9 Feb 2010

Thoughts on the Renewable Heat Incentive

Heat pumps
On p31 of the consultation document, it states that only efficient heat pumps will be permitted. However this ignores the fact that the efficiency of a heat pump is related to the work it is being asked to do, and not simply the manufacturing standard. The standard CoP (Coefficient of Performance - the higher the figure the better) figures used by heat pump manufacturers refer to an uplift of 35°C. For every 1°C above this that the system is required to deliver, the efficiency of the heat pump system reduces by around 3%. Therefore a heat pump may have an efficiency of 4.0 when delivering hot water at 40°C (suitable for underfloor heating) but this will reduce to less than 2.0 if used to heat radiators at over 70°C. If the published efficiency of the heat pump starts at 3.0, then the actual efficiency is likely to fall below 1.5 if used to heat conventional radiators.

A heat pump needs to perform at a CoP better than 1.5 in order to match the carbon output of an A rated oil fired boiler.

As it stands, this incentive will cause oil-fired boilers (as a technology) to be abandoned, without any clear justification. Many people with radiator-based central heating systems looking to replace a boiler will be tempted to switch to a heat pump solely because of the incentive, which looks like it's going to worth around £750-£1,000 a year for 18 years. And yet, unless the heat delivery system is changed (which is unlikely because it would be expensive and disruptive), the energy and carbon burned will actually increase, compared to an A rated oil-fired boiler. For this reason, air source heat pumps, in particular, are ill suited to replacing domestic boilers. There seems little logic in incentivising people to install them instead of efficient fossil-fuel boilers.

Bearing this in mind, why shouldn't this incentive scheme be extended into areas where it has the capability to make a much more meaningful contribution to reducing carbon emissions? How about extending it to people undertaking significant energy efficiency upgrades, way beyond topping up loft insulation and adding cavity wall insulation? The cost bringing a 20th century (or older) house up to modern standards (something akin to the Passive House standard for refurbishment, or Energy Savings Trust A rating) is far greater than the cost of installing a heat pump. Estimates vary from around £12,000 up to £40,000 (if glazing is to be included as well). The carbon savings are also much greater, however there is no financial incentive other than making savings on fuel bills. As it stands, the payback on this type of work extends to many decades.

The UK Green Building Council is putting forward a Pay As You Save Scheme, whereby lenders will be encouraged to make loans to undertake such improvements and in exchange the repayments would be paid for from the savings from lower fuel bills. Such a scheme enjoys no official backing as yet. Why not add some element of subsidy to it by adding such refurbishment to list of "technologies" which the Renewable Heat Incentive is designed to reward?


  1. £12k to £40k to uprate to near-PH standard? That can be cut to a fraction 'extra', if done as part of a reasonably ambitious extension/uprate scheme that's wanted anyway. Just a matter of arranging the building elements this way rather than that way. Same is true for all building types, commercial, industrial etc, not just homes.

  2. Tom,

    I doubt it. External insulation, rainscreen, new windows, adjusted openings and reveals, not to mention roofwork. Not cheap.

  3. I’m inclined to agree with Mark on the refurb costs – having done it myself.

    The real questions here are firstly what on earth heat pumps are doing in an incentive scheme for renewable energy. We know heat pumps use electricity, and our electricity isn’t renewable. We can work out the carbon efficiency of a heat pump. Take the new SAP2009 figure of 0.591kgCO2/kWh and a COP of 2 (the best you’d get retrofitting to radiators), net of 0.296kgCO2/kWh. Or use oil at 0.284kgCO2/kWh in a new boiler at 97% efficiency according to SEDBUK, net 0.293kgCO2/kWh. But that’s actually better than the heat pump!

    Secondly, and what is really wrong, is that this is a subsidy on energy consumption, not renewable energy generation. So you are paid by the kWh for running your heat pump, kWh as predicted by SAP – a real disincentive to improve the efficiency of your house – maybe you should rip out your existing insulation before applying, so as to reduce your SAP rating and hence increase your payments? I almost can’t believe I’ve read this consultation correctly because this is so bonkers.

  4. A modern heat pump has an efficiency of 2.5 even at minus 5 degrees ambient. If Underfloor is not appropriate then oversize your radiators to double convectors or double the size to get the flow temperatures required down. With an annualised COP of between 3.1 and 3.5 for ASHP’s which all reputable manufacturers will be able to prove in the forthcoming appendix Q for heat pumps they make a very efficient long term alternative to gas/lpg/oil boilers. Which ever way you look at it heat pumps are here to stay to reduce the long term carbon objectives by the government and dependency we have on fossil fuels. I know the argument where does electricity come from but surely we have to look beyond our current capabilities to the future proof power solutions which are predominantly going to be electric.

  5. I take it that the last comment if from a heat pump manufacturer/installer. The points made are fair enough for a new build, but the Renewable Heat Incentive is being aimed at existing properties as well as new build. In fact, arguably, because of the long tail nature of the payments, they are going to be of more interest to existing homeowners rather than new builders. Now a property owner may consider upgrading their boiler, but they are unlikely to replace their radiators as well, especially if the new ones have to be twice the size.

    Maybe the incentive should also include radiator replacement?

  6. Mark and Alan, about costs of uprate to near-PH, I agree with £12k to £40k if done as a pure uprate.

    My point is that if most of those items are about to be at least partly tinkered with
    "as part of a reasonably ambitious extension/uprate scheme that's wanted anyway"
    then the 'extra' is effectively cut to a fraction.
    I know that won't help everybody, but it's a possible strategy that should be clearly borne in mind by buildings advisors.

  7. Good information-thanks. I am keeping watch on all the latest developments in geothermal pumps-makes a lot of sense to me.

  8. 35 years ago the Atomic Energy Authority said "the future is an all electric economy" and published a scenario of electric everything by 2025.

    It hasn't happened and isn't happening much - although it's still being talked about.

    Why? Cost, resource constraints.

    Electric generating plants, transformers, wires, insulators, switchgear cost 10-100x as much as oil or gas pipes, tankers and storage tanks. These energy whole system costs are the main reason why one can fear the future
    - nothing is as cheap as oil (except some energy efficiency measures - but not Passivhaus retrofits).

    DECC should be supporting those energy efficiency and renewable energy measures which save most CO2 per £ spent. It's incredibly reluctant to do so.

    The RHI seems to be a program to pay rich people (who may live in old rectories with an oil bill of £6,000/year but can afford to spend £10,000s if they choose to do so on new kit) to make climate change worse.

    Anon says COP = 2.5 at -5 degC. What? Maybe he/she means a ground source heat pump. These may have a role.

    If it's an air source heat pump and it needs a underfloor heating system to give a COP of 2.5, then the cost of ripping-up the house and laying UFH pipes should be added to the quoted heat pump cost.

    Someone here seems to think heat pumps are geothermal. Theyre nothing to do with geothermal.

    Bath and Southampton have geotherma. It comes out of the ground at 40 or even 80 degC and it's useful as-is for heating a town or (at 40degC, as at the surface in Bath) for heating a swimming pool or public baths.

  9. We have retro-fitted a water source heat pump to a 10 year old house. We only needed to increase the size of 2 radiators, in a large room which was not adequately heated already. We used Jaga low temperature radiators, which have a small fan on top of an extensive heat exchanger so they work well with heat pumps. We don't know the COP of the system, but know our heating costs have fallen dramatically. And we live in the Scottish Borders which is a net exporter of electricity from it's wind farms. That's rather better than using the calor gas boiler we had.
    But I do see real problems with the RHI, such as people with existing systems are excluded from payments. If we extended our system to include solar panels, to cut down our carbon footprint further, we still would not receive payments, as we are not replacing a fossil fuel. And the payments are sufficiently high that people will be encouraged to remove their solar panels and re-install them later to qualify.
    I haven't seen any comments in this blog about responding to the consultation. The consultation closes on 26th April - I'd encourage you to think how it will affect you personally, and respond. I've posted some other ideas on the YouGen site - www.YouGen.co.uk
    If you can think of better ways of the Government spending their money, why not say so - with the General Election in progress we have no idea of the outcome of this consultation, and good ideas might go forward.

  10. Good post, very interesting

  11. having monitored the electric consumption of a gshp retro fitted in an old farm house over 3 years ago i can categorically state that the cop does drop but only marginally provided it has been sized and installed properly. To suggest that a heat pump will be producing over 70 degree water in radiators is ridiculous as that would require the home owners to live in their underwear. heat pumps being weather compensated deliver the heat that is required to maintain the property at the desired temp (usually 21) and because they control when deat is delivered they never need to get close to 70 degrees. have you ever held a radiator fed by a heat pump, they barely feel warm yet strangely the room feels cosy. im sorry mark but i firmly believe you are just scaremongering. anybody on here really want the truth, then contact someone directly or via an installer, who has a retro fitted hp and ask them or maybe go see for your selves. the proof is in the pudding.

  12. Reply to last post:

    Seems a tad strange to me. The point about radiators is that most systems are DESIGNED to run at 70° input, 50°C output. This has nothing to do with the heat source. If your system works well at much lower temps, all well and good: it must have been oversized by conventional standards when it was installed and it will be ideally suited to GSHP.

    But there are a great many systems that simply won't deliver the required heat unless the water temp in the rads gets to 70°C. That is the problem.