Why is my EPC rating so poor with my new biomass boiler?
Posted by Tasha Kosviner on 12 September 2013 at 9:58 am
Q: Following the installation of a super-efficient biomass boiler, my energy bills dropped but my energy performance certificate (EPC) rating plummeted 26 points to a G. I’m convinced that the report is incorrect but where do I turn to get this corrected?
We removed a 20-year-old boiler which, at peak efficiency cost around 6.8p/kWh to run. We replaced it with a 92 per cent efficient biomass boiler. As a result we have seen a massive drop in heating bills without any changes to the fabric of the house. Imagine our shock then, when this reduced our EPC rating by 26 points to a G. Upon further digging, we discovered that the explanation for this is that when it comes to assessing biomass pellet stoves for the EPC, they are given a generic efficiency rating of 65 per cent.
A: Your EPC is prepared using a ‘SAP rating’ standing for standard assessment procedure. This is the government’s recommended system for assessing the energy efficiency of your home. The SAP charts are divided into seven bands ranging from A to G with each band having a set amount of SAP points. If your home scores 1-20 points, it is rated as G, 21-38 points qualifies you for an F rating and so on, with 92-100 points netting you the highest rating, A. You would rightly expect that by replacing an out-of-date, expensive and inefficient boiler with a brand new, energy efficient biomass boiler, your rating should go up, not down.
However, two things are at play here that are contributing to the drop in your energy efficiency rating. Firstly, you should be aware that the EPC rating is based on the cost of heating a home, so that while taking into account the efficiency of the boiler itself, it also makes adjustments according to the price of the fuel used in the boiler.
Wood pellets are more expensive per kWh of heat delivered than some other fuels, like mains gas and heating oil, so when this is taken into account the overall rating is lowered. Of course when looking at the environmental rating, the wood pellet boiler would achieve a higher score than either of those two fuels, but it's the cost-based score that appears on the front of the EPC and on which the rating band is based.
Secondly, and more worrying, is the way in which the energy efficiency of your boiler is being calculated under SAP. The 65 per cent rating that you refer to in your question is the generic figure that SAP software assigns to biomass boilers. The software can only accept a higher efficiency figure for your biomass boiler if that specific make and model has been added to the SAP product characteristics database.
To go into the database, the manufacturer has to provide evidence that the efficiency they claim is supported by formal test results. It has to have been tested by an appropriately qualified test lab, as required under the construction products directive. For boilers that are included, the software is able to use the manufacturer's declared efficiency, rather than that default you mention, but otherwise the default must be used.
As our energy expert Linn Rafferty points out, the solution is clear: “Your boiler needs to be in the database,” she says. “However, this can’t happen unless your manufacturer applies for it to be included. Therefore the organisation you should turn to is the manufacturer to suggest that they apply for inclusion in the SAP product characteristic database.”
Manufacturers who wish to submit data about their products for inclusion in the database should contact Kiwa GASTEC at CRE, The Orchard Business Centre, Stoke Orchard, Cheltenham, Gloucester, GL52 7RZ (phone 01242 677877).
If you are considering installing a biomass boiler with a view to upping your EPC ratings, you should check whether the boiler’s listed on the database first. There are currently only 13 woodchip and wood pellet boilers listed although HETAS, the trade body representing biomass and solid fuel heating domestic heating appliances are encouraging manufacturers to get listed.
More information about biomass boilers from YouGen
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