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It was installed in 2017. No, nothing we could do because they used the word estimate. Here is the reply I received when I queried the difference
The MCS heat loss calculations we use to design the heat pump system take into account only the heat loss through the fabric of the building – no account of the heat gains from sunlight, metabolic gains (i.e. body heat) or from the appliances / lighting in the building is included, so the heat loss is relatively high. This means that the heat pump system is capable of maintaining the desired temperature in the house at the design climate, regardless of the potential prevailing conditions internally.
RHI payments are based on the energy requirement of the building as defined by an EPC, which does take additional gains into account so the result is almost always lower. In most cases the EPC figure is in the region of 25% lower, but this does vary from building to building.
Variation can be related to the type of dwelling – new build properties have to meet certain criteria to pass building regulations so variance tends to be lower than in renovation/retrofit properties, but this isn’t always the case and it may not be obvious why. Because the two assessments use different mathematical models there is always potential for an amount of disparity between the two which is not always predictable.
We have also seen considerable variation between EPCs produced for the same dwelling by different assessors. The EPC is produced using software called rdSAP, which requires the assessor to choose element types from a series of menus; there are a number of wall types, floor types etc from which the model is populated. Different choices made by assessors can have a considerable effect on the result.
On your quotation and the graph that was supplied it is noted that the calculation is an estimate, that annual payments include a presumed RPI of 2% and that the heat loss calculations used may differ to the values calculated in your EPC. We try to offer an objective and realistic estimate of the potential RHI payment your heat pump system may generate, but due to the potential variation in the models it can only be an estimate.
It's extremely naughty that they base their figures on the MCS heat demand figures and RHI is actually paid out on the EPC figure.
Can't fault our installers in any other way though. they were extremely professional throughout and have had no issues with the heating. Our property was a new build btw. |
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26-11-2019 03:44:26
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