Site Prices Update
Last Updated28th June 2022
All calculations on this site are based on current fuel prices, they are checked regularly and calculations are automatically updated.
The costs calculated based on these fuel prices should be regarded as 'good estimates', given that fuel prices vary in different parts of the county and at different time of the year.
The calculations also have different levels of accuracy depending on the nature of the calculation. For example calculating the energy use of a known power output TV is very easy compared to calculating the effect on energy savings when insulating a cavity wall.
Site Calculations
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At Confused About Energy we aim to provide practical, impartial advice on all aspects of energy usage, climate change and ways to save money on energy bills.
All calculations on this site are based on current fuel prices they are checked regularly are automatically updated and were last changed on:-
28th June 2022
The costs calculated based on these fuel prices should be regarded as 'good estimates', given that fuel prices vary in different parts of the county and at different time of the year.
The calculations also have different levels of accuracy depending on the nature of the calculation. For example calculating the energy use of a known power output TV is very easy compared to calculating the effect on energy savings when insulating a cavity wall.
Site Calculations
| Electricity | £0.271 per unit (1 kWh) |
| Economy Electricity | £0.094 per unit (1 kWh) |
| Gas | £0.072 per unit (1 kWh) |
| Domestic LPG | £0.122 per unit (1 kWh) |
| Heating Oil | £0.104 per unit (1 kWh) |
| UK Grid CO2 Emissions | 0.233 kg per kWh used |
The main units used in this site are in the table below, For a complete explanation of power and energy Read More.
| Unit | Name | Detail |
|---|---|---|
| W | Watt | Unit of Power |
| kW | Kilowatt | 1000 watts |
| kWh | Kilowatt hour | Measure of Energy |
| L | Litre | Measure of Volume |
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If you have a very old house with solid walls then you are losing a lot of heat through the walls. Solid walls transmit heat at, at least twice the rate that uninsulated cavity walls do.
|
Cost: High
ROI: 9.4 Years
Skill: Specialist
Energy Saving: High
CO2e Saving: High
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ROI is the time it takes to return the investment in fuel savings for an average gas heated 3 bed semi-detached house and assumes no government incentive schemes are used: Years
How easy this is to do: DIY-Easy : DIY-Skilled : Specialist
How much energy will be saved with this measure: Low : Medium : High
How much Carbon Dioxide emission will be saved with this measure: Low : Medium : High
Throughout the heating and insulation section of this site an average house is used and assumes that the walls have cavities, such that a three bed house with no insulation measures, is approximated to use 20,000kWh per year and the 5 bed house is approximated to use 30,000kWh. With a solid wall house the starting point is higher about 20% higher. So for this section we will use the numbers 24,000kWh for the smaller house and 36,000kWh for the larger house for the calculations.
There are two types of insulation for solid walls, external and internal. They are both expensive and both have their pros and cons, the energy savings trust has a good list of these on their site, they seem only to consider the savings if you are gas heated however (we assume). The main problem with internal insulation is the disruption to the house and the fact that your rooms will end up being a bit smaller, if however you are planning to redecorate it may be an idea. With the external wall insulation the whole house is likely to alter in appearance, this may be an advantage to some!
With external solid wall insulation you can reduce your energy bill for heating by about 45%, and for internal solid wall insulation by about 40%. The first table calculates the approximate pay back times for external solid wall insulation and assumes an installation cost of £ 11,000 for the smaller house about £ 15,000 for the larger house. The second table calculates the approximate pay back times for internal solid wall insulation and assumes an installation cost of £ 7000 for the smaller house about £ 11,000 for the larger house
External Solid Wall Insulation
| Approx % energy saving | Approx energy saving per year |
Gas |
Electric (Std) | Economy 7 | LPG |
Fuel Oil |
|
| 3 bed house | 45% | 10800 kWh | £ 777.6 | £ 2926.8 | £ 1015.2 | £ 1317.6 | £ 1123.2 |
| Payback time with external wall insulation costing £ 11,000 (3 bed house) | 14.1 years | 3.8 years | 10.8 years | 8.3 years | 9.8 years | ||
| 5 bed house | 45% | 16200 kWh | £ 1166.4 | £ 4390.2 | £ 1522.8 | £ 1976.4 | £ 1684.8 |
| Payback time with external wall insulation costing £ 15000 (5 bed house) | 12.9 years | 3.4 years | 9.9 years | 7.6 years | 8.9 years | ||
| Calculations assume the energy required to heat an un-insulated solid wall 3 bed house is 24000 kWh and a 5 bed house is 36000kWh. | |||||||
Internal Solid Wall Insulation
| Approx % energy saving | Approx energy saving per year |
Gas |
Electric (Std) | Economy 7 | LPG |
Fuel Oil |
|
| 3 bed house | 40% | 9600 kWh | £ 691.2 | £ 2601.6 | £ 902.4 | £ 1171.2 | £ 998.4 |
| Payback time with internal wall insulation costing £ 7,000 (3 bed house) | 10.1 years | 2.7 years | 7.8 years | 6 years | 7 years | ||
| 5 bed house | 40% | 14400 kWh | £ 1036.8 | £ 3902.4 | £ 1353.6 | £ 1756.8 | £ 1497.6 |
| Payback time with internal wall insulation costing £ 11,000 (5 bed house) | 9.4 years | 2.5 years | 7.2 years | 5.6 years | 6.5 years | ||
| Calculations assume the energy required to heat an un-insulated solid wall 3 bed house is 24000 kWh and a 5 bed house is 36000kWh. | |||||||
Is it worth doing?
Of the various insulation measures outlined on this site, this is probably the least cost effective simply because of the costs of installing it. The external insulation is more expensive and will require professionals to do it, so there are unlikely to be ways to reduce costs. With the internal insulation a competent DIY'er may be able to do the job and as such reduce the payback time. With expensive heating fuels the measure becomes more sensible for example if you use LPG or heating oil. The measure does however represent and enormous energy saving and corresponding reduction in C02, if this is a concern to you, and remember fuel prices are only going up!
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