What to do and how to do it
Identify energy influencing factors
First you need to identify the factors that influence energy consumption. These may include the following:
Where energy is used mainly for heating and cooling of buildings, daily or seasonal variations in the weather will influence energy use. There should be a direct relationship between weather conditions and energy use. To quantify the influence of the “weather” and normalise your energy data, use Degree days, which gives you a measure of the severity and duration of cold weather.
Compare energy use against production levels. Increased production will usually cause increased energy use. However, this may mask the true relationship, as the lighting or heating energy use may not change much against production levels. Therefore try to separate out non-production related energy use in normalising your data.
Is your energy use consistent with occupancy? Compare usage during the week with usage at night, weekends or holidays and see if you are using energy unnecessarily outside of working hours.
In order to compare energy use over time, you need to normalise your energy consumption figures. After doing this you can identify trends in consumption and apply performance indicators to compare performance.
Having identified the factors that influence consumption and normalised your data, it is important to compare your performance against other internal or external reference standards (performance indicators) to determine how well you are actually performing.
Identify Energy Performance Indicators (EnPIs)
EnPIs can be used to develop relative measures of energy performance, track changes over time, and identify best practice in energy management. They are also a means of evaluating whether you have achieved your objectives and targets.
Establish your EnPIs using two main approaches:
- Best Practice- a comparison against established practices considered to be the best in the industry or sector.
- Past performance - comparison of current versus historical performance.
In general, best practice indicators relate to external comparisons, while past performance and other measures focus more on internal indicators.
The main steps in applying EnPIs include:
- Select the scope of the EnPI
[internal/external, best practice/past performance]
- Determine the focus of the EnPI
[building type, industrial process line, organisational wide …]
- Develop the measurement criteria that expresses energy performance in terms of a relevant activity (or activities) in your organisation
[consumption, cost, CO2, other non-technical measures, electricity, fossil fuel]
- Select the time frame for analysis.
- Obtain energy data and identify internal or external reference standards (EnPIs) for energy consumption.
- Carry out the comparisons against the standards.
- Track performance over time.
Possible problems and how to deal with them
Data quality and availability
Incomplete energy consumption or activity data and inaccurate building floor areas can result in misleading conclusions and erroneous decision making. Also there may be a lack of suitable EnPIs for your sector, building type or industry. In Ireland EnPIs may be available from SEAI. A wide range of performance indicators are also available from the UK Carbon Trust.
In industry, energy use does not always depend on production throughput. The less sensitive energy use is to production, the more sensitive the EnPI will be to changes in production.
Use EnPIs with caution. If external factors are not accurately taken into account, then the resultant EnPIs can mask actual trends in energy consumption and lead to erroneous decision making.
Poor analysis/interpretation of data
You could spend a lot of time analysing your data without coming up with usable results on the key information. Do not try to analyse every factor that may influence energy use, instead stick to the main factors and produce concise usable results.
How long does it take to complete this step?
If you have the data – energy use, degree days, production volumes, occupancy data or other factors, EnPIs – and are familiar with the techniques, then completing this step should be possible in about a day.
How do I know when I have completed this step?
You have completed this Step when you have produced:
a documented list of factors which affect energy consumption and established a system for recording and normalising variations in their levels.
Energy Performance Indicator(s) for making comparisons on energy consumption.
What do I do next?
Now that you have a good understanding of how energy is used and how it can be controlled, the next step is to identify energy saving opportunities.