Energy saving assumptions

Lighting assumptions

The saving for the average CFL is derived from Carbon Emissions Reduction Target (CERT) savings and an average electricity price of 13.95p/kWh. The higher figure reflects the saving from exchanging brighter or higher use bulbs and is an average of the savings achieved by exchanging a 60W incandescent with a 15W CFL (1,100 hours per year) and replacing a 100W with a 20W CFL (770 hours per year).

Replacing lamps of lower wattage or usage will give lower savings, though reductions in lighting electricity consumption of the order of 75% - 80% should still be expected.

Appliance assumptions

Savings assume replacing an average appliance purchased new in 1998 with an Energy Saving Recommended model of similar size and an electricity cost of 13.95p/kWh.

Appliance	EU Energy rating	Saving a year (up to)	CO2 saving a year (up to)
Fridge freezer	A+ or A++	£39	142 kg
Upright/ Chest Freezer	A+ or A++	£23	85 kg
Refrigerator	A+ or A++	£13	48 kg
Washing machine	A	£11	45 kg
Dishwasher	A	£23	90 kg
Integrated digital televisions		£7	24 kg

Heat Replacement Effect

Electrical appliances and lighting in the home give out heat when they are switched on or are on standby. In the case of incandescent lighting, about 95% of the electricity is wasted as heat with only 5% being used to provide light.

Most lights and appliances are situated in heated living spaces, where some of the energy they consume contributes to the warmth of the building. If the waste heat they emit is reduced through design improvements, the temperature inside the building can only be maintained by adding heat from another source such as a heating system. This effect is known as the Heat Replacement Effect.

Using your lighting and appliances to heat your home for instance when you may have gas central heating is not recommended. Electricity is typically four times (13.95p/kWh) more expensive than natural gas (4.03p/kWh) and emits more than twice as much CO ₂ for each unit of energy used.

Where appropriate, adjustments to account for the Heat Replacement Effect have been made in our calculations. For instance, our lighting, appliances and standby savings incorporate reductions to account for the potential increase in space heating that may be required when more energy efficient products are installed. This is the reason for the slight reduction in savings compared to previous figures.

Insulation Assumptions

The costs and paybacks shown are approximate, are provided for illustrative purposes only and based on a gas heated semi-detached house with 3 bedrooms. Savings assume a gas price of 4.03p/kWh. Some of the savings made may be taken in increased comfort.

Installed Costs and paybacks assume that installation is undertaken by a professional installer and both loft and cavity wall insulation costs include a subsidy which can be obtained under the Carbon Emissions Reduction Target (CERT). The total, unsubsidised cost of installing either loft or cavity wall insulation is typically around £500.

A variety of grants and offers are available from the government, local authorities and energy suppliers.

Measure	Cavity Wall Insulation	Internal Wall Insulation¹	External wall Insulation²	Double glazing
Annual saving (£/yr)	Around £160	Around £470	Around £500	Around £140
Installed cost £	Around £250	From £42/m 2	Around £5,600
Installed payback	Around 2 years		Around 11 years
DIY cost
DIY payback
Annual CO 2 saving	Around 800kg	Around 2.4 tonnes	Around 2.5 tonnes	Around 720kg

Measure	Loft insulation (0-270mm)	Loft insulation (50-270mm)	Floor insulation³
Annual saving (£/yr)	Around £205	Around £60	Around £50
Installed cost £	Around £250	Around £250
Installed payback	Around 1 year	Around 4 years
DIY cost	Around £300	Around £200	Around £90
DIY payback	From 2 years	Around 4 years	From 2 years
CO 2 savings	Around 1 tonne	Around 300kg	Around 250 kg

Measure	Draught proofing	Filling gaps between floor and skirting board	Hot water tank jacket	Primary pipe work insulation
Annual saving (£/yr)	Around £30	Around £25	Around £40	Around £10
Installed cost £	Around £200
Installed payback	Around 7 years
DIY cost	Around £90	£20	£12	Around £10
DIY payback	Around 3 years	1 year	Around 5 months	Up to 1 year
Annual CO 2 savings	Around 150 kg	Around 130 kg	Around 195 kg	Around 65 kg

¹Assumes insulating to a U-value of 0.45 W/m²K.
²Assumes insulating to a U-value of 0.35 W/m2²K. Installed costs are the full cost of installation £5,600 for a semi-detached house. If repairs are needed to the outside of the house then this is an ideal time to consider external wall insulation and the cost will be reduced.
³Floor Insulation represents the cost of the insulation only.

Heating assumptions

The costs and paybacks shown are approximate and are provided for illustrative purposes only and are based on a gas heated semi-detached house with 3 bedrooms. Savings assume a gas price of 4.03p/kWh.

Heating control costs assume the additional cost for installation when an installer is at the premises already working on the heating system. Savings for condensing boilers assume that their installation is mandatory due to building regulations and hence there is no additional cost when compared with a non-condensing equivalent.

Measure	Annual saving (£/yr)	Installed cost £	Installed payback	CO 2 saving a year
Condensing boiler	Around £170			Around 875 kg
Heating controls upgrade	Around £105	From £200	Around 2 years	Around 530kg