* Based on comparing the savings for upgrading a G-rated to an A-rated condensing boiler with a full set of heating controls. Savings assume a gas price of 4.21p/kWh. Source: energysavingtrust.org.uk/Heating-and-hot-water/Replacing-your-boiler (03/15). Boiler Efficiency Guide tool provides a guide on potential energy savings based on your property type and model of boiler (see SEDBUK/SAP 2005) it does not take into account season variations in the climate which can affect the gas consumption. Older appliances that have not been assessed under the SEDBUK methodology have an 'estimated efficiency' and their efficiency has been determined using Table 4b of the Government’s Standard Assessment Procedure for Energy Rating of Dwellings. (EE = Estimated Efficiency).