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Seasonal performance factors and RHI: should I get a reassessment?

You’ve had a heat pump installed (prior to the launch of the RHI), you’ve had your green deal assessment, you’ve got your MCS certificate and you’re poised to apply for the government’s newly-launched renewable heat incentive (RHI) scheme.

But hold on – what’s this?

A question in the application about whether you want to use your deemed SPF of 2.5 or another figure. What does that even mean? You thought this was supposed to be simple, right?

Well yes, it was, but then Ofgem realized that paying incentives based on the type of renewable heat installation you have, wasn’t simple either. In order to make the incentives work properly, they needed to look at not just the type of technology you have installed, but also at the efficiency of that installation.

The efficiency of a heat pump installation depends on the temperature the water in the pipes needs to be maintained at, in order to have a warm home. And this depends hugely on both the efficiency of the heat emitters you use – for example, radiators or underfloor heating – and on the heat demand of a room. To put it bluntly, if you connect an air source heat pump to traditionally small radiators in a room with three outside walls and as many windows, it’s going to require a whole lot of heat to keep it warm. If you connect it up to an underfloor heating system in a room with a single, triple-glazed, south-facing window, then you’ll need much less energy to heat it.

Thus the SPF or seasonal performance factor was born.

The SPF assigns an efficiency rating to your heat pump based on the required temperature of the water flowing through it. The lower the flow temperature, the more efficient your system and the higher your SPF.Crucially, the higher your SPF, the higher your RHI payments will be.

In new systems, that is in systems installed after the launch of RHI on 9 April 2014, the SPF is assessed using the MCS’s heat emitter guide and the figure you find on your MCS certificate will be the one you can use in your RHI application.

But for legacy systems, that is systems installed before the 9 April launch, your SPF will probably have been ‘deemed’, or fixed, at the relatively low 2.5. This is because prior to the launch, there was not an industry standard for calculating SPF so Ofgem has no way of checking your installer’s SPF calculations for accuracy.

In order to get a more accurate – and potentially higher – assessment of your system, you will need to get a reassessment of your home.

The reassessment will involve your installer coming out to do a room by room assessment of your property. Each room will be assigned a heat loss calculation and then the installer will look at the means you have employed to emit heat into that room – for example, outsized radiators, traditional radiators or underfloor heating. Those figures will then be used to arrive at the SPF calculation.

The calculation you are given will be based upon the heat demand and heat loss calculations of the least efficient room in your house so be warned – your home can be let down by the use of just one inefficient radiator, in a sea of otherwise underfloor-heated rooms.

As a very broad guide, if your heat pump is linked up to underfloor heating in a highly insulated house, it is possible that your SPF will be considerably higher than 2.5; if it’s linked to traditional radiators, and you have minimal insulation over the minimum requirement, it’s likely that 2.5 won’t be far off. Ground source heat pumps are likely to achieve higher ratings than air source heat pumps.

Robert Meeks, a commercial sales manager for ICE Energy which has installed over 11,000 heat pumps, has come up with these figures to give an idea of what a higher SPF rating might mean for a typical 3-bedroom property.

A typical 3-bedroom property has an annual heat consumption of 20,000kWh. At an SPF of 2.5 the renewable energy component of this is 12,000kWh. But with an SPF of 3.4, the renewable energy component is 14,120kWh. In this case, upgrading the SPF to 3.4 would yield an additional 2,120kWh of additional renewable energy. If you have a ground source heat pump it would result in an increase to your RHI payments of £398.56 per year at a rate of 18.8p/kWh, or £2789.92 over the seven years of the scheme. For an air source heat pump, this would result in an increase of £154.74 a year, or £1083.32 over seven years.

Remember though that there are lots of variables and the only way to know for sure what your SPF is is to get the assessment done.

Whether you choose to get an assessment or not will probably depend on you balancing the likely increase in SPF – and consequently your RHI payments – against the cost of getting the assessment done. I’ve heard of one company that is charging £240 for the assessment. However, apart from that upfront cost, there is minimal risk involved: if you do get an assessment done and it comes out at below 2.5, Ofgem tells me you can always ignore it and opt for the deemed SPF of 2.5 in your application.

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