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A point of view: The problem with EPCs

Posted by Tim Tucker on 17 October 2018 at 10:13 am

If you want to update an out of date or expired Energy Performance Certificate (EPC), you may be in for a nasty surprise. You may get a worse one, even if you have added numerous improvements to your house.

Five years ago, our children told us to downsize. So we did. We bought a 5 year old south-facing house, to which we added a 4 kWh solar PV array. We also added an Energy Recovery gadget (also known as a power diverter or Solar PV optimiser) which heats our hot water from the solar PV throughout the year, so we do not buy gas for hot water. Apart from that we added a porch before the front door which reduced heat loss, and an unheated conservatory on the south side which is thermally insulated from the rest of the house. However the conservatory is capable of heating the whole house on a sunny day in winter if we open the French window from the sitting room. In addition, extra roof insulation was added to the roof space, and all the lighting was changed to low energy.

But our energy suppliers would not believe our lower consumption, so we had to call in the ombudsman, who ruled in our favour, and we got over £800 back. We then changed our energy supplier.

But the biggest change came when we installed batteries in February 2017. Since then we have not drawn any electricity from the grid, which meant that our new energy supplier reckoned that our meter was faulty. They changed the meter, and we are still not buying electricity.

The original EPC expired in August 2018, so, as we are both in our late 80s, we applied for a new one to save our children trouble when we leave this world.

The assessor came, and duly awarded us a rating of 75. This was lower than the original rating of 77, but still a C rating. So I complained, and 9 days later I found that my rating had been changed to 90. 90 is a B, and just two points below an A rating.

Looking into the reasons for this sudden change, the only ones I could find were that the porch and the conservatory had been treated as extra space to be heated, instead of extra insulation. The extra roof insulation had not been taken into account either.

Nevertheless the latest EPC still says that my “Estimated energy costs for this home” at £1,887 over 3 years. This is actually just over twice what I am actually paying my energy supplier, where I am £235 in credit. But you get a ready answer to this: The costs of energy are going to go up, and, “the figures are always based on the same assumption – that the property will be heated for 9 hours per day for 5 days per week, and 16 hours per day for 2 days per week.” In other words, for a house inhabited by working families. But my wife and I are retired, and live in the house almost all the time. So this argument does not add up either. The other part of the assumption is that the living room will be heated to 21 degrees and other living spaces to 18 degrees.  If the house is heated to a lower temperature than this assumption will not give an accurate calculation

But the biggest reason for the difference is that the “methodology” used by assessors is that neither the Powerflow batteries, nor the Powerflow Energy Recovery System I have installed are accepted by the “methodology”. Yet putting those two items into my system have given me the greatest energy savings of them all.

So if, or when, the government recognises batteries, we ought to get an A.

Carefully adding to your house’s eco credentials can pay large dividends. Before putting in batteries, I worked out that my Return on Investment (ROI) was just over 15%, which is better than you get anywhere else at the moment. But the ROI after putting in my Powerflow batteries must be even better, because we have now almost completely eliminated our buying of electricity.

EPCs, which are legal documents, do not realise this. You need them when buying, selling or renting houses. You also need an EPC with a D rating or better if you want to claim Feed in Tariff after installing solar PV.

In the latter case, do not do as I did. Do not ask the estate agent who sold you the house for an EPC. Mine charged me 3 times the going rate, and I ended up with an assessor who gave a wrong reading. Instead, ask the firm you have chosen to install your solar PV, or go to the Government’s register of assessors to be found at


Here at YouGen we will ocassionally accept blog contributions from our readers if they are interesting, relevant and abide by our writing guidelines. These articles represent the views of individuals and do not necesserily reflect those of YouGen or NEF. 


About the author:

The author is one of our older contributors. In 1961, after 9 years in the heat of India, Tim bought a plot of land in England and employed an architect to put a house on it. When he asked the architect to consider two inches of fibreglass in the roof space and some double glazing, he was told not to waste his money. ‘It is much cheaper, just to turn the heat up.’  After that experience he has been obsessed by energy conservation.

Working since in winter in places such as Kazakhstan, Estonia , Finland and Romania has not changed Tim's desire to come home to warmth, and to lower heating bills.

If you have a question about anything in the above blog, please ask it in the comments section below.

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10 comments - read them below or add one


followersaustraliaComment left on: 22 December 2020 at 6:59 pm

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followersaustraliaComment left on: 22 December 2020 at 6:59 pm

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NorthGlosEPCComment left on: 26 March 2019 at 6:27 pm

Well I am an EPC assessor and i must say reading all these comments It's both encouraging and discourageing. It's good that people take the ratings and the effect of various upgrade measures seriously but discouraging because I feel there is something of an unrealistic expectation as to what level of accuracy and detail the EPC survey should actually provide. 

It's called RdSap, reduced (very much) SAP, The methodology is fairly simple and limited in range to the more common efficiency measures one might expect in the average UK home. 

Most people commenting are commendably well into energy efficient living and happy to explore the most exotic of measures to achieve better efficiency. For the the EPC the RdSap methodology is a very blunt instrument indeed and unexpected, even seemingly illogical, ratings often result because the exotic measures involved are simply not covered.

We should remember just what the purpose of the EPC is. 

It is a very approximate guide for potential buyers and tenants. It tells them without even seeing the property whether there is a modern heating system, how well it's controlled, an indication of general levels of insulation and where obvious improvement can be made. And that is really about it.

Most surveys take no more than 45 minutes on site and perhaps another hour to complete the job. Then there is travelling time to and from. One commenter above boasts he got his completed for £35. Now bearing in mind that includes all the assessors cost plus lodgement with the data base what exactly did he expect for £35? Days of research to track down all the aspect of that properties particular setup? Afraid not. No one gets rich providing EPC's and as a full time job it's very inlikely one could even afford a mortgage. For most assessors it's unlikely to be their only income source, rather it is supplimenting something else, or something else suppliments it.

The reason I go on about accuracy and cost is that the EPC is fine for what it is intended for and gives a good general indication of the energy efficiency of the vast majority of properties. However for cutting edge high efficiency properties occupied by people very keen on getting these high efficiency achievements recorded it's not really the thing to use, nor was it intended to be, so criticism of the limitations of the methodology is rather inappropriate especially when you consider how little an EPC actually costs you.


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cannonballdazeComment left on: 13 February 2019 at 7:56 am

Hi, I'm sure that I've read that if you have significantly low consumption, you become ineligible for FIT payments ?

Can anyone shed some light on this.

Cheers - Joe

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JCapiroteComment left on: 14 November 2018 at 9:10 am

It is also interesting to note that when I installed my 4kw solar PV panels I had some work to do to get the house down to band D from E. In my specific case I had NO heating in the house at all as the gas boiler had expired, it was already a reconditioned warm air boiler when it was installed in the 1960s and I refused to replace it with an overpriced gas fed boiler system. 

Anyway, because I had no heating I was penalised and actually managed to improve the rating dramatically by ‘installing’ some £20 infra-red heaters from a local hardware store. 1 in each bedroom and 1 in the lounge did the trick along with an extra 4 inches of insulation in my loft taking the total depth to 10”.

It was deemed more energy efficient to have ‘installed’ the heaters than not, crazy!

I did not see the point in spending £2-3,000 on a condenser boiler heating system I had no intention of using to get a few pounds back in the increased production payment from the FIT

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SlotsComment left on: 31 October 2018 at 4:03 pm

I'm 70 and I agree about EPC and how they are produced. We are about to downsize and move so I got an online company that deals with freelance assessors to to provide our first ever EPC. The cost was £35 for the EPC and £20 for the floor plan. The property is now on sale online and we avoided the estate agents hefty mark up.

We got a C 75 rating at 159 kWh/m2 just short of a B. When I challenged the assessor by saying our Primary Energy per Square Metre of Floor Area (kWh/m2) was working out at 112 kWh/m2 he said it was the assumptions in the rating process that were causing the difference.

I have kept a record of Gas and Lec on a spreadsheet since 1983 The graph of kWh/m2 shows a straight line decrease which hit the EPC 159 mark back in 2002. The way we acheived further falls was by replacing engergy hungry appliances by more efficient ones. All our refrigeration has A+++ ratings.

Last year 2017 we replaced a state of the art Dutch solo gas condensing boiler installed in 1999 with the same make only this time it was a combi boiler with an IoT thermostat. This boiler has an inbuilt cold water preheater from flue gasses that makes hot water heat recovery about 6% better than it might otherwise be.

I have a small scale solar install of about 800W that dumps excess energy through a solar hot water device into an oil filled radiator meaning nothing goes back to the grid. I can manually switch the number of panels in use. At the new house I will invest in batteries and larger PV which should lower the Lec consumption. Gas heating though is the largest part of of the present 112 kWh/m2 being consumed.

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ToffComment left on: 31 October 2018 at 3:29 pm

Add zoning (Honeywell Evohome) then,  for EPC purposes, energy savings will largely be ignored as the Database treats Evohome as just two zones with 3 TRVs. The bottom line is that if it hasn’t been tested by BRE then the EPC software will treat the system as unspecificied (generic). I was 1 point away from an ‘A’ EPC. Evohome might just as well have been left in its box. Fortunately, my buyer was fascinated by it.

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Ben Whittle

Ben WhittleComment left on: 31 October 2018 at 1:33 pm


Whilst infrared panels are certainly "efficient" in that they turn nearly all the electricity they use into heat - that doesn't mean they are green. It's still more envirnmentally friendly to use gas, oil or heat pumps than direct electric heating.

The benefit of infrared heating is that you only use it when you want it (assuming its manually turned on not timed) and onlys use it in the rooms where it is turned on. If you did the same thing with central heating it would be greener

Thermal mass does not equal insulation - it just slows down heat transfer


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snozwangleComment left on: 31 October 2018 at 12:08 pm

Tim's various experiences are all too common, especially electricity retailers not believing energy savings after fabric improvement and renewables installation.

Naturally, they rely on computer algorithms to try and trip us up (charge us too much), but the algorithms are far too simplistic to be realistic when bespoke improvements are made to the energy performance of a dwelling.

This failure to reflect reality not only applies to consumption, it applies to FIT payments for solar PV generation too. I have been told several times by my FIT scheme administrator that my regular generation reports are too high. I wouldn't be surprised to find that the algorithm they are using to produce a benchmark is based on insolation levels in Scotland - Kent is somewhat sunnier!

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LizanneComment left on: 31 October 2018 at 12:05 pm

I had a similar experience with my 200-year-old mid-terraced cottage in Cornwall, whereby the algorithm to produce an EPC couldn't take into account that the 2ft-thick external and internal walls contributed thermal mass and my wall "mirrors" in all rooms were in fact Infra-Red heating panels providing extremely efficient and cost-effective room heating (especially as we had a Solar PV installation on the rear roof) so that the (pre-existing) gas fires in the lounge and dining room were just for "effect". 

I was "marked down" for not having a condensing boiler - even though I had no central heating???? - the on-demand multipoint water heater was all that was needed to supply kitchen and bathroom taps.

We went to a great deal of trouble to future-proof our home for our retirement and now find it is misunderstood and unappreciated by prospective buyers :(

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