Boiler Upgrade Scheme (UK) - £5k grant revoked

There are loads of fables around about why asph’s won’t work.

I was terribly annoyed with installers telling me that it was not possible so I rang an asph company, two weeks later the install was done. Energy costs dropped on average by Euro 100 / month. This is using old fashioned radiators - which in time will be replaced by low temperature radiators.

In case its freezing, we do have a wood fuelled fireplace which is our backup if needed.

House is almost 100 years old.


Ah, so you live in a “new” house. :grinning:



Good to know Phil.
Our house was built by Bovis, so the Lord only knows how well the plumbing was done. I have no idea how long the microbore pipe runs are, only that we were rejected by Octopus Energy as unsuitable for an air sourced heat pump due to this piping. Perhaps there needs to be a clearer standard on what is & isn’t okay?

Best regards, BF

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Hi BF,

IMV, step 1 when contemplating an ASHP is to have your existing installation surveyed by someone without a vested interest. The history of CH installations differs so much, often dependent on the plumber/installer preferences, what kit (e.g. boiler) was installed and the method of construction of the house e.g.

– having had 2 full gas CH systems installed in different houses in 1996 (1930’s build) and 2004 (c.1968 build), both times the same installer used 22m feeds to/from boiler, with step-downs to 15mm for the flow/returns. Much of the pipework is hidden and skilfully installed with drops in room corners etc, covered by boxing.

IIRC, micro-bore was favoured in the 1980/90s due to cost (world copper price?) and ease of installation but in the 1960/70s and even before, sometimes copper pipes were run in floors unwrapped before being covered with concrete resulting in pitting, weeping and leaks as time went by (who’d have guessed concrete (inc lime) would react with bare copper!). There’s also the issue that concrete floors often settle, taking the pipework with them!

With so much pipework hidden I am highly resistant to power-flushing. I’d rather simply lift a few rads off and flush these out.


One test worth doing is to reduce the CH water temperature to say 40C and see what temperature the surface of the radiators reach and whether the house stays warm enough. It may take longer in the morning to reach the required room temperature and for the surface temperature to reach a maximum. You don’t want too big a drop between the boiler water temperature and maximum the radiators can reach (5C would be really good).

These observations will help you to decide whether the existing radiators need upgrading and whether there are likely to be any pipe work problems. Obviously it’s best to test in the cold weather.

It’s important to understand that the heat pump won’t produce as much hot water as a gas boiler. You could measure the gas boiler output by taking 90% of the hourly input by looking at the gas input from the smart meter.

MCS installers have to do detailed calculations in order to determine the heat needs of each room and the boiler size needed. These are for extreme conditions and can make very pessimistic assumptions of heat losses. My triple glazed windows were not properly assessed and the build standard such as Building Regs compliance virtually reduced to non standard. The worse is the assumption about air leakage. The fact that I know the gas consumption is irrelevant.

EPCs are similarly irrelevant. The whole system is disfunctional! But you won’t be cold and won’t have the most economical system to run especially if the boiler controls prevent you running the pump efficiently. That said even a COP is 3 means the heat pump is no worse than gas at the moment. However, some installers don’t care and basically don’t want to deal with complaints that the house is too cold and hide behind the high running costs that they warned you about. Somevforce you to replace perfectly good pipe work so that they can’t be sued for not reaching the MCS standards. The small firms will be forced out of business! I have take on the risk with my pipe work.



In my view the requirements for this scheme are too inflexible and badly thought out, and the 15mm pipe requirement is an example of that.

No ASHP here, but I’ve replaced all the radiators in our house, and replaced a mishmash of pipework with 15mm as it seemed like the right thing to do. The one exception is the largest radiator in the house. It has 8 metre runs of 8mm microbore, and I just couldn’t be bothered to chase out the walls and lift floorboards in an otherwise finished room, so I reconnected the new rad to the old pipes. It works fine, in fact it’s the most effective rad in the house.

I doubt the standards took into account the environmental and financial costs of ripping out and scrapping perfectly good pipe and replacing it, plus the associated chasing, replastering and redecorating.


What scheme are you referring to? I don’t think the BUS requires it, but MCS registration and rules come with extra burdens to protect the public from cowboy installers! This has the effect that there is less competition and higher prices.


I don’t remember the name of the scheme, but a friend applied for it a few months ago, and the quote included replacement of all pipes and he was told by the installer that this was non-negotiable and would be required to achieve the flow rates needed. The installer later said that they would not be able to go ahead with the installation, something to do with the costs being too high.
He’s been in touch with the local council who administer the scheme and done some digging to try to find out how it all work, and is thinking about approaching a different installer.

A key problem with all these schemes is the trust you have to put with installers or ‘experts’.
In any field there are a lot of cowboys out there…

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My installation doesn’t involve the replacement of any pipe work because I am starting from scratch with a wet system to replace electric space heaters. This makes my installation more expensive and to my mind exactly what the BUS scheme is supposed to support.

Unfortunately though, either due to ill thought out regulations or incorrect interpretation of the regulations by the administrators, my application gets revoked after installation preparations are started and I am just left to “deal with it”.

Rant over (for now). I really need to let this one go!

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Yes, it’s the installers who create the problem. I paid for a survey including an EPC . As soon as you challenge them on the survey results they insists they are right and any caveats about pipe work become demands for more money to fix the pipe work. Of course it could be the threat of loosing MCS registration.

I went to another firm who were more pragmatic and offered a simpler system with optional weather compensation which I won’t use. If the rooms don’t get warm enough I increase the water temperature or start it earlier. The lower the water temperature the higher the COP. Heating comes on an hour and a half before the alarm in the morning. You have to adjust and even wear jumpers, but it is cheaper than gas and better for the environment. It’s actually less stuffy than before.


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Did you get help for the first ASHP under the Renewable Heat Incentive scheme? Had you done the entire property in one go you would actually be better off than BUS as long as you could afford the entire up front cost.

If you didn’t use RHI I would try appealing.


We did get RHI assistance for the first ASHP, yes, but because the installation did not cover the entire property, it was restricted to a proportion of the actual use (we have a meter and are required to submit readings every month or two).

Clearly, under that legislation they foresaw the issue of part coverage of a property and put things in place accordingly.

I had thought that if I did appeal that might actually be in my favour - that I had made decisions in 2018 on the basis that assistance is available for installations covering parts of the property and that, to my mind, that assistance was reduced to reflect the fact that I could apply again down the line.

Of course, the BUS scheme is a different scheme to RHI. But maybe under some “reasonable expectation” type appeal it might carry some weight?

The scheme website and Ofgem give the rules. I seem to remember your situation being a grey area. It’s only worth appealing if you have read everything thoroughly and feel your situation is not covered by the implementation or the implementation does not correctly cover the legislation. You can’t complain that the RHI mislead you because it did not anticipate the BUS.

Hope I don’t sound supportive. Life doesn’t always work out and we wish we had made different choices. The annual BUS grants are limited so in time some people will be too late or have to delay the work. The unfortunate people are those who don’t grasp the nettle because of lack of knowledge or money. The next hurdle is the installer, and finally getting the most from the ASHP system.


At a practical level if your existing ASHP is anywhere near being rated enough for the whole house in normal winter weather I would just extend the wet system. Not sure if you have to report this to RHI. I would also spend money on improving the insulation first so the EPC rating gets up to B . Also consider solar + battery.


These boiler upgrade schemes are very hit and miss, a need to have a knackered old boiler in the right place and time where a rewarding money off scheme exists…

A few years ago 2016, had a team of Worcester Bosch affiliated engineers replaced my 19 year old oil-burner, cylinder, and nine radiators, total costing not much change from £7k

They did a good job, no complaints there but six months later had a knock on the door, a man going around the neighbourhood door to door representing the local county council asking how old the oil burner is (?) …and if it’s over 7 year old then an offer to apply for a free one… After explaining my oil burner was almost new but could i make a belated claim; he wasn’t interested and went away.

My next door neighbour, (who is rather a lot wealthier than i’ll ever be) got a free fitted WB oil burner in this deal to the tune of just under £2k saving.


Thank you for your comments Phil, much appreciated. The original ASHP is not big enough to cover the entire house, but you’re right - we might be able to squeeze a bit more out of it, especially until the RHI runs out.

We got the EPC up to a C in 2018 (from an F or G when we moved in) and we are now doing lots of more “sophisticated” insulation work now in the loft, which will also help. Original crittall single pane steel frame (massive) windows though - don’t help.

We installed an 8kW solar system and a 13kW battery earlier this year, so that all contributes.

We’re slowly pulling it into this century!

9 years ago we replaced 22 windows, one door and patio door with triple glazed power coated aluminium externally in wooden frames made by Internorm. One of the best moves ever.

I realise old Crittall windows can have a period look valued in an Art Deco context. The comfort of really good windows a big attraction though.

Our chalet is 300m2 floor area. We have a 12 kW ASHP. We only heat the upstairs at the moment. The 12kW is for really cold weather. It’s only working at 50% if that for 1.5 - 4 hours/day. It peaked yesterday at 8.6kWh for CH and DHW. The average for the last 16 complete days is 3.5kWh.

Like you I am looking at improving the roof insulation as the 10cm we put in the boarded area has slipped down so effectively there is no insulation from approximately 5’ to 7’ 6”! I learned this from an electrician who was investigating a route for a cable to the garage.


We have only had one semi serious discussion with a company about window replacement and it was going to be north of £80k, and more likely into 6 figures. I took the decision that I could buy a lot of electricity for that! I do think it would make a huge difference though. The windows are large - in quite a few of them you can comfortably stand on the sill in the window reveal. Very heavy curtains has been another “investment”.

Our house is about 325m2 with quite high ceilings and an annual electricity use of about 25000kWh. The needle hasn’t actually changed hugely on the usage since we moved in, but with all the upgrades the difference is that reasonably large parts of the house are now actually warm (rather than using all that electricity and struggling to get it above 14C in winter - not an exaggeration).

Our first ASHP is 11kW, and the second one (planned) is also 11kW. That should be enough to cover all the heating and hot water needs of the property, we’re told.

We should now also be generating between 7000 and 8000kWh useable per year via the solar/battery. That combined with the economy 7 tariff allowing us to fill the batteries off peak have done a good job on offsetting the recent hikes (at a significant up front investment cost, of course!).

All of this investment is really eating in to my Naim upgrade budget : (

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Wow, that’s a lot of electric! We started at 5,000 kWh/year plus 12,000 kWh of gas. We used 420kWh in October with the ASHP using 100kWh. It was mild. I’m trying to stay below 3,000kWh for heating and hot water!

I guess our triple glazing would cost £50k now but we paid less than half that nearly 10 years ago on a good deal.

If you haven’t already watched C4 Renovation Nation, the Cumbria one featuring Actor Ben and partner Paul started with stunning new windows being fitted to their kitchen. Worth every penny - well 3M new pennies!

Now is a turning point for building work with a recession looming. I don’t know the details of your property but a beautiful home is a wonderful thing to behold. If you can be warm as well you will be a happy person.

Good glazing captures and retains passive solar energy. For our former home I used a good small civil engineering firm who did the planning & listed building consents and the building regulations. This would allows you to get a good handle on heat requirements. You might still manage with your current ASHP, but it hardly sounds like a deal breaker to have another. What I would do is have them set up to work in tandem so the second is controlled by the primary to come on when extra heat is required.