Improving Energy Performance Certificate ratings through use of better technologyHeat pumps for hot water provision

Producing hot water by direct electric fuel type is inefficient overall. The main direct electric system for hot water involves a cylinder with direct electric immersion heater. Alternative types include instantaneous hot water provision. Instantaneous hot water provision is often found where the demand for hot water is limited and instances include staff toilets in a retail environment, small office or small industrial area. Immersion heaters as they are often referred to are widespread and where the demand for hot water is high such as a restaurant, takeaway, café or pub the energy associated with their use is often high.

Solutions to direct hot water vary dependent on fuel source available. As an alternative to gas and direct electric is to use a system utilising heat pump technology. Heat pumps are covered in another article however the most common and easiest type of heat pump is an air to air heat pump.

When carrying out surveys for Energy Performance Certificates, the most common type of air source heat pump encountered is a Stiebel Eltron 300. At time of writing these packaged air source heat pump cylinders have a coefficient of performance, efficiency of 3.4 (340%). Direct electric hot water heaters have an efficiency generally termed as 1.0 (100%). These hot water heaters generally provide 3.4 times the efficiency of hot water provision.

When calculating the Energy Performance Certificate rating hot water demand is defined for all occupied spaces in kWh/m2 and expressed in kgCO2/m2 based on fuel type. For example the demand for an office is assumed to come from the occupants washing hands and making tea. Heat losses from storage and distribution are added where appropriate. The EPC software assumes hot water demand for an office at This demand is relatively low In restaurant environments where hot water demand may In the UK 1 kWh of electricity generates 0.34885 kg CO2 emissions. (2017 UK Government conversion factors)