The Renewable Heat Incentive will use the process of “Deeming” to calculate the tariff payments made to a household or business. But what exactly is “Deeming”, and how will it affect the return on investment?
What is Deeming?
Firstly, “Deeming” is the process whereby a building will be assessed on how much heat it actually needs to heat it to a certain temperature. Thus, the payment from the RHI will be based upon the amount of heat required to heat a property, rather than the actual amount of heat used by that property over a certain period.
Why Deeming?
Deeming overcomes several problems, including:
- Measuring the amount of renewable heat generated by a system is difficult and technologically expensive
- the property will be measured on what it needs rather than what it produces, thereby overcoming the problem of excess heat generation or heat dumping (whereby a property is over heated to generate more income and this heat is then dumped by opening a window).
- It encourages basic energy saving measures such as better insulation so that less heat is required for the property.
- It rewards more energy efficient houses over less efficient ones.
How is it done?
The Domestic Hot Water and Space Heating requirements for any building will be estimated using the BREDEM (the Building Research Establishment Domestic Energy Model). This is a standardised model for estimating the amount of energy required by a property for space heating and Domestic Hot Water (DHW). It is a simple, long established, method of estimating energy use. It considers both the physical aspects of a property AND the lifestyle of the occupants. That said, it does not take into account how the occupier actually uses the heating system, but takes a standard level of heating requirement (21 degrees for a living room, and 18 degrees for other areas, with 2 hours of heating used in the mornings and 7 hours at night for weekdays, with 13 hours a day at weekends). This way, it produces a very standardised energy rating for a property, disregarding the individual occupiers preferences for how hot/cool they actually use the property, thus allowing homes to be compared on a like for like basis. For Hot Water requirements it ignores the actual number of people that actually live in a building, but focuses on the actually floor area of a building, assuming that a larger floor area will have more people living there. In essence, it will provide an energy rating that is independent of the size of the home, providing an energy rating per square meter. The model gives accurate results, often within a +/- 10% reading of actual data readings.
What are the effects?
- More energy efficient homes will benefit. If you have 2 properties of the same size, the one that actually uses less energy to heat the home to the BREDEM standards will benefit from the RHI payments more than the less energy efficient home.
- Larger houses with lower numbers of occupants will benefit as BREDEM will assume there are more people living there than there actually are. Thus the BREDEM rating will overstate the amount of domestic hot water required.
- Those that heat their homes less (i.e. people who do not use their home all year round) will benefit from a higher BREDEM rating and subsequent RHI payment.
