are in the SAP product database, these efficiency values will be used. 

 

Did you mean "aren't" rather rather than "are"?

[Dreadnaught]

@Nick Laslett,  I just heard back from my SAP assessor. He said "Yes, the arotherm products are on the PCDB so we will use this data within the assessment".  

 

Edit to add: when I also asked whether MCS certification (or its absence) will affect the SAP result in any way, he said: "We do get an option to tick "MCS certified" but it does not affect the results in any way."

 

So I think I am doubly content with that.

Edited September 2, 2022 by Dreadnaught

[PhilT]

18 hours ago, ProDave said:

I still struggle to see where these costs come from?  ASHP easily bought for £5K,  it took me 2 days to wire one and the plumber about 2 days to plumb it a few weeks back.  I really wish between us we could have been paid £6K to install it.

Appreciate the possibilities if you are able to do/manage everything yourself. Although my house is a self build I'm now too old unfortunately so this is a 3rd party commercial installation of ASHP, new HP compatible DHW tank, header tanks, six new radiators, all plumbing, controls and electricals and took 2 guys a whole week to install. £15k gross less £9k RHI grant.

[Nick Laslett]

6 hours ago, Dreadnaught said:

@Nick Laslett,  I just heard back from my SAP assessor. He said "Yes, the arotherm products are on the PCDB so we will use this data within the assessment".  

 

Edit to add: when I also asked whether MCS certification (or its absence) will affect the SAP result in any way, he said: "We do get an option to tick "MCS certified" but it does not affect the results in any way."

 

So I think I am doubly content with that.

Your assessor is correct. I just checked with the Stroma SAP software. If you use the PCDB entry the SAP result is not effected by the MCS tick box. If you use the default SAP values for a generic ASHP, then the MSC tick box does improve the values.

 

Back when I originally played about with the software, I just used the generic ASHP entry, this is because the software lists the PCDB category as "boiler", which confused me at the time.

[Simon R]

On 05/08/2022 at 10:42, Meabh said:

We ran the PHPP software out of interest and got 

 - Specific space heating demand 29 kWh/m2
 - Maximum heating load 15 W/m2

 

The SAP passes with

 - ASHP

 - Gas boiler with 4.5kWp of PV (we have a south facing roof that I've always planned to have PV on anyway)

I'm a bit late to this thread, but noticed no mention of solar gain. The effects of solar gain in a very well insulated structure comes as a bit of a surprise and has caught out several build hub members.

Our ICF build came out with a figure of 68W per degree difference. In practice we think this is more like 80w but still incredibly low by normal standards, too low to make an ASHP financially sensible. So we have a small gas combi boiler which got us through the winter very comfortably. On sunny days we seldom had any heating requirement.

Spring however was rather different and our east facing glazing started to cook us.

We now have two split aircon units, one 3.5kW and one 2.5kW which we run very happily from a 4kW PV system. The two units from Midea cost £1800 installed and now we have very comfortable house, one runs the open plan living area and the smaller one our bedroom. We havn't been through a winter with them installed yet to experiment using them for heating.

Looking at your idea to 'zone' areas you may find that a number of small aircon units may be a flexible and cost effective option.

[Hodgey]

On 01/09/2022 at 13:26, Hodgey said:

Hi, I thought this might be a good place to piggy back my conundrum rather than starting a new thread. I'm replacing an oil based central heating system in a 1985 built bungalow with a 120m2 floor area and I'm struggling to decide between ASHP or getting mains gas + boiler. 

 

Connection to mains gas has been quoted at £3K, add on @ £3k - 3.5K for a decent boiler installed = £6.5k.

 

So I'm considering ASHP as the future proof option plus the £5K BUS contribution might leave a few quid for a log burner to compensate in winter (I have read the complaints about ASHPs in winter, justifiable or not). We want to upgrade the existing single radiators anyway so that's not factored into costs. 

 

I'm really struggling to find any credible advice about ASHP's that isn't linked to recommeding installers so am feeling a bit dubious about the whole industry and thinking it might just be easier to connect to the gas, so I'd be really interested to hear from anyone what they would do in my situation. 

Update! ...Had three estimates for the ASHP which I can share for anyone else looking at this, two came in at £15k and one at nearly £22k. So, no heat pump for me as it's not viable. Gas it is then! Maybe I'll get a pump when the industry establishes itself better (in @ 10 years?). 

[markc]

20 minutes ago, Hodgey said:

Update! ...Had three estimates for the ASHP which I can share for anyone else looking at this, two came in at £15k and one at nearly £22k. So, no heat pump for me as it's not viable. Gas it is then! Maybe I'll get a pump when the industry establishes itself better (in @ 10 years?). 

ASHP are not a simple “do I replace my gas/oil boiler for a ashp”? Question.

in a new build it is much easier but changing over is going to cost more (and even more if you want a grant towards it)

[Rich210]

That's amazing prices, I think the up tick is due to the market instability and lack of government over the last month or so. I'm currently working towards making my house suitable for ASHP. Ideally I see solar PV and ASHP being the future for my property. We shall see!

[PhilT]

On 09/09/2022 at 10:14, Hodgey said:

Update! ...Had three estimates for the ASHP which I can share for anyone else looking at this, two came in at £15k and one at nearly £22k. So, no heat pump for me as it's not viable. Gas it is then! Maybe I'll get a pump when the industry establishes itself better (in @ 10 years?). 

Have you investigated the new Octopus heat pump offering? https://octopus.energy/get-a-heat-pump/?gclid=CjwKCAjwsfuYBhAZEiwA5a6CDMKI6dOagklOak9qTEMtWeoIzdw5SEUNo2MX8s0XkWoGUGdiK9bCGRoCFrsQAvD_BwE

[Cleighton]

I looked into this myself 4 years ago trying to future proof my self build. Having spoken to countless people at self build shows I ended up with gas. 

I have installed a baxi eco blu 30kw heat only boiler, 300l unvented cylinder, 4.8kw solar edge PV with optimizers, Beam MVHR and a solic 200. I over sized the radiators in case i changed to ASHP in the future, however, the heating upstairs is not used its just to warm. Wet underfloor downstairs is rarely used, I also bought a Scan 58-6 log burner which is an expensive ornament at the moment, it has not been fitted with a flue and I will probably sell it as it is not needed.

 

As some have mentioned solar gain is often missed and underestimated, I will probably fit a canopy blind or air con. My kitchen diner has 2- 3m sets of bifolds and a further 2- 1m floor to ceiling glass panels! This is my first self build and was a huge learning curve, would I change anything? Probably more PV and batteries which I am considering.

 

Solic 200 is worth its weight in genuine gold, it supplies nearly all my hot water for 2/3 of the year, Boiler comes on for 45 minutes in the morning, only because my wife likes a scolding shower before work !!!! and that's only when she is working early.

 

MVHR is probably the best investment with the insulation in my circumstances.

4 years on, I am doing the same for my daughter, who is building next to me. In the current fuel climate, I still cannot justify the cost of an ASHP if the investment is put into the fibre first.

At the time of writing, these are the temperatures in the house.

I am still new to self building, but have been in the trade for years and these are just my personal experiences and opinions.

[SteamyTea]

Similar to mine.

This is for all of September so far.

 

[Hodgey]

On 12/09/2022 at 17:04, PhilT said:

Have you investigated the new Octopus heat pump offering? https://octopus.energy/get-a-heat-pump/?gclid=CjwKCAjwsfuYBhAZEiwA5a6CDMKI6dOagklOak9qTEMtWeoIzdw5SEUNo2MX8s0XkWoGUGdiK9bCGRoCFrsQAvD_BwE

I have PhilT, made an enquiry on their website about 5 weeks ago, all good for location etc. someone will be in touch soon etc. heard nothing. We're connection to the mains gas!

[Hodgey]

On 12/09/2022 at 17:04, PhilT said:

Have you investigated the new Octopus heat pump offering? https://octopus.energy/get-a-heat-pump/?gclid=CjwKCAjwsfuYBhAZEiwA5a6CDMKI6dOagklOak9qTEMtWeoIzdw5SEUNo2MX8s0XkWoGUGdiK9bCGRoCFrsQAvD_BwE

By the way, still heard nothing from Octopus 😞

Edited December 16, 2022 by Hodgey

[PhilT]

5 minutes ago, Hodgey said:

By the way, still heard nothing from Octopus 😞

They are probably too busy managing their tariff schemes, "saving sessions" and the traffic from Bulb (hope they haven't wasted their time!)