Environmental Information Exchange

Measuring and monitoring energy use

Understanding how much energy an organisation uses in total can be challenging. Finding out about energy used by a single appliance or process can be equally difficult. Many energy efficiency actions require a sense of the energy that will be saved, compared to the costs and effort to make those savings.  The following information can help an organisation quantify energy use and its aspects and effectively identify potential areas for making reductions.

Measuring energy use

Energy use over time is measured in kilowatt hours (kWh), though often expressed as a cost.  Electricity and gas use are measured at meters (though gas use is measure in cubic feet or metres and then converted in kWh on bills).  Other sources of energy such as oil and LPG are measured in different ways but amounts can be converted into kWh.

Ideally an organisation will know how much energy is used over a period of time (one year, quarterly, monthly, daily, or even hourly).  For this the source of information needs to be accurate and frequent (see bills).

Sources of energy use information

Source

Advantages

Disadvantages

Meters

Entirely accurate.  Meters are accessible on premises and can be recorded and provided to your energy suppliers

One single reading provides little useful information

Energy bills

Provide kWhs for readings over period of time (often quarterly) as well as associated costs

Readings are often estimated by the supplier unless they  are provided by the customer (denoted by a ‘C’)

Automatic meter readings

Entirely accurate provided at frequent intervals ranging from every month to every half hour.  Detailed analysis is often available

Not yet widely available.  In some cases there may be a charge for access to data or presentation of information in the form of graphs / charts

Monitoring energy use

The main purpose of monitoring energy use is to quantify amounts of consumption as well as identifying potential wastage through anomalies compared to usual usage. Effective monitoring also indicates progress towards reduction targets.

Monitoring actions include:

Collecting further information

Sometimes the monitoring of energy use information may not explain anomalies and further data may need to be collected.  Sometimes energy use needs to be observed directly to understand how technology or users are behaving.  Data may need to be collected on how equipment uses energy (for example the cycling of compressors for a large freezer) or details about how controls have been set.  Sometimes users may need to be engaged about their use of equipment.  Generally, the greater the knowledge and communication within an organisation, the better understood energy use is.