How can I audit my household energy use?

A simple way of getting started is to keep a log of your gas and electricity meter readings on a weekly basis. This allows you to see the effect of any changes you make, such as adding insulation or taking draught-proofing measures.

There are also several tools that you can use to conduct a basic energy audit, and give you a good idea of what measures you need to take to improve the energy efficiency of your home and the financial savings that you could make. There are also professional energy efficiency consultants who can carry out a household audit.

Space heating

Over 80% of the energy use in an average home is for space heating and hot water - so it's most important to address this heating demand first. The Energy Saving Trust (EST) Home Energy Check requires information that you can easily work out, such as the number and approximate size of rooms, insulation levels, and single or double glazing. If you do not know, you may need to check how thick the insulation is in your attic and if you have solid or cavity walls. It gives advice on suggested renovation work, and shows the amount that bills could be reduced by and the tonnes of carbon that could be saved.

Electricity use

You'll find your total electricity use on your meter or your electricity bill. For homes that don't have electric heating the average will be about 3,600kWh (a kWh is the standard electrical unit).

Energy MeterYou can assess the energy consumption of different appliances with a basic energy meter that plugs into a mains socket, with the appliance to be tested plugged into the meter. Both instantaneous power consumption and cumulative energy use can be monitored. You can do this for each appliance (oven, washing machine, computer, electric kettle, hair dryer, iron, etc), record energy use in operation and when on standby, and multiply by the average number of hours the appliance is on each day.

To measure electricity used by lighting: for each bulb in your house estimate the number of hours it is switched on each day and multiply this by the wattage. Divide by 1,000 for the kWh used. For example, 3 hours of a 60watt bulb uses 0.18kWh.

As your appliance and lighting use is likely to vary throughout the year, it is more accurate to make separate summer and winter estimates. To get the full household electricity use, include all electrical appliances. Multiply summer and winter weekly totals by 26 to get an estimate for each season, and add these to get the full year total.

Your electricity audit will show you exactly where you can lower your electricity usage. You may be able to make some changes immediately, such as switching off appliances at the wall rather than leaving them on standby or changing to energy saving light bulbs.

Light BulbFor example, two 100-Watt bulbs on for 2 hours per day in summer and 6 hours per day in winter will use about 290kWh per year. At an average of 15p per kWh, that will cost you £43.50. Replacing those 100W bulbs with 20W CFLs (compact fluorescent lamps) would reduce this cost to £8.70 per year. And the CFLs also have a much longer lifespan.

You might also find that you can save money by replacing old appliances with newer more efficient ones that would quickly pay for themselves. The worst offenders in the typical household are:

  • lighting – 20% of electricity consumption
  • cold appliances – making up another 20%
  • appliances left on standby – responsible for 8 to 10% of average household electricity use

Energy Performance Certificates (EPC)

All properties (homes and commercial & public buildings) now need an Energy Performance Certificate (EPC) when bought, sold, built or rented. The EPC tells you how energy efficient a home is on a scale of A-G (A being the highest). There are two ratings:

  1. The energy-efficiency rating indicates a home’s overall efficiency. The higher the rating, the more energy-efficient the home is, and the lower the fuel bills are likely to be.
  2. The environmental impact rating indicates a home's impact on the environment in terms of carbon dioxide (CO2) emissions - the higher the rating, the less impact it has on the environment.

EPC rating chartEach rating is based on the performance of the building itself, relating to the construction materials and insulation, and services such as heating and lighting - but not domestic appliances. The certificate also lists the potential rating of the building if all the cost-effective measures were installed and includes recommendations on ways to improve the home's energy efficiency to save you money and help the environment. The average property in the UK is in bands D-E for both ratings.

Households that take up offers under the Carbon Emissions Reduction Target (CERT), such as insulation and heating system offers from utilities suppliers, are given energy audits. It’s also possible to hire a freelance consultant to carry out a home energy audit for you. For an average house, the cost should be about £100. More information about Energy Performance Certificates, and how to find an assessor, is available from the Government Direct website.

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