The main and secondary space heating systems are identified based on DEAP Appendix A. In some cases, it may be necessary to make a cost-comparison between two or more heating systems to see which is the cheapest to run, as outlined in DEAP Manual Appendix A, Section A2.
This is done by calculating the BER for each main heating system in turn and noting the Delivered Energy in the DEAP Results tab. The Delivered Energy (in kWh) is multiplied by the fuel cost (in €/kWh) to give the annual cost of running the dwelling for each of the heating systems. The fuel cost data can be taken from the SEAI Domestic Fuel Cost Comparison file here.
A dwelling with three habitable rooms and two heat sources present: an open fire and a direct-acting electric heater. Each heater heats only one habitable room. Therefore, the cheapest to run is chosen as the main space heater.
The BER was first calculated with the open fire (efficiency = 30%) as the main heating system and the electric heater (efficiency = 100%) as secondary. Fuel costs in the example below are based on prices published in October 2011.
The BER was then calculated with the electric heater as the main heating system and the open fire as secondary:
When changing the main heating system above, it will typically also be necessary to make changes on the ‘Space Heating > Controls And Responsiveness’ tab to reflect a different level of control and responsiveness in the main heating system.
Each value is multiplied by the respective ‘Unit Fuel Cost’, taken from the ‘Domestic Fuel Cost Comparison’ file, to give the annual running cost.
In this case as the second option is cheaper to run, the electric heater is chosen as the main heating system and the open fire as the secondary system.