Assessing your environmental impact
Measuring the amount of emissions relating to energy use is relatively straightforward.  As with all emissions recording you should specify reporting periods and measure accurately for that period, the period usually being each calendar month.

Taking meter readings on a regular basis should only take a few moments each month.  Electricity may be partly or fully renewable.  You will know this from your bill.  Even if fully renewable we recommend that you include 10% of emissions which allows for inefficiencies in the distribution system and emissions related to manufacture and installation of generators, turbines and solar panel.  Recording 10% rather than zero also means that profligate use is avoided.

The only point to note regarding gas usage is to ensure you are working with the correct units of measure.  This can be established by reference to your gas meter or bill.

The conversion factors from meter readings to emissions are:

  • Electricity 0.43 CO2 kg / kWh
  • Natural Gas 0.19 CO2 kg / kWh
  • Butane  1.51 CO2 kg / litre
  • Propane 1.51 CO2 kg / litre
  • Oil  2.69 CO2 kg / litre
  • Coal  2.548 CO2 kg / kg
  • Wood  1.035 CO2 kg / kg

Converting other units of gas to kWh requires one of these factors:

  • 1 Therm =   29.31 kWh
  • 1 Cubic m =   10.67 kWh

Recording should include total kWh and CO2 kg.  These may also be expressed as kWh and CO2 kg per square meter of floor area (1 square meter = 10.764 square foot).

Deciding on your targets
Electricity usage best practice depends on sector and on the type of building you are in.  Examples of targets for electricity usage are 44 kWh per square meter per year for standard offices, add 40 kWh / m2 pa for air conditioning and a further 66kWh/m2 pa for a building with night storage heaters and no gas heating.

An example of a gas heating target is 59 kWh per year per square meter.

All energy usage will vary depending on temperature.  For those that are particularly keen there is a concept known as degree days that enables adjustment for the average temperature during the month.  We recommend that totals are simply recorded and then year on year averages are targeted for reduction.

Reducing your impacts
Electricity supplied with a valid Climate Change Levy Exemption Certificate should be counted as Certified Renewable.  Your supplier will be able to tell you the percentage of renewable energy used.

To reduce the amount of electricity there are some immediate steps such as turning computer equipment off at night and turning monitors off at lunch time.  No equipment should be left on standby when not in use.  Energy efficient light bulbs are an obvious next step.   Many actions will be longer term and are centred on buying equipment that is energy efficient.

It should be remembered that air conditioning is a relatively new fad in this country and many millions of workers manage perfectly well without it.  There is no legal maximum, although the TUC have called for an upper limit of 30C for non-strenuous work.  A far better solution to overheated work areas in summer is to effectively insulate your building and implement natural air cooling and shading systems.

Gas usage can often be considerably reduced by installation of more efficient boilers.  Heating controls should be temperature, time and day of week dependent.  The law on minimum temperatures is clear and unambiguous – 13C for strenuous work and 16C generally; certainly thermostats should be set at less than 20C.

Contractors and very small businesses may be able to consider wood burning to heat the workplace.  Wood is effectively a battery for solar power.  If trees are considered a temporary store of carbon (compared to fossil fuels) and your wood is from a renewable source or saved from landfill then burning wood is effectively carbon free.  However, in line with best practice we recommend accounting for 50% of emissions caused by wood burning (rather than zero) to allow for the time delay in new trees reabsorbing the carbon.

Solar panels are a cost effective way of reducing energy related emissions.  There are two main types of solar systems: water heating collectors and photovoltaic solar electric panels.  In financial terms both types offer an annual saving of approximately 3% of the investment.  In terms of environmental impacts, solar can reduce carbon dioxide emissions by up to 200kg per year for every £1,000 investment.