Most energy assessors will know NHER purely as the accreditation scheme that quality assures their EPCs. Some might not know that it also refers to a rating scale for assessing the energy efficiency of new and existing homes. Below, I’ll explain the key differences between the NHER and SAP scales.
Development of the NHER rating
First, a bit of history. The National Home Energy Rating scale was launched in 1990, based on the results and feedback from the Milton Keynes Energy World project. NES (then Energy Advisory Services Ltd) took the Milton Keynes Energy Cost Index and extended it to provide national coverage. This in turn gave rise to the introduction of SAP in 1995.
NHER ratings versus SAP ratings
Clearly there are different space heating requirements in the different parts of the UK, but SAP (Standard Assessment Procedure) assumes that each dwelling is located in the East Pennines. NHER ratings take into account both the region of the UK and the immediate environment of the dwelling.
NHER ratings include an estimate of fuel use for cooking and appliances, which are not part of SAP. This gives a fuller picture of energy usage and running costs in the home. For an NHER calculation you can also enter the actual number of occupants in the dwelling, and the actual way the dwelling is heated. SAP uses Standard Occupancy, and a Standard Heating pattern. The NHER rating gives a more accurate estimate than SAP of the energy used, CO2 emissions and running costs. We have found that the running costs are beneficial to Social Landlords in setting and monitoring Affordable Warmth/Fuel Poverty Strategies.
On the SAP scale, dwellings are given a rating from 1-100+. A SAP rating of 92 or greater puts the dwelling in the A band. On the NHER scale of 0 to 20, dwellings are not put into bands. An average dwelling in England would score between 4.5 and 5.5 on the NHER scale, whereas a gas-heated masonry semi meeting Building Regulations Part L1a 2006 would score approx NHER 10. A dwelling with an NHER rating of 20 achieves zero CO2 emissions along with zero net running costs. Here, you would expect to see very high energy efficiency, efficient low carbon heating, and renewable generation.
NHER ratings in our software
We build NHER ratings into our desktop software used by our members: Plan Assessor v4.5 contains NHER outputs for new build dwellings, and Stock Assessor v2.1 gives NHER outputs for existing build dwellings.