Real-World Heat Pump Running Costs

Solar PV is a Necessary Enabler of the Transition to Electric Heating 

Much of the discussion of the transition to electric heating has focussed on the installation costs of heat pumps, but what do the running costs look like?  It’s all very well handing out £5,000 grants to make heat pump installations more affordable for consumers, but if people take this government incentive only to discover that the cost of energy bills become cripplingly expensive, the resulting negative coverage could stop the transition to clean heating before it gets going.  Conversely, if energy bills fall for houses with heat pumps, it will make it much easier to convince people to ditch their gas boilers.  To get a sense of costs, we need to know two things - how much does electricity cost compared to gas and what efficiency can we expect from heat pumps and gas boilers.

How Much do Heat Pumps Cost to Run?

Advocates of heat pumps regularly claim that a ‘well designed, well installed and properly run heat pump will cost no more to run than a gas boiler’.  A careful re-reading of this sentence will show you that three things have to go right for heat pumps to cost no more than gas heating. 

One thing we know for sure is that in the UK electricity costs much, much more per unit than mains gas.  Nottingham Energy Partnership has the average standard rate for electricity in September 2021 at 23.3p/kWh (kilowatt-hour), and mains gas at 4.39p/kWh.

The efficiency of a modern condensing gas boiler is often said to be around 90%, but since we are interested in real-world heat pump performance, we should compare like for like.  A field trial of the seasonal efficiency of 60 boilers by the Energy Saving Trust in 2009 gave a value of 82.5% for combi boilers.  

Using this efficiency one unit of gas heating costs 4.39/0.825 = 5.32p/kWh.

For heat pump heating bills to cost no more than a gas boiler, the efficiency of the heat pump would need to be higher than 100% x 23.3/5.32 = 438%, but what efficiency do heat pumps achieve in practice?

Real World Heat Pump Performance

The Energy Savings Trust and the Department of Energy and Climate Change (now called BEIS), set out to answer this question in 2008.  The first large-scale heat pump field trial in the UK aimed to determine how heat pumps perform in real-life conditions. The year-long field trial monitored technical performance and customer behaviour observed at 83 domestic properties across the UK.

The resulting report (Getting Warmer: a field trial of heat pumps), published in 2010, found that the average efficiency for an Air Source Heat Pump (ASHP) was 220% (page 16), although this was revised down to 182% by a subsequent analysis published in 2012.  This second report corrected errors and removed data provided  by ‘Manufacturer A’ which were felt to be from systems that had been hand-picked, carefully optimised and installed in the homes of the manufacturer's own staff.  (See Detailed analysis from the first phase of the Energy Saving Trust’s heat pump field trial, pages 19-25)

Note: I have focussed only on Air Source Heat Pumps because most people expect that this is the technology that will be deployed in the greatest number.  They are lower cost and more convenient to install than more efficient Ground Source Heat Pumps which require a deep bore hole to be drilled or trenches to be dug.

Image: System Efficiencies of Air Source Heat Pumps reported in “Detailed analysis from the first phase of the Energy Saving Trust’s heat pump field trial”

Despite the best efforts of the authors to put a gloss on things (“the best performing systems show that well-designed and installed heat pumps can operate well in the UK”), the results were highly disappointing.  

Real-World Heat Pump Performance - Try Again

The UK heat pump industry responded positively to the issues identified in the trial and significant changes were made to the regulatory scheme for UK heat pump installers. The Microgeneration Certification Scheme (MCS) rewrote its MIS3005 installation standard for heat pumps to better control the quality of system design, installation practices and householder training that had been shown to affect heat pump performance.

Consequently, a second phase of the study was initiated.  38 of the heat pumps in the first trial were selected for interventions to improve their performance. Interventions ranged from major (swapping an over or under-sized heat pump), medium (changing radiators, adding a buffer tank, replacing circulating pumps with variable speed DC pumps) or minor (changes to controls, refilling the ground loop, adding insulation). Householders also received improved guidance on how to operate the heat pumps properly.  Six new heat pump systems installed to the new MCS standard were added to the sample and all were monitored from April 2011 to March 2012.

The results for the second attempt were published in a summary and detailed form:

the heat is on: phase 2 heat pump field trial

Detailed analysis from the second phase of the Energy Saving Trust’s heat pump field trial

As a result of all these interventions, the average efficiency of ASHPs in the new study rose to 245% 

Note: this performance improvement Phase 2 and Phase 1 included a change of the definition of efficiency – on a like for like basis the increase was from 183% to 211%.  However the preferred efficiency measure in Phase 2 (SPF H4) is in my opinion a better comparator with boiler efficiency than the System Efficiency measure used in Phase 1.  System Efficiency includes losses between hot water tank and taps/showers, whereas the SPFH4 boundary stops at the hot water tank.   

 

Real World Heat Pump Performance - Third Time Lucky? 

In March 2017 UCL Energy Institute published its Final Report on Analysis of Heat Pump Data from the Renewable Heat Premium Payment (RHPP) Scheme.

Around 14,000 Heat Pumps were installed with funding from the RHPP, and 700 of these (around 5% of the total) were subject to a detailed monitoring study.  The study reports an average efficiency based on SPFH4 for the ASHP in the sample of 241%. 

However it also reveals that the heat meters used in the study were calibrated for water and not the antifreeze-mix with which most would be installed .  The estimated 4-7% over-statement of performance was not corrected in the published result.  Applying a mid-range 5% correction, would make the true average SPFH4 nearer 229%.

Reassuringly, this is still closer to the second EST study than the first and suggests that the changes made to the industry standards in response to the disappointing performance of systems in the first study had fed through into a higher general performance, across a reassuringly large sample of installations.

Taking efficiency from this most recent study of 229%, the annual energy costs for a house heated by a heat pump will be (23.3/5.32) x (100/229) = 1.91 times higher than the same house heated by a gas boiler.

So, even after industry steps to eliminate design errors, carefully optimising the installation and coaching the householder how to use the heat pumps, running costs are still double those of a gas heated property. 

What hope do we have when we scale up to install heat pumps in the huge numbers envisaged by UK policy makers?  If installations increase from 30,000 a year currently to the 300,000 a year called for by the government will the heat pumps perform as well as those in the second study, or is it more realistic to anticipate performance closer to the first study?

Adjusting the Price of Gas & Electricity

One approach to make heat pumps more appealing is to make gas more expensive and electricity cheaper.  Government indicated in its recently published Heat in Buildings Strategy that it would consider this approach:

“we will look at options to shift or rebalance energy levies (such as the Renewables Obligation and Feed-in-Tariffs) and obligations (such as the Energy Company Obligation) away from electricity to gas over this decade” Heat in Buildings Strategy p16.

What impact might this have?  According to OFGEM  Environmental and Social Obligation Costs at 25% of the price of electricity, whereas it’s only 2.5% of the price of gas.

Infographic Bills, prices and profits, 27 Oct 2021, Source OFGEM

The cost of a unit of electricity might come down to 75% x 23.3p = 17.5p/kWh

By how much would gas need to increase to replace the lost revenue?  Again, according to OFGEM typical dual fuel domestic consumption values as of 1st April 2020 were: 12,000kWh for gas and 2,900kWh for electricity.  (Source - see footnote)

For an annual use of 2,900kWh for electricity, the social tariffs come to 25% x 2,900 x £0.233 = £169

For a gas use of 12,000kWh to replace this social levy, the price of gas would have to rise by £169/12,000 = 1.4p per kWh, taking the price of a unit of gas heating after boiler efficiency up to 6.72p/kWh

If this were to happen, we can adjust our calculation for the difference in running costs 

Under this scenario, an ASHP might have running costs (17.5/6.72) x (100/229) = 1.14 times higher than gas heating, but only in 10 years’ time as government makes clear that any transition would have to be gradual to avoid pushing people into fuel poverty.

Heat Pumps and Solar are a Perfect Combination

Even when heat pumps are ‘well installed and properly operated’, even by taking 25% off the cost of electricity and shifting it over to gas, it seems likely that consumers are going to be paying more for the shift to electric heating long after the bill for the installation cost has been settled.

For an average dual fuel bill with 12,000kWh of gas use at 4.39p/kWh, the heating cost is £527/year.  Taking the ASHP efficiency from the most recent study, with ASHP heating bills 1.91 times higher than gas, the extra cost to the householder is £479/year.

One way to make the transition to zero carbon heating cost neutral on running costs is to insulate the property and reduce its heat demand.  If heat demand could be halved, running costs would end up at the same level.  However, this might be a tall order for households that have already taken the basic steps of loft and cavity insulation and double glazing, and also taking into account that the hot water demand cannot be insulated away.

If a 3kWp solar system is installed with the heat pump, generating say 2,550 kWh a year of electricity, and if 50% of that generated electricity is used on site to offset electricity use at 23.3p/kWh (£297) and 50% is exported to the grid under the Smart Export Guarantee at 5p/kWh (£64) then we’ve saved the resident £361 a year from their energy bill.  If we combine this with battery energy storage and push the self-consumption of solar electricity up to 80%, then the corresponding saving becomes £500 a year.

The solar doesn’t need to be generating at the same time the heat pump is operating for the savings to be there – remember that any electricity use in the property can be offset (for example appliances, heating hot water and even charging electric vehicles), and every unit not bought from the grid is a saving on that household’s electricity bill.

Social Landlords, housebuilders and policy makers facing the challenge of how we are going to get our homes to zero carbon while bringing tenants, homebuyers and voters along for the ride need to start thinking of solar PV and other smart energy technologies as enabling technologies for zero carbon heating.  Otherwise the real-world running costs for heat pumps could prove to be an inconvenient barrier to mainstream adoption of electric heating.

Updates: 

2.12.21 - it was pointed out to me that the original version of this blog used gas boiler efficiencies of 90% (which are representative of laboratory test) and unfairly compared these with actual performance in the field for heat pumps.  The blog was updated to use field test results of combi-boilers from Final Report: In-situ monitoring of efficiencies of condensing boilers and use of secondary heating, 2009 The Energy Saving Trust, with annual efficiency of boilers re-set to 82.5% instead.

Do We Need to Talk About Fugitive Emissions from Heat Pumps?

 Could the Benefits of Future Building Standards be Affected?

It’s not a recent study, but its contents may have become newly relevant.  In March 2014, the then Department for Energy and Climate Change (DECC) published the results of a study commissioned from Eunomia Research and London Southbank University - “Impacts of Leakage from Refrigerants in Heat Pumps”.  

Governments are looking for a huge increase in the number of heat pump installations in an attempt to decarbonize the heating of buildings.  Leading the charge will be developers of new homes, since these are the easiest to legislate for.  The UK government has unveiled its Future Homes Standard and Scottish Government is consulting on a New Build Heat Standard.  Neither of these regulations would force developers to install heat pumps in the homes they build, but the standards will be set in such a way that fossil-fuel powered boilers will not comply - the clear intention is to use regulation of the new-build sector to scale-up the heat pump industry.

The approach being considered by Scottish Government is to require heating systems to emit no carbon dioxide at the point of use.  Technologies considered to meet this requirement are direct electric heating (panel heaters, underfloor electric, electric boilers), heat pumps and also heat networks (where you could be burning coal at the far end of the pipe but this doesn't count as point of use).

But since the goal of all of this is to reduce global warming, then surely the emissions of other gases that cause global warming should also be considered.  It turns out that the refrigerant gases used inside some heat pumps are greenhouse gases that are thousands of times more powerful than carbon dioxide.  So long as they stay safely inside the heat pump during its life and are collected up at end of life, there is no problem, but the question the report set out to answer was how much of this refrigerant gas is lost to leaks, and how big an issue could that be?

The researchers examined the logbooks of heat pumps to see how often they had to be re-charged with refrigerant, and also conducted experiments where heat pumps were emptied and then recharged with refrigerant gases and the amount lost in the process was measured.

How Much Refrigerant is Lost?

The report found that:

• 10% of domestic heat pumps experience a leak of refrigerant in any given year
• The median amount lost was 35% of  charge (the total refrigerant gas in the system)
• So the equivalent annual leakage rate was 3.48% of the charge
• The mean refrigerant charge for a domestic heat pump was 3.3kg
• So the mean annual leakage for a domestic heat pump is 0.114kg of refrigerant
• Decommissioning losses at end of life were 15% of charge 
• Commissioning and recharging losses were around 0.06kg

So if we assume a 20 year life for the heat pump, a charge at commissioning, one recharge and decommissioning at the end of life then the total losses are:

Filling: 0.06kg 

Recharge: 0.06kg

Leakage: 10% x 35% x 3.3kg x 20 years = 2.31kg

Decommissioning: 15% x 3.3kg = 0.495kg

Total Refrigerant Losses over 20 year life: 2.925kg

Refrigerant loss per year: 0.146kg

Does it Matter?

At the time of the report, R410A was the most used refrigerant.   It has a Global Warming Potential (or GWP) of 2,088, which means that 1kg of R410A released into the atmosphere has the same effect on global warming as if 2.088 tonnes of carbon dioxide were emitted.

So, a refrigerant leakage of 0.146kg per year from a heat pump is like it emitted 305kg of CO2 per year.  This is expressed as 305kgCO2e (CO2 equivalent)

The authors of the report compared the impact of refrigerant leakage to the benefits of the low-carbon energy delivered by the heat pump.  The annual heating load for a domestic property was assumed to be between 10 and 25 thousand kWh and it was concluded that the impact of leakages was small. 

 

However, the leakage losses from the heat pump does not vary with the amount of heat it supplies.  The more heat the heat pump delivers, the less of a penalty the refrigerant leakage is per unit of heat delivered.  Conversely the more energy efficient is the building and the lower its heat demand, the more of a penalty the leakage becomes per unit of heat.

Since the regulations are aimed at new homes, perhaps we should instead consider refrigerant emissions in relation to the heat demand of these.

Homes that are built today have very much higher levels of airtightness and insulation than the average building stock.  Based on energy calculations we see in our design team, an average sized new build house (say 85m2 total floor area) will have space heating demand around 3,300kWh per year to which you can add 1,600kWh per year for domestic hot water.  The proposed standards envisage tightening rules on insulation too, so by then buildings will have an even higher level of thermal efficiency than this.

Many houses are now being built to ‘passivhaus’ standards which remain at a comfortable temperature most of the year without heating, so the annual heating demand approaches a minimum which is that needed for hot water for showers and baths.

If we divide our 305kgCO2e figure by these lower figures for annual energy demand, the contribution to global warming per unit of heat delivered looks very different.

Table 1: Release of refrigerant gases per  kWh heat delivered (CO2e)

Annual Heating Budget (kWh)	2,000	3,000	5,000	10,000	25,000	Gas Heating CO2 emissions for comparison
Annual Emissions from Refrigerant Leakage per kWh of heat delivered (kgCO2e)	0.152	0.102	0.061	0.031	0.012	0.208

 

The table shows the global warming impact of refrigerant leakage for each unit of heat provided by a heat pump running R410A for different levels of annual heat demand.

It can be seen that for buildings with high heating demand (such as the levels assumed by the report authors), the CO2e figure is very low compared to delivering the same heat with gas heating.  However for very highly energy efficient properties the penalty from the refrigerant leakage rates is very significant – approaching that of gas heating.

Current Refrigerants in Use

Of course, we would expect heat pump technology to have moved on in the last six years and with regulations aiming to phase out the use of the refrigerants with the highest GWP, maybe R410A is no longer in use?

I did a quick straw-poll of the products available today from a range of heat pump manufacturers.  As you can see from the table below, there are clearly now models available that work with refrigerant with much lower GWP than the R410A used in the calculation above.  Notable leaders are products from Vaillant using R290 (which is propane gas and has a GWP of 3) and from Mitsubishi using R744 (which is carbon dioxide and so has GWP 1) - although both these manufacturers still offer models with the much higher GWP refrigerant for some reason, perhaps cost or efficiency?

It is also clear that there are also many, many models still being sold today that are using refrigerants with GWP above 1,000 and that R410A is still very popular.

 

Company	Model	Refrigerant	GWP	Source
Daikin	Altherma 3 H HT - EPRA014-018DW	R32	675	https://www.daikin.co.uk/en_gb/products/epra014-018dw.html
Daikin	Altherma 3 R - ERGA04-08EVA	R32	675	https://www.daikin.co.uk/en_gb/products/erga04-08eva.html
Daikin	Daikin Altherma - EDLQ-CV3	R410A	2,088	https://www.daikin.eu/en_us/products/edlq-cv3.html
Daikin	Altherma R - ERLQ-CV3	R410A	2,088	https://www.daikin.eu/en_us/products/erlq-cv3.html
Kensa	Shoebox	R134A	1,430	https://uh8ex3jph2xqg0pb4bs7if12-wpengine.netdna-ssl.com/wp-content/uploads/2014/03/TI-Shoebox-heat-pump-v6.3.pdf
Kensa	Evo	R407C	1,774	https://uh8ex3jph2xqg0pb4bs7if12-wpengine.netdna-ssl.com/wp-content/uploads/2017/02/TI-EVO-v6.0.pdf
Mitsubishi	Ecodan R744	R744	1	https://les.mitsubishielectric.co.uk/products/heating/domestic/outdoor/ecodan-quhz-monobloc-air-source-heat-pump
Mitsubishi	Ecodan R32	R32	675	https://les.mitsubishielectric.co.uk/products/heating/domestic/outdoor/ecodan-r32-ultra-quiet-puz-monobloc-air-source-heat-pump
Mitsubishi	Ecodan R410A	R410A	2,088	https://les.mitsubishielectric.co.uk/products/heating/domestic/outdoor/ecodan-puhz-ultra-quiet-monobloc-air-source-heat-pump
Panasonic	Aquarea HT Bi-bloc F Generation	R407C	1,774	https://www.aircon.panasonic.eu/GB_en/product/aquarea-f-generation-ht-bi-bloc-single-phase-three-phase-heating-only-shf/
Panasonic	Aquarea T-CAP Bi-bloc H Generation	R410A	2,088	https://www.aircon.panasonic.eu/GB_en/ranges/aquarea/t-cap/
Panasonic	Aquarea High Performance All in One Compact J Generation	R32	675	https://www.aircon.panasonic.eu/GB_en/product/aquarea-high-performance-all-in-one-compact-j-generation-1-phase-r32/
Vaillant	Arotherm plus	R290	3	https://www.vaillant.co.uk/downloads/aproducts/renewables-1/arotherm-plus/arotherm-plus-spec-sheet-1892564.pdf
Valillant	Arotherm Split	R410A	2,088	https://www.vaillant.co.uk/for-installers/products/arotherm-split-heat-pump-58752.html
Valillant	Arotherm	R410A	2,088	https://www.vaillant.co.uk/for-installers/products/arotherm-air-source-heat-pump-2944.html

 

Conclusions

Based on the report, it appears to me that the level of “Fugitive emissions” from heat pumps is significant enough that heat pumps with refrigerant of high GWP  should not be considered as zero carbon (equivalent) at the point of use.  

This is especially the case when the heat pump is providing heat to a highly energy efficient new building and the emissions ‘cost’ is spread over a much smaller heat ‘benefit’.

Perhaps legislators should consider the global warming potential of refrigerant in heating systems when they create new building standards?  Since heat pump models are available with improved refrigerants, perhaps they should consider applying a ceiling GWP value to the refrigerant in use?

I would be interested to hear from colleagues in the heat pump industry about whether this issue has been much discussed, and what the future direction of travel in heat pump technology is to address the likelihood or impact of leakage of refrigerant - please comment below!

The Domestic RHI and Solar Thermal Stores

The Law of Unintended Consequences Strikes Again

The domestic RHI was structured with the intent that the complementary combination of solar thermal with other heating technologies would be actively encouraged by receiving double subsidy for the domestic hot water energy.  Unfortunately, the wording of the legislation has prevented installers using the simplest way to implement a combined system (the thermal store) because it rules out solar systems that can make even a theoretical contribution to space heating.

Thermal Stores in Hot Water

Solar thermal systems can make a contribution to space heating as well as domestic hot water (DHW) preparation, especially in spring and autumn where the days are still bright and there is a demand for space heating.  These systems are not yet as common in the UK as those for domestic hot water, but in more developed European markets such as Germany and Austria, so-called "solar combi systems" are popular.

In a thermal store the domestic hot water is heated in a heat exchanger
and the contents of the store pumped around the space heating circuit

A good way to combine solar thermal with space heating is to use a thermal store, essentially a large (typically 500 litre minimum to 1,000 litre) hot water cylinder with heat inputs from both solar and the backup heating system and with outputs to domestic hot water and space heating.  Typically the body of water in the thermal store is heating system fluid (primary water) and domestic hot water is heated on-demand in a heat exchanger as it flows to the hot tap.

Both heat pumps and biomass heaters operate well when running continuously rather than cycling on and off, so charging a thermal store is a good technical solution that improves the overall efficiency of the heat pump or biomass boiler.

Where the designer is seeking for the solar to make a reasonable contribution to the space heating, the solar panel array installed is large (around 12-18 m² for a domestic property).   The coverage of domestic hot water of such systems can be very high, 70% and above.

Where the designer is aiming for solar to mainly cover domestic hot water the panel array is smaller (typically in the range of 3  - 6 m²).  In this case there is still a theoretical possibility that the solar energy will contribute to the space heating, though in practice the system is sized with the aim of supplying 60-70% of water heating.

The current domestic RHI legislation completely excludes systems that can contribute towards space heating.  

The text in the RHI regulations defines an eligible solar system as follows:

a)     is designed and installed to provide heating solely to a single eligible property and solely for an eligible purpose using liquid as a medium for delivering that heat;

(b) meets the requirements set out in whichever of the standards for solar thermal plants specified in paragraph 1(5)(a) and (b)“eligible purpose” means, in relation to heat generated by— […](b) a solar thermal plant, the purpose of domestic hot water heating for an eligible property;

An implementation of solar where there is even a theoretical possibility of the solar contributing towards space heating is completely excluded from the scheme.

The reasoning behind ruling out solar space heating was that the domestic RHI is “deemed” – the solar energy is not measured, instead it is estimated using an approved calculation and the calculation only works for domestic hot water.

However, by ruling out any solar installation that does not solely heat domestic hot water, the domestic RHI has made the combination of complementary renewable heating technologies such as solar and heat pumps less likely. Solar thermal has lower associated carbon emissions than any form of back up heater, so every unit of solar thermal heat that can be used, whether for space heating or domestic hot water reduces carbon emissions.

Configurations where the solar is offsetting a proportion of fossil fuel space heating are also disincentivised by their complete exclusion from the domestic RHI.

When installing biomass or heat pumps with a thermal store, the additional cost to add a solar coil into the store is very low, making the marginal cost of adding solar thermal more attractive.  The domestic RHI would provide greater value for money if it encouraged, rather than discouraged such systems.

So how could the domestic RHI be changed to include solar space heating?

Two Suggestions

Two options occur, though I’d be pleased to hear of any other suggestions (please use the comments section).

First, it would clearly be possible to use a heat meter to measure the solar input into the thermal store.  Solar space heating systems cost more than solar systems aimed only at domestic hot water.  A requirement to fit a heat meter would be a relatively smaller proportion of the total installed cost and energy benefits, and houses that can fit large thermal stores are relatively thin on the ground, so it wouldn’t be too much of a cost for the scheme administrators to deal with the meter readings.

A second approach would be to allow space heating systems onto the scheme but to give RHI payments only for the domestic hot water energy provided, and calculate this with the current deeming method.  I’ve looked at this with the help of two years'  of data from a solar space heating system provided by Geoff Miller of GreenLincs Energy.  Simulations have also confirmed that the solar energy generated by a system providing solar space heating and domestic hot water is always higher than the same sized system targeted at only domestic hot water.  The RHI wouldn't be over-paying for solar heat.

The best outcome would be for it to be the choice of the homeowner whether or not to go to the expense and hassle of having a heat meter.  If they wanted the extra payments for space heating, then they would need to install a heat meter, otherwise they could claim for only the solar heat in their domestic hot water.

This has formed the basis of a proposal submitted to the Department of Energy and Climate Change (DECC) yesterday outlining how the scheme could be improved by allowing solar space heating.

Heat and Power

Early signs of a rebalancing of the renewables market

The Microgeneration Certification Scheme (MCS) November newsletter was recently released, and a graph caught the eye of the solarblogger.  It is reproduced below.

The total number of MCS registered installers has been falling for some time.  Companies registered to install photovoltaic (PV) solar technologies dominate the numbers, and since the painful tariff adjustments of 2011, the number of registered companies has been steadily falling.  In the last 12 months the number of solar PV installers has fallen from around 4,300 to around 3,000.

Two features of the scheme may mean that even these figures are an over-statement of the number of active PV installation businesses.

First, since businesses renew annually with the scheme, a company decision to exit a market can take some time to feed through into the figures.  Falling registration figures will trail by an average of six months.

Second, renewal is significantly less expensive than a new registration with the scheme.  This asymmetry causes business to retain their MCS registration even when they are not actively working in the market “just in case things pick up.” 

Industry colleagues estimate that around 10-25% of MCS registered PV installers are not actively selling solar PV.

But none of this is news.

The thing that really jumped off the page for the solarblogger was that while the registered PV installer numbers have continued to fall, the total has actually risen since August 2013. 

There has been an increase in the number of businesses registering to install heating technologies such as biomass, heat pumps and solar thermal. 

Details of the domestic Renewable Heat Incentive (RHI) were announced in July 2013.  This scheme pays households that install heat-generating renewable technology and will go some way towards rebalancing the UK government’s lopsided support for renewables.  A successful domestic RHI alongside a stable Feed in Tariff could deliver long term growth for both renewable heat and electricity.

It seems like industry might just be starting to believe in the RHI.