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Renewable Heating Incentive Page


This is the blog for webcentral's new Green heating installation and follows the process of installing a renewable heating system that will hopefully be effective, simple to use and economic to run as well as being "Green".



Background to Renewable Heat Incentive


The Renewable Heat Incentive, which is due to start in spring 2014 [now] has been a long time coming, it was originally proposed in 2009 to compensate early adopters of green heating systems for the extra cost of the equipment involved in converting to renewable heat sources such as Biomass boilers, Heat Pumps and Solar Thermal hot water systems. Like the Feed in Tariff for Solar PV, users would be paid quarterly for the amount of renewable heat used for 20 years. The original rates quoted seemed extremely generous like the initial FIT rates for Solar PV. The rates have been watered down and the complexity of the scheme has increased, but the final scheme which has now actually started since I started writing this page looks like it will reimburse the difference in cost between say, a new oil central heating system and an air source heat pump or biomass boiler.


The scheme started on 9/4/14, but eligible systems that were installed by MCS registered installers since July 2009 will be able to claim the payments.


The scheme is based on the deemed heat required to heat a building based on the figure given on an EPC that has to be carried out along with a Green Deal Assessment. The idea being that the payments will not pay to waste heat, which may happen if the heat produced were actually measured.


Full details of the scheme are available here;


But the rates at launch are as below ;



Biomass boilers and biomass stoves

Air source heat pumps

Ground source heat pumps

Solar thermal

Tariff (per kilowatt hour renewable heat)





In my case, I discounted biomass systems as they require storage space for the wood pellets and the boiler needs to be fed with the pellets and the system regularly cleaned, which I felt was a backward step from our existing oil boiler, which although expensive to run was easy to use, just needing oil 2 or 3 times a year and the occasional service.


The Solar Thermal option is purely for Hot water rather than central heating, although can be used in conjunction with the other renewable sources.


That left Heat pumps, both Air Source and Ground Source. My preferred choice was Ground Source, but as we don't have a huge flat garden to dig several hundred meters of trenches for a ground loops, it meant drilling several hundreds of meters of borehole downwards. Due to our geological location and lack of anybody willing to quote for drilling boreholes it was decided that it was to be an Air Source Heat Pump System.


To be honest my main reason for changing to a renewable heating system is the high cost of heating using oil, rather than great environmental concerns, although these are still significant. The RHI should help with the installation cost, which seem a lot higher and not just because the equipment is more expensive. Some might say that the existence of the RHI has increased both the technical requirements, but also the administration and hence the installation cost. However, if the scheme suceeds like the Feed In Tariff for Solar PV, it should both increase the knowledgebase of competent installers and eventually reduce the costs as the systems become more popular.


How Does an Air Source Heat Pump Work - The Technical bit!!


Basically an ASHP is an airconditioning unit running in reverse, so the unit draws in air from the surroundings, passes this over a heat exchanger which boils a refrigerant by extracting heat from the air. The refrgerant, imaginativley called R410A, is a very cold liquid when under pressure at about -40C, so even air at -20C is a lot hotter and can turn it into a gas. When this gas is compressed to turn it back into a liquid it gets hot and its this heat which is transferred into the water that runs around the radiators that heat the house.


Many people say how can you heat your house by the cold air outside. You have to think of a fridge, that extracts heat from inside, and shoves it out the back via a radiator. So the cold inside is equivalent to the cold outside air and the radiator at the back is effectively the radiators inside the house - Simples, just a lot bigger!!


So why is it "Renewable" and/or "Green" - Because the heat that ends up heating the house is basically transferred from the ambient surrounding air into the house. The energy used to transfer the heat is not renewable admittedly and this is not paid for by the RHI, but this energy is approx 20-50% of the total. This means instead of our old oil boilers approx 70% efficiency the heat pump is between 200% and 500% efficient. Basically for every unit of energy put in to power the HP, you get between 2 and 5 units out as usable heat.


The wide variation in efficiency quoted above is dependent on two main variables, namely, the outside air temperature and the temperature of the water circulating round the radiators. The colder the outside air and the higher the inside radiator temperature, the harder the HP has to work reducing the efficiency and costing more to run. So when its very cold outside, you want hot radiators the electricity cost to power the heat pump is probably more than the oil boiler, but in spring and autumn when you still need heat, but its not quite so cold the system is much cheaper to run than even Gas. Overall, taking the year as a whole, the system should still be cheaper to run than oil - We Hope!!


The outside air temp is controlled by the weather and we do live in a particularly mild microclimate here in St lawrence, but the temperature of the water flowing through the heating system is something that can be reduced by careful design and its here that its most important to have an installer who understands the fundamental point that the water temp must be as low as possble, but still high enough to heat the house. 


Getting Green Deal Assessment and an EPC


Before claiming the RHI, you need to have the property assessed for its heating requirement, this means paying about £100 for a Green Deal Assessment which includes an Energy Performance Certificate. I rang up one of the few on the Island and they came round to inspect the property and ascertain how we use it. You also must have at least 250mm of loft insulation and Cavity Wall insulation if applicable and the assessment will confirm these so that you can claim the RHI. The idea being that its pointless spending £1,000's on a new "Green" system if all the heat escapes out the roof or walls.

After a month or two we received the EPC which confirmed the loft and wall insulation and gave an annual heat requirement of 22,000kWh, which includes about 2,000kWh for hot water.

As at 20/5/14 we still have not received the Green deal assessment, apparently the assessors are still having difficulties gaining the correct registrations. It may have to be done again!! I stupidly said in November when the assessor came there was no hurry, but 6 months later its becoming a concern, we will need it to apply for the RHI.


Any way the EPC figure means that the RHI will be about £1000 per year for 7 Years, which should pay for about 60% of the total system. There should also be a saving of £5-900 a year on the annual fuel bill. We currently use about 2000-3000Litres of Oil a year which costs about £1750 although last year [2012-13]was more like £2000 as the price of oil was higher and it was a very long cold heating season.





Getting Quotes


So I set about getting quotes, I looked up the MCS register to see who on the Island was qualified to install these things and so be able to claim the RHI payments. There were only about 5 or 6. I asked 4 of them to quote me for a Ground Source Heat pump, the first two came round and after much discussion on our lack of flat ground and sharp intake of breath when I mentioned boreholes, both said I would be better with either a biomass boiler or an air source heat pump, I pointed out I didn't want to go down the biomass route as I had several reservations. They went away and after being chased up one quoted me £12,000 for a biomass boiler and no mention of heat pumps. The other one who had said I wouldn't want a Ground Source Heat Pump as the system would cost £20-30,000, proceeded to quote £27,000 for a biomass boiler. When I asked both of them about the heat pumps they waffled on about how much more RHI I would be able to claim with a biomass system, ignoring my reservations.

The second 2 installers were warned beforehand that I didn't want biomass and after a couple of weeks received quotes for air source heat pumps. Malcolm McClellan from Go-Eco finally explained why getting quotes for a Ground Source Heat Pump with boreholes was so difficult, basically drilling boreholes, especially round here is risky, and almost impossible to quote for. The drillers may hit hard rock - more expensive or they may hit soft ground - more expensive or they may hit water - you guessed it, more expensive. The problem with ground water is that it can often be under pressure and can gush out of the borehole and be almost impossible to stop. The final nail in the coffin was that the drilling companies will never give a fixed price and also point out that they will not be liable for any damage they may cause, basically you pay £1000's a day to drill or rectify problems. The recent Undercliff Drive repair problems that Island Roads have had with ground water have underlined the problems of dealing with nature's forces. 


I now had two similar quotes for Air Source Heat Pumps, both around £9-10,000 for the main heating system and a new Unvented Hot water system, but both plus £2-3000 for necessary changes to the existing radiator system, which although OK for a high temperature system like our Oil boiler or even a biomass boiler, not for the lower temperature output from an ASHP. One quoted for all the radiators to be roughly doubled in size, the other quoted for some of the rads to be replaced with Dimplex Smartrads, which are basically radiators with built in fans. These would be smaller in size to our existing ones but would be much more efficient with the lower water temperatures. They would reuse the larger existing rads in rooms that had smaller ones. This quote also specified the Panasonic 12kW T-Cap ASHP which unusually for a heat pump maintains its heat output at outside temps down to -20C, most drop in heat output when temps go below +2C, just when you need it!!


So after years of waiting for the RHI to start and months of getting quotes we decided to go with Malcolm McClellan's Go-Eco Consultancy [Gec-Co Heat pumps]. He and his head heating engineer both live on the Island, although the office is in Southampton. Malcolm also installed the Air Source Heat Pump in the village hall about 10 years ago and has done a few systems in and around the village. We also spoke to another customer of a similar system in Whitwell who was very pleased with their work and more importantly the Panasonic T-Cap air source heat pump. I was also impressed with how quiet it was when running, much quieter than our oil boiler.


Siting of the Heat Pump


The planning of the installation really started some months back, when the decision was made as to where the heat pump and ancillary tanks  would be sited. The existing oil boiler, which will have to be decommissioned, is situated in a boiler room outhouse a few feet away from the main house, but due to proximity to the boundary this was unsuitable for the ASHP, this being a condition of permitted development. The area underneath our front decking beside the garage was chosen for the HP, the various tanks and plant being in the rear of the underground garage. The advantages being the short pipe runs to the plantroom and the more central position of the hot water cylinder, which should reduce the rather long wait for hot water to arrive and the most used taps in the kitchen and the main ensuite.


The area was cleared of several years worth of old plant pots etc. and Kevin the heating engineer made a concrete base and sculptured the area to give good airflow to and from the HP.

The installation is scheduled to take about 14 days and starts in ernest on 21/5/14, the concrete base being laid about 2 weeks earlier.


Some electrical and plumbing works prior to main delivery.

                                                              The heat pump certainly comes in an impressive box!!




 The Hot water cylinder and the buffer tank with some pipework, its beginning to look like a power station with all the plumbing!!




 The ASHP in its final resting place under the decking, the hot water cylinders being directly behind it, in the garage, in this photo - It certainly took some ingenuity getting there, it had to be winched up a ramp over the steps. 


 The finished plumbing with the insulation fitted.


5/6/14 - Heat Pump Installed and switched on for testing with existing radiators. Smartrads to be installed next week. Solar Immersion also fitted by Sean the Electrician today. The heat pump and the solar powered immersion combined heated the 210L hot water tank from cold to 60C in about 2hrs using about 4.5kWh of electricity, only 0.4kWh of which was imported, the solar PV provided the rest "Free". That total also includes heating the 90L buffer tank from cold to about 38C.


Meter Readings

HP 5.61kWh

Rate 1 13353 Day

Rate 2 11474 Night

Total 24834 kWh


The initial impression of the heating system was disappointing with the existing radiators, this is probably due to several reasons, but mostly because the system needs rebalancing as the feed from the HP is entering the radiator circuit at the opposite end of the house and the flow temp is very low as there is little need for heat at the current outside air temperature. The HP's weather compensation reduces the flow temp to 38C when the outside air temp is above 13C, which it is at the moment. Hopefully things will improve once the new Smartrads are installed and the system is rebalanced next week.


The main problem turned out to be the thermostat, we have a Honeywell CM927 "smart" thermostat, which unfortunately is too smart for the heat pump, it was cycling the HP on and off 6 times an hour which is exactly what a HP dislikes. The HP takes 10 mins to get going by which time the thermostat decided to switch it off. There is a setting to reduce it to 3 cycles per hour, giving a 20min cycle, which is still going to confuse the HP, but setting this helped the system heat up. The "TPI Cycling" only occurs when the actual room temp is within 1.5 Degrees of the set temp in an attempt to even out the room temperature. A quick call to Honeywell the manufacturer of the thermostat confirmed that none of their programmable stats are suitable for Heat Pumps, due to the "TPI" control which for some unaccountable reason cannot be completely disabled.


Luckily Kevin had a non smart wireless programmable thermostat in the van, a Salus RT500RF, which their technical dept. confirmed would not try and be too clever for the HP. The wiring diagram in the installation manual however seems to have a printing error, so after much head scratching a wiring link was added and all seems to be working. The system now remains on long enough for the rads to get warm, with no unwanted intervention from the thermostat.


We have had a few delays with Bank Holidays etc, but the Smartrads have now arrived, so the system has been turned off and drained down for the changes to the emmitter system.


The Smartrads are going in, Kevin is making an excellent job of changing the pipe layout from the conventional rads to the much smaller Smartrads. Not helped by our wooden floors which we obviously don't want to lift. Some of the bigger radiators are being reused in the smaller rooms where they will be more than adequate with the lower flow temps from the HP.


We had another visit today from the Green Deal Assessor, it seems their acreditation has now come through. We were reassessed for the GDA, but the EPC he carried out in November is still valid as the new system is not in operation yet. Hopefully we will get all the Green Deal paperwork early next week, ready for the de-commissioning of the old oil boiler and the commissioning of the new Air Source Heat Pump. We will then need to get an MCS certificate from Gec-Co and enter the our details and certificate numbers onto Ofgem's RHI website to register the system and claim the RHI. 


The above shows Kevin, concealling some pipework behind a skirting board, so that the final job, below, looks as neat and tidy as it could possibly be, considering the contraints of not being able to lift the wooden floors to change the plumbing. - A craftsman at work!!


The above is a Smartrad 180, which is 90cm wide, but has the heating capacity of a normal radiator 3 or 4 times its size, even at the lower flow temperature from the heat pump. Our system will run a variable flow temperature of between 35C and 45C dependant of the outside temperature, the heat pump's weather compensation automatically decreases the flow temperature as the outside temperature rises to increase efficiency and further reduce costs.


All the Smartrads are now in and the larger old rads moved to the smaller rooms, so all there is to do is a final connection of the new emmitter circuit that replaced some old 8mm copper piping that was never very good. Then its a case of finalising the wiring for the Smartrads, they need an electrical supply to power the fan and built in temperature controls, before refilling the system and balancing the emmitter system.


18/6/14 - Final day of Installation - Kevin connected the whole system up, carefully filled the system/radiators and after much bleeding off air from the system and wiring up the Smartrads, he then turned on the Heat Pump.  Hey presto!! everything worked, its a shame its so hot at the moment we can't properly test the system, but Kevin and Malcolm assure us we will be positively "Toasty".


First impressions of the Smartrads is they are very quiet, you have to listen very carefully to even tell the fan is on when on the normal speed. The Panasonic heat pump itself is also very quiet, even when trying out the system today, running full blast, with the windows wide open and 24C inside you had to put your head out of the window to even hear it at all!!


 Its typical that just when you want it to be cold, you get a heat wave, not something you expect in June!! - We will just have to be patient and wait for autumn before we can try out the system fully. Meanwhile the heat pump will top up the solarimmersion if we get a few dull days in a row. The oil boiler is now decommissioned and disconnected - no more oil deliveries!! - Does anyone need a 1800L plastic oil tank and or a Worcester Bosch 18-25 Combi boiler - full working order - very cheap to run!!! ;o)



For those interested in the Solarimmersion which diverts any excess solar PV generated electricity directly to the immersion heater in the hot water tank, I will post more details on the Solar PV blog on the Green page here - [Scroll to the bottom of the page].


The RHI Application


Following the commissioning, Malcolm from Go Eco emailed through the MCS Certificate Number and I eventually received the Green Deal Advice Report from the Island assessors who have eventually received their accreditation, I had the EPC in February, so I now had everything I needed to claim the RHI.

Unlike the Feed In Tariff for Solar PV, things have moved on and the RHI application is an instant online web form on the Ofgem site. This looked to be a big improvement, I thought, but after a few minutes filling in address, bank details,  the MCS,EPC and GDAR certificate numbers plus a few optional details about the system I was ready to press the APPLY button. After a few seconds it came back that the application needed to be checked manually and I would be contacted in a few days.  I rang the helpline, who were surprisingly helpful, they said my identity had to be confirmed and I would be contacted for more details - So not as efficient as I had thought!!


After a couple of days, Ofgem emailed, asking for copies of Driving Licence and Bank Statements for identity verification, which I sent by post and after a few more days they emailed again to say the application had succeeded and that the quarterly payments would commence on 27/9/14 for 7 years. - So not too bad after all, much better than the Solar PV Feed In Tariff application which took about 4 months to process!!


So we will receive £265.32 a quarter until next April when that will increase by inflation based on the RPI for each year for 7 years. This should total about £7428.96 plus inflation, which along with any fuel bill savings should pay for the system in about 7 years assuming no massive electricity bills or maintenance costs. I will report on monthly electricity usage and costs on here and the Solar PV Statistics Page.


The System in Use


The first few weeks since installation have been remarkably uneventful, the SolarImmersion has been quietly diverting any excess generation into the Hot Water tank and by about lunchtime each day we have had a full tank of 69C hot water, which is still 67C at bedtime and still well over 40C the next morning after our showers etc. So long as the tank temperature is above 37C the heat pump doesn't need to kick in and so far the temp has not dropped below 40C for over a month since the SolarImmersion was fitted. This means we have had completely free hot water so far even on cloudy days of which, admittedly, there have been very few. The true test will start in autumn, I don't expect it will do much in Mid Winter, the HP will probably kick in most days to keep the hot water above 37C, but the SolarImmersion will still contribute on all but the dullest winter days. Our PV export has reduced from about 70% to about 45% in June as we are now using much more of our generation ourselves, but because the FIT payments for export are based on a deemed 50% export there is no change in the actual payments at all. Because we are no longer paying for oil for the boiler to heat the hot water, I estimate the total fuel bill should drop by at least £200 a year, roughly the cost of the SolarImmersion!! 



5/6/15 - 1 Year Old Today - Fantastic, Can't Praise it Enough!!


Basically it just works, the house has been just as warm if not warmer, the hot water is normally a lot warmer. The system has performed just how it was predicted only a lot cheaper than predicted - see electricity costs below. Once installed and the radiators balanced and the thermostat programmer set, there has been nothing to do. The outside unit is much quieter than the old oil boiler, you cannot hear it inside at all even on the quietest night, whereas you could always hear the oil boiler firing up - no smell either!!

Outside you can hear it when its running - it sounds like big freezer, but with a big cold draught coming out of it. The outside unit does frost up on cold mornings, but it just defrosts itself, this caused a slight annoyance one morning when it decided to defrost just when it decided to reheat the hot water, but it had not got the room temp up, so it was cold for about an hour while it sorted itself out. It only happened once, and was probably an odd collection of circumstances which it was not programmed top cope with.


$60,000 question, would I do it again??, very easy answer - YES, without hesitation.


Would I recommend an Air Source Heat Pump to others - Maybe?? - The installation process is quite long, especially if radiators need to be changed, but in retrospect I don't think we needed to change as many as we did. Our system is extremely economical, but I do think it would still be viable with the old radiator system, just not as efficient. Whether the extra cost of the upgraded radiator system will ever pay for itself in extra efficiency is open to question, but you wouldn't get the £7500 RHI grant over 7 years if you didn't, so the point is moot. However a simple non RHI applicable ASHP conversion would be an awful lot cheaper and easier to install - even DIY?? The Heat Pump itself costs about £5000 in our case, if you already had a suitable hot water tank [which we didn't], and it was a simple boiler to HP swop I reckon it could be done for about £7500 or less with some DIY. That would be about £5000 cheaper than we spent, but we have got a more economical system with a new hot water system and are claiming the £7500 RHI, plus saving about £1000 over our previous Oil bill. All in all, our system should fully pay for itself in 5-7 years easily assuming no major breakdown expenses - as ASHP's are regarded as having a 15-25 year life with very low annual maintenance I am fairly confident in that guesstimate!! 



Meter readings


HP = 4639.30kWh Used by Heat Pump in the year

Solar Immersion = 1546.63kWh Solar PV diverted to the Immersion in the year

Rate 1 = 16885kWh Day Rate

Rate 2 = 14779kWh Night Rate

Total = 31672kWh = 6838kWh  Electricity used in the year by whole house in the year


At an average of 11p per Kwh for electricity our total electricity bill including the Heat Pump was £752.18 whereas the year before the HP it was £336.00, so the Heat Pump has cost £416.18 for the whole year in electricity which compares very favourably with the cost of 2-3000L of oil - Normally about £1500 - £2000 a year. It was a fairly mild winter and the price of oil has reduced, but a saving in excess of £1000 in the first year

is fantastic!! Plus £1061.28 back from HM Govt. in RHI payments [£265.32 a quarter].


Aha you say, but you have 4Kw of Solar PV on your roof and that reduces the running cost of the HP. True, but not by as much as I expected, the simple fact is the sun rarely shines when the HP is actually on. Most electrical consumption by the HP is early in the morning and later in the evening exactly when the solar PV isn't generating much. At a guess I would say the Solar PV saves about £100 a year in HP electricity for central heating. The saving by the Solarimmersion for Hot water production could be as much as £200 a year. So perhaps £300 a year cheaper because of the Solar PV in total - pretty useful saving, but still much cheaper than the oil.


The combination of Solar PV, Solarimmersion and Air Source Heat Pump is certainly to be recommended - they are all viable and pay for themselves individually with the help of Govt. grants but as installation drop [Which is the whole point of the Grants] these systems become economically viable without any govt. intervention. In our case we now have a heating, hot water and electricity system which is very environmentally friendly and efficient, that produces an TAX FREE INCOME of over £3000 a year [FIT and RHI]  with only about £750 of yearly expenses. This contrasts to our pre Green days of nearly £2500 in energy expenditure [£2000 oil and £500 Electric Bills]. So we are better off by about £4750 a year, by installing the Green Stuff!!


Aha you say again, but if you left the money you spent on the installation in savings, you would have had an income or capital growth from that!!  - True but where would you get a consistent  guaranteed 10% income. The closest type of investment I can think of to this is an annuity because in general annuities don't give your capital back. Currently a £28,000 annuity will give an guaranteed income of about £600 a year - just over 2%pa if your lucky.


Aha, you exclaim, but what if you move!! - You got me there. Some would say it will add value to the property, but I cannot wholeheartedly say any of these installations will add any value to the value of the house. It should attract buyers because of the low running cost/income, but I can't see many people paying more for the property, some may even be put off, by those hideous, noisy green contraptions!! 


 31/12/2015 - 1st Full Calender Year

The Heat Pump has used 4326.28kWh of electricity in its first full calender year, which is in line with the estimate earlier in the year - About £400. Again a very mild winter so far, but still very economical. Oil is currently £395 for a 1000L [BoilerJuice quote today for PO38], which is about half the price of two years ago, so in year with a mild winter I would probably have used about 1500L, so about £600. If oil stays as low as this the HP will be cheaper, but will not pay for itself in savings in the 7 years I estimated. Time will tell if the figures add up, but if oil stays this low or goes even lower and the winters are mild, then the HP savings could take 30 years to cover the cost of the installation, even with the 7 years RHI payments. If someone asked me now if I would install a HP, I would still do it myself, but could not in all honesty say its economically a good idea with oil at its current price, unless you need to change the oil boiler anyway. Having the Solar PV also adds to the savings, on top of those stated above and may knock a few years off the payback time, but its very difficult to put a figure on it.