Category Archives: News & Reviews

America provides more support than UK (may do) for Solar?

By | News & Reviews | No Comments

The image of the environmentally insensitive, gas guzzling American that we in Britain like to cling to has been overturned – certainly when it comes to support for residential solar system support. If DECC goes ahead with the proposed review of the feed in tariff one could argue that Cameron’s “greenest ever” government is actually less green than the American government (one which I think it would be fair to say is not renowned for its environmentalism).

At present the American system allows for a 30%  tax credit in the first year for Solar PV systems. This in the UK would amount to a tax credit of around £2100 reduction off the cost of a £6300 residential solar system. Under our proposed scheme the UK government would offer support of (payable in year 1 of the installation – and the 30% is 100% deducted from tax – not applied at the taxpayers rate).

For a perfectly south facing, non-shaded system at the ideal roof pitch the DECC review predicts a proposed annual payment of around £ 154.19 per year for 20 years under the feed in tariff scheme paid over 20 years. One would only need to invest the tax credit into an account with a 2% savings account for at the end of 20 years for the support from the American system to be worth more than the UK system.

If you do not have the perfect roof, say have a south east roof, at a 20 degree pitch, the support in the UK falls to £143.19 per year – and all you need as an American is a 1.5% interest rate in the savings account to beat your British counterpart.

And of course – when you are buying something 30% back in the first year far beats the 30% back but dripped to you over the next 20 years! Also the American system I think is superior as it does not discourage those without the perfect roof from installing as the rebate is on the price paid and not the generated power – which also of course encourages quality (something that the UK government seem to want to drive out) as the rebate is higher for a better quality system ..

So the days of us all sniggering about the polluting, climate change denying Americans are coming to an end! They can genuinel

What will DECC’s review (if implemented) mean for the renewable energy industry?

We have been through these “mega cuts” before but what will the impact be this time around? I think that it will mean the death of the renewable energy specialist – but not necessarily for renewable energy as a whole.

The steer from DECC seems to be towards larger, industrial systems with a lot of on-site consumption being where they see PV being supported – and not in a retro-fit market on individual homes. But that has tended to be the biggest market.

Businesses often do not own the premises they are in, or have competition for resources (so a widget maker can make more money from a better, improved widget making machine than he can from PV so in a capital competition sense, PV often comes off second best!)

Homeowners love PV. It has revolutionised the way we use energy – a soft benefit over and above the electricity generated. Everyone we have installed for not only generates but makes a genuine effort to adapt their lifestyle to ensure that they use as much of the electricity as they can – and is far more aware of how much energy they use (and really does try to reduce their consumption). Simple changes – such as ensuring that our homes use more energy on sunny days (by washing the sheets and mowing the lawn when the sun shines) does I think not only have an impact on carbon reduction but an behavioural impact across our lives that helps make us all more “resource aware” ..

Lets be honest – the new rates for sub 10 kW effectively mean that the Feed in Tariff is barely worth worth applying for. Certainly costs will be higher for an accredited system – direct costs on installation – generation meter and certification – add a couple of percentage points to the installation. However indirect costs – maintaining accreditation for the installer could add just as much again – never mind the often bemoaned and expensive accreditation required specifically to access the UK market adding perhaps as much again. I would see that a non-accredited system would be perhaps at least 5% and perhaps 10% less expensive than the accredited equivalent. With the subsidy scheme returning only 30% over 20 years – a 10% reduction in the up-front costs would certainly be an attractive alternative.

The payback period is around 7.25 years. Under the new tariff 15 years. Even with a 10% fall in the equipment prices we are still over 14 years.

My assumed £6300 system consists of – 54% on panels and inverters, 12% on the railing and electrical wiring components, with 34% on roof labour, an electrician and scaffolding – with 5% on VAT

Remove the scaffolding (so assuming a new build or re-roof) and payback is just over 13.5 years. We can get down to a payback of some 11 ½ years if we cut installation costs dramatically (and this will only work when the job is a small part of a larger job). What I am getting at is that roof top domestic solar will make a lot more sense on new roof installations (new homes, re-roof’s) when the work is done by the roofing contractor who is there laying roof tiles anyway. Specialist installers will find it difficult to operate – or to convince home owners that solar is sensible given higher operating and installation costs.

And whilst DECC and others will argue that the industry recovered before and so can do again – I have two counter arguments. One I still think half of the public think that solar “is not worth it” after the first mega-cut in 2011/2012 (despite returns now being as good as ever!). This time round the other half may well be justified in joining them!

News and Reviews

By | News & Reviews | No Comments

News and product reviews

Cernunnos are passionate about renewable technology and sustainable building design. We take the time to truly understand what are the best products for self- build, serious DIY and property developers and how to ensure that these products work to their maximum.

With a multi- skilled team of builders, designers, engineers and technicians and academics Cernunnos are able to continually adapt to the changing energy market and is now one of the leading companies in the UK.

We regularly test, review and complete write ups on new and upcoming products and technologies.

We monitor what are the best financial investments when it comes to heating and energy systems and how to get more for your money.

We disseminate and share latest government and international policy on renewable energy systems and what that means for our consumers.

We practically consider different types of buildings and design projects and how to make them be the most energy efficient.

Explore our resources and begin learning, and winning.

Listed Building Ground Source Heat Pump

By | News & Reviews | No Comments

Cambridge historic building energized by water

Keith Clarke and his family recently moved to River Farm, Haslingfield: a grade II listed building dating back to the 17th Century which was once owned by the pioneering Chivers family, the jam makers.

Ground Source Heat pump listed building

Old river farm

Ground source heat pump listed building

river farm now


The property covers a large farm house, a lake, various outbuildings and just over 4 acres of land. Mr Clarke wanted to change the 20 year old mains gas boiler which struggled to keep the house up to temperature and was expensive to run. Undertaking a 21st century renovation of the property is nothing unusual, however a key component of the process was the installation of a ground source heat pump (a Kensa 24kW Single Phase Twin Compressor) in his nearby lake which provided all the homes space heating and hot water.

Watch the video case study here

In the initial consultation Cernunnos recommended Kensa Heat Pumps as a preferred supplier of ground source heat pumps, because its models are manufactured in the UK and also because the Kensa 24kW Twin Compact, the largest single phase compressor on the market, was best placed to handle the property’s high heat load.

The challenges of working with a Grade II listed property

Keith was aware of ground source technology and knew it was an environmentally friendly choice eliminating reliance on fossil fuels. He approached experienced Cambridge-based renewables installer Cernunnos to talk about designing a ground source system that would meet the family’s heating and hot water needs.

The main challenge was to ensure that the heating system can work at lower temperatures and that
the energy efficiency of the property was considered and improved on. The less efficient the property, the greater the heat loss, which would result in a bigger and more expensive ground source heat pump and associated running costs to maintain temperature in the home.

Cernunnos undertook a detailed heat loss study at the start of the project which showed that the house had previously installed basic insulation measures to improve its heat loss; however the annex building where the heat pump is housed was poorly insulated. Cernunnos therefore installed extra insulation underneath a suspended timber floor using 100 mm rigid insulation between and 25mm below the rafters, as well as adding loft insulation.

The heat loss study also showed that many of the existing radiators on the second floor were already oversized and simply needed upgrading from single to double panels. Oversizing radiators ensures that they will work at a lower flow temperature, thus reducing the amount of work the heat pump is required to do to ‘uplift’ the renewable heat energy from the ground to the required temperature for the home.

Downstairs Cernunnos installed underfloor heating which provided both an even heat and minimal disruption to the original features of the property.

Peter McKeown, Director at Cernunnos said: “underfloor heating provided an ambient temperature delivered by the heat pump, which together with the new radiators ensure an efficient installation all round. We also recommended that the Clarke’s use state of the art Honeywell Evo-Home heating controls to allow them to control the temperature independently in every single room.”

As a listed building Cernunnos worked together with South Cambridgeshire District Council who were whole heartedly supportive to giving planning permission. Peter joked:” the listed buildings officer was even helping us with the digging!”

<H3>Harnessing heat energy from a natural water source</H3>
The lake on the grounds is fed by a natural spring. Cernunnos measured its flow rate, area and depth, and provided this information to Kensa who recommended that the Clarke’s use the heat energy in the lake for their heating and hot water.
The Cernunnos team sunk five specially created Kensa pond mats consisting of 300m of slinky pipe attached to weighted and corrosion resistant stainless steel frames to the bottom of lake. They connected the closed loop system up to the heat pump housed in an annex building via pipes running under the lawn up to the main house. This method removed the need for large amounts of drilling or digging, thereby reducing the cost and duration of the installation.

Keith commented: “When you see the property now it looks totally untouched you would never believe there are pipes in the garden and a heat pump in the lake!”

Chris Davis, Commercial Director at Kensa Heat Pumps said: “More and more people are realising that they can use water as a heat source for their ground source heat pump as it is an excellent conductor. In this case, the Clarke’s lake has a natural stream flowing into it replenishing the energy supply and creating a highly efficient water source system.

“The property had a high heat load on a single phase power supply, so Kensa’s 24kW Twin was perfectly placed to provide the required levels of heating and hot water. The measures that Cernunnos took to improve the heat loss of the building, taking into account its Grade II listed status, meant that the Clarke’s benefit from lower running costs too.”

Saving money through system efficiencies and Government grants

Mr Clarke said: “I knew that ground source was a great technology for extracting the natural heat that’s available from the environment to provide a completely green heating system. The good thing about the pipes being in the lake is that water has great conductivity meaning we are able to extract heat sustainably throughout the winter to keep the house perfectly warm.

“I know that there’s a big investment involved in getting a ground source heat pump, however we realised that we could get the whole thing paid for with the Renewable Heat Incentive, including the installation. Plus, we’ve ended up with a system where the yearly cost of electricity is less than we would have been paying for gas.”

Written by Leemya McKeown

Water Source Heatpump Case Study Cambridgeshire

By | News & Reviews | No Comments

Mr Clarke replaced his gas boiler with a Kensa 24kW Single Phase Twin Compressor to harness renewable heat energy from a nearby lake to provide space heating and domestic hot water (DHW) to his Grade 2 listed farmhouse.

Key facts:

  • 24kW Single Phase Twin Compressor
  • Replaced mains gas boiler
  • Underfloor heating
  • Highly efficient water source system
  • Pond mats sunk into lake
  • Radiator Changes
  • Integrated heating control systems
  • Costs covered by Renewable Heat Incentive (RHI)

    See more

Ground source heat pump trench

Ground Source Heat Pump, Barton Cambridgeshire

By | Installation by Cernunnos Homes, News & Reviews | No Comments

Ground Source Heat Pump and Underfloor Heating Installation


Our client had returned to cambridgeshire buying his ‘forever’ home for him and his family. The property a seventies detached house sits on a large plot of land some 2,790 sq foot. Having to undertake a complete renovation and remodelling of the house, our client wanted to take the opportunity of minimising the costs and find an alternative oil system.

What we’ve done so far

Working with our client we decided to go for the Stibel eltron highly efficient 20 KW ground source heat pump.

Stage 1

Dig a dig dig…. trench digging for ready for putting in the coil

Ground source heat pump trench

Ground source heat pump trench

groundsource heat pump digger

groundsource heat pump digger

Coils system for the tench

Coils system for the tench


Log Gasification boiler Bishop strotford

Biomass log gasification boiler Bishops Stortford

By | Installation by Cernunnos Homes, News & Reviews | No Comments

Biomass System: Angus Orligno 200 25kW Log Gasification Boiler Bishops Stortford


Our client is a tree surgeon by trade and had the intuitive idea of wanting a heating system that he could use the excess wood that he accumulates in his day job. Discussing options with our client wanted to replace the old oil system. The EPC estimated that the annual heating costs would be in excess of £25000 a year!

Log Gasification boiler Bishop strotford

Log Gasification boiler

The Solution

Cernunnos installed An EcoAngus Orlignio 25 kW log gasification boiler, with a 2000 litre Akva Thermal Store. This was installed in a barn, with 35 meter district heating pipe, which connected back to the main house where a 300 litre thermal store which was installed. This replaced the existing boiler – the second store was used to create a small local heat store to save a constant long run from the barn to the house.

Log Gasification boiler Bishop strotford

Log Gasification boiler Bishop strotford

The Outcome

A long term purchase, Biomass is eligible for the Government Renewable Heat Incentive. This has allowed our client to receive annual payments for the next 7 years. The payments were in the region of £4400 per year. Our Client made a total saving of up to £6900 per year. The payback on the system would be just over 2 years.
If you would like to understand more about the pricing and potential paybacks for installing Biomass and learn more about any of the systems in this case study give us a call on : 01223 852267 or drop us a line by filling out the contact form below.

Cernunnos winning team

Cambridge Company Cernunnos wins renewable Energy installer of the year!

By | News & Reviews | No Comments

Local Cambridge renewable energy company Cernunnos
have been awarded “renewable Energy installer of the year” and “renewable project of the year” at the Green Deal & Eco Awards 2015

CAMBRIDGE_002 (Medium)

CAMBRIDGE_064The ceremony is aimed to celebrate and recognise the work of people, projects and initiatives in the renewable energy sector.
Cernunnos established in 2011 has become one of the fastest growing renewable companies in the eastern region.


Working with both domestic customers and local businesses to make the switch to a more sustainable source of energy, Cernunnos have also mademore prominent impacts through their work with Cambridge university and St Faiths school in creating imaginative solar and heating initiatives.

Cernunnos winning team

Cernunnos winning team

The specific wining project was for their eco fit out of Top Farm Barn, Cernunnos’s main headquarters- a display area open to the public where residents of Cambridge can explore and touch sustainable materials, and discuss projects. What makes this project award winning is that although grade ii listed dating back to the 17th century it has been completely transformed. As Leemya McKeown development manager explains. : “the space and the heritage of the property was simply breath taking. However it had been empty for some time. We wanted to bring the property back to life using the latest renewable technologies an sustainable interiors and be an example of best practice’.

Business development Manager Leemya Mckeown

Business development Manager Leemya Mckeown


Cernunnos believe that their high level of bespoke service and expertise they provide to their customers have contributed to their award victory. Director Peter Mckeown said: “It is a fantastic endorsement of what we have done and a great accolade for everyone in the company”.

CAMBRIDGE_082 (Medium)Awards Cermonny

Written by Leemya McKeown

Leemya McKeown

Cernunnos talking about Cambridge local business renewable energy on BBC radio

By | News & Reviews | No Comments

How it all began:- Cambridge, renewable technolgies and South Cambs business support

Cernunnos business Development Manager Leemya McKeown was asked on the Dotty Mcleod breakfast radio show to discuss one of the secrets behind Cernunnos’s sucess.
From a small start up in Cambridge to one of Cambridge’s biggest recent sucess stories, Leemya Mckeown highlights the importance of taking local business support. We also get to find out what she did before she formed Cernunnos. Check the interview here

Leemya McKeown

Leemya McKeown

DSC04905 (Medium)

Written by Leemya McKeown

Freedom at Last – fancy being able to choose the fuel you want to use?

By | News & Reviews | No Comments

Most renewable systems have tended to be focused on fully replacing fossil fuels. Biomass for older homes – and heat pumps for new builds. Houses on oil being the ones that we tend to focus on – as heating with oil used to be so much more expensive that heating with gas (at one stage it was over double the price – today you can actually get heating oil at a lower price than those on mains gas!) 

But the old norm (oil and remove it) is not really true today. Constantly rising mains gas prices (and instability in the UK’s supplies) combined with the generous domestic Renewable Heat Incentive you can look to have a renewable heating system

Domestic RHI – The Right Solution for Each Property

By | News & Reviews | No Comments

Since the launch of the domestic RHI it has been curious to note what a good job the government has done in the schemes configuration. Despite the odd quirk (and the short term disincentive to install solid wall insulation in particular) the scheme we do find does tend to point the homeowner towards the right system for their property.

New builds tend towards heat pumps. If one has land (or deep pockets) then ground source is the best long term solution. Ground source heating is the most efficient of all of the renewable heating technologies – the land acts like a giant storage heater – and as such where it is feasible it tends to be the best rewarded choice for new build properties.

But when retro-fitting, particularly to older homes, a like for like “combustion boiler” solution (biomass) tends to be the most cost effective. Heat pumps work at lower temperatures so we need in general to upgrade most (or all) of the radiators in the home to accommodate such a change. Air source – in larger homes where the heat loss exceeds 15 kW or so – just do not work. Ground source can support larger heat loads in colder temperatures but tend to be prohibitively expensive – unless large amounts of land are available for ground arrays. Below are two examples (real life) that we looked at for potential customers recently.

The first property is a large, well insulated new build home of some 6500 square feet. The estimated annual heating requirement was predicted to be We looked at 4 possible scenarios – Ground Source Heat Pump – the property could only accommodate bore holes – but we did also price it as if it could accommodate a ground array, an air source heat pump, a biomass boiler and a gas boiler. The pricing for the bore holes may be a bit high (as it is a per meter estimate) and all systems included the basic components of a heating system, a hot water tank and a buffer vessel (as it was to have a number of individual heating zones). The biomass included a high quality German/Austrian boiler and a large pellet store – enough to store a years worth of fuel via one single delivery. For the mains gas system we assumed a one off £6000 connection price to have the new mains gas connection installed.

As you can see from the table below that even though the ground source (bore hole) system would be the most expensive solution, it was the cheapest to run over a 15 year period. The RHI and the reduced running costs (ground source heat pump running costs were predicted to be half that of pellets or mains gas) meant that the extra investment up front combined was worthwhile.

Example 1 – Large New Build.
EPC kWh/Annum 35,000
Installation Cost RHI Payments over 7 Years Running Costs over 15 Years Total Cost of Ownership
20 kW GSHP- Ground Array £23,326 £35,348 £17,563 £5,541
20 kW GSHP – Boreholes £35,326 £35,348 £17,563 £17,541
25 kW ASHP £10,598 £12,917 £20,487 £18,169
32 kW Biomass £22,251 £29,890 £39,229 £31,590
32 kW Mains Gas £11,736 £34,642 £46,378

The second property we looked at was an older house, constructed in the 1920’s but extensively extended and renovated in 2006 bringing much of the fabric and windows up to current standards.

The EPC gave a predicted annual heat load of 53,364 kWh per annum. However radiators are sized for “combustion” boilers – not a heat pump. So the heat pump quotes include a substantial sum to install new fan coil radiators that are compatible with heat pumps (or underfloor heating) but with a large number of rooms in the home a substantial £14,000 was allowed for updating 20 radiators (and improving some areas of the fabric to keep the heat load to less than 20 kW – which is the maximum which a single phase domestic ground source heat pump can be designed to accommodate.

For the property in question an air source heat pump could not be installed – with the large heat load we could no find a single heat pump that could meet the demand when the air temperature falls below zero. An upgrade to the electricity supply to a three phase system (the customer was quoted over £15,000 for this) would have been necessary to provide enough electricity to run a dual heat pump solution. 

The customer had no mains gas – so retaining the existing oil boiler as a possible zero capital cost solution could of course be one option. But from the table below you can see that even doing that lead to the highest cost over 15 years of all the solutions proposed.

The table below shows that either a biomass or ground source (ground array) solution would be the best choices. Again the land available would not support a ground array – so again a bore hole system was the only real option. When the additional costs of the bore holes were taken into account it really made sense to look to a biomass system, and again a top of the range boiler with large automated pellet feed was proposed. We did not propose changing the domestic hot water tank but had included a buffer vessel and update to the central heating controls – and had also allowed for an underground pipe to be installed (as the proposed biomass boiler was to be installed in a detached garage) ..

Example 2 – Retrofit to Replace Existing Oil Boiler
EPC kWh/Annum 53,364
Installation Cost RHI Payments over 7 Years Running Costs over 15 Years Total Cost of Ownership
25 kW GSHP- Ground Array £47,142 £35,348 £18,249 £30,042
25 kW GSHP – Boreholes £59,142 £35,348 £18,249 £42,042
25 kW ASHP N/A N/A N/A N/A
30 kW Biomass £22,476 £29,890 £36,738 £29,325
30 kW Oil £52,780 £52,780