Energy Performance Certificate

[Mike44]

Hi Guys
Just a quick question for you
A couple of weeks ago I had British gas come and fit me a new boiler a (Worcester 532i)
The week after I had someone come to do me a "Energy performance certificate"
The lady who did the energy check couldnt find my new boilers model number, and said she would Google it latter
Any way my energy performance certificate arrived to day and my boiler has only got 4 out of five stars
But when I check on the Worcester website my boiler is a "A rated" boiler
Has the lady got it wrong ? maybe googled the wrong boiler model number
How can a A rated two week old boiler not get full marks
Sorry if I got this wrong guys, but has she got it wrong ?
Thanks for any advice
Regards
Mike

 

[Tibbot]

I imagine no fossil fuel burning appliance achieves top marks and that 5 star ratings are reserved for renewables.

 

[D_Hailsham]

The A to G ratings have now been dropped, although manufacturers still show them. This is because the method of calculating the rating has changed to make it more realistic. The BG 532/I was 90.2% efficient, using the SAP2005 method for measuring efficiency. As it was over 90% efficient, it was given an A grade. Under the current, SAP2009, method it is only 89.4% efficient.

Either the lady who did the assessment doesn't understand the change in rating method or BG are trying it on by applying the old (2005) A to G rating scale to the new (2009) calculated percentages.

 

[iwaters]

The SAP methodogy is the calculation method used for the EPC. The efficencies of the boiler is the SEDBUK efficency which is used by the SAP methodology. In SAP2005 there was one efficency for boilers, in SAP2009 there is a summer and winter efficency number. The DEA couldn't not be using SAP2005 methodology as she wouldn't be able to lodge the report on the central register. In fact the DEA uses RdSAP as the full SAP calc is only for new build properties.

However this isn't the issue here. The banding is worked out by dividing the unit cost of the fuel by the efficency of the appliance. The cost of gas comes from a standard table. The price per kWh being 3.10p In order to get 5 strts the ratio needs to be less than 3.4. So if you have a boiler which is 90% efficent the ratio is 3.44 which is 4 stars. For a gas boiler it needs to be at least 91.5% efficient to get 5 stars. Your boiler is liekly to be around the 90% mark so you are very close to 5 stars.

Something like an ASHP would get 5 because of the very high efficencies.

I write RdSAP software for EPC production for a living.

 

[D_Hailsham]

However this isn't the issue here. The banding is worked out by dividing the unit cost of the fuel by the efficiency of the appliance. The cost of gas comes from a standard table. The price per kWh being 3.10p In order to get 5 stars the ratio needs to be less than 3.4. So if you have a boiler which is 90% efficient the ratio is 3.44 which is 4 stars. For a gas boiler it needs to be at least 91.5% efficient to get 5 stars. Your boiler is likely to be around the 90% mark so you are very close to 5 stars.

When was the 'star' system introduced? There's no mention of it in SAP2009?

According to the Sedbuk database, the most efficient boiler is only 90.3% efficient (SAP2009) so no current gas boiler is graded five stars.

 

[iwaters]

It was introduced when SAP changed to 2009. RdSAP version 9.90. Previously it was a graded system (Good, Very good etc.).

The banding spec document is separate from the SAP2009 spec as SAP was previously used outside of EPCs and the information has always been kept separate.

It's no coincidence that a gas boiler can't get 5 stars.

 

[D_Hailsham]

I see. The 'star' rating system is only used with EPCs. An 'A' rated boiler will never get more than '****'.

So what can achieve the ultimate prize - '*****' ?

 

[iwaters]

Heat Pumps will get 5 stars. Although electricity is more expensive than gas they can have efficencies of over 300% which means the get the 5 stars.