Heating summary

For any heating system the performance obtained (in terms of running costs) will depend upon a number of parameters. The main parameters, and how they influence running costs, are tabulated below.

Parameter		Influence on performance
Efficiency of the heating appliance	For appliances that burn fossil fuels the construction of the boiler can have a large influence on how efficiently it burns fuel. For example, in all such boilers there is heat lost to the atmosphere from the flue gases that result from combustion. Condensing boilers extract part of that waste heat and 'recycle' it back into the system. This makes them more efficient than non-condensing boilers.
Age of the heating appliance	Older appliances are likely to be less efficient - if so they will need to burn more fuel for the same heat output.
Capacity of the heating appliance	Appliances are generally more efficient when operating at maximum heat output - smaller appliances are more likely to operating at or near maximum output for more of the time.
Heat loss characteristics of the dwelling	This will be dependant on the size and shape of the structure, and on the levels of insulation present in the external envelope.
Heating controls	The effectiveness of the controls has a significant effect on the operation of the whole system. For example, for a normal 'wet' central heating system a 'basic' set of controls would comprise programmer, room thermostat, cylinder thermostat, boiler interlock, thermostatic radiator valves (TRVs) on all radiators (except those in rooms with a room thermostat) and an automatic bypass valve if required. Well-controlled systems can be more than 30% cheaper to run than poorly controlled systems.
Heating regime set by the occupants	The more the heating system is used, and the higher the temperature settings on thermostats, the more fuel will be burnt.
Climate	Dwellings in colder climates (e.g. northern regions) will have greater heat losses and therefore require more fuel to maintain a given internal temperature.

For fossil fuel boilers the above parameters will affect the overall operating efficiency to different extents. Therefore, in order to allow different boilers to be compared, an index - SEDBUK¹ - has been developed under the Government's Energy Efficiency Best Practice Programme with the co-operation of boiler manufacturers, and provides a basis for fair comparison of the energy performance of different boilers.

SEDBUK is the average annual efficiency achieved in typical domestic conditions, making reasonable assumptions about pattern of usage, climate, control, and other influences. It is calculated from the results of standard laboratory tests together with other important factors such as boiler type, ignition arrangement, internal store size, fuel used, and knowledge of the UK climate and typical domestic usage patterns.

For estimating annual fuel costs SEDBUK is a better guide than laboratory test results alone.

It can be applied to most gas and oil domestic boilers for which data is available from tests conducted to the relevant European standards. The SEDBUK method is used in SAP (Standard Assessment Procedure).

Because of these factors, it is not possible to give a single value for the running cost or carbon emissions. However, in order to gain some understanding of how different heating systems compare, the table below has been prepared. The values in this table have been calculated using the BREDEM 12 (BRE Domestic Energy Model), which is the basis for the SAP energy rating method. A typical heating pattern was used, with the whole house heated to a good standard. Then for both the cash and the carbon emissions, two figures have been calculated, representing the running cost and carbon emissions that would typically result if the house were insulated to different standards as follows:

Lower figure - insulated cavity walls (U=0.466), 250mm loft insulation (U=0.16) and a 75mm hot water tank jacket.
Higher figure - no loft insulation (U=2.3), solid walls (U=2.1), no hot water tank insulation

Fuel costs and carbon emissions for a typical semi detached

		All fuel use 2				Space and water heating only 3
		£/yr running cost		kgC/yr		£/yr running cost		kgC/yr
		From	To	From	To	From	To	From	To
Electric peak heating	950	1780	1595	2915	750	1580	1195	2515
Modern elect storage, automatic control	645	1180	1825	3615	445	980	1425	3215
Bulk LPG central heating (90%) 4	635	1065	1260	2245	435	865	860	1845
Air source heat pump (250%) 4	575	990	1115	1885	375	790	715	1485
Solid fuel boiler system (65%) 4	540	945	1980	3875	340	745	1580	3475
Wood pellet boiler system (65%) 4	495	850	525	675	295	650	125	275
Electric Ground source heat pump (300%) 4	470	745	975	1570	270	545	575	1170
Gas central heating - typical of stock (67%) 4	465	720	1335	2340	265	520	935	1940
Electric Ground source heat pump (320%) 4	455	720	955	1520	255	520	555	1120
Oil central heating - A rated (90%) 4	405	645	1335	2405	205	445	935	2005
Gas central heating - A rated (90%) 4	400	595	1075	1845	200	395	675	1445
Source BRE

Solar water heating
Although solar panels might strictly be regarded as a heating system, they are almost always used as a means of reducing the burden placed on the main heating system. Thus the data given in that section relates to savings on fuel bills and carbon emissions in the same way that data is presented for insulation and other fabric measures. For that reason solar water heating has been included in the section on fabric measures, rather than in this section on heating systems.

Technical guidance available
» GK 31 'BRE Domestic Energy Model', BREDEM SAP 2001

» General guidance for choosing heating systems is found in:
» CE29 'Domestic heating by oil: boiler systems' 
» CE30 'Domestic heating by gas: boiler systems'
» CE47 'Domestic heating by solid fuel: boiler systems'
» GIL59 'Central Heating System Specifications (CHESS)'
» Guide to heat pumps

» Click here for additional Best Practice publications on heating.

¹SEDBUK stands for Seasonal Efficiency Database for Boilers in the UK.

²For the figures headed 'All fuel use' £200 has been added to the figures for space and water heating only to reflect the cost of cooking, lights and appliances. A similar approach is taken for carbon emissions, where 400Kg has been added to the space and water heating only figures.

³The figures headed 'Space and water heating only' reflect the cost of, or carbon emissions from, the fuel used to heat the space and hot water, including any standing or fixed charges.

⁴The figures in brackets after the heating system in column 1 reflect the seasonal efficiency of the system (i.e. SEDBUK efficiency for fossil fuel boilers or its equivalent).

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