Review historical energy use
Reviewing your historic energy use costs little but can be invaluable for finding ways to cut your energy use. And the information you’ll need is usually at hand within your organisation’s electricity and fuel accounts.
- Energy performance indicators
- Reviewing your energy accounts
- Data you need to factor out
- Comparing energy pricing
- Advanced analysis tools
- Expert audits
The energy used by any business varies as production processes, volumes and inputs vary. Finding the relationship between your energy use and energy performance indicators lets you determine:
- if your current energy use has improved
- energy consumption trends that reflect operating patterns
- how much your future energy use might change aspects of your business
- areas your business wastes energy
- comparisons with similar businesses
- how your business has reacted to changes in the past
- how to develop performance targets for your energy management plan.
Start by assembling all your energy accounts for the last 2 years. Be aware that there may be a number of rates, depending on the way your business buys energy.
You may need to factor out changes that are beyond your control, such as weather conditions or operational changes caused by seasonal demands. Factor out:
- seasonal output variation by dividing energy by actual output
- production demand changes by dividing energy by actual output
- space heating and cooling loads by dividing energy by weather data, available from NIWA (National Institute of Water and Atmospheric Research).
Calculate the Energy Use Index (EUI), which is total energy use divided by floor area of a building, or divided by production. Plotting this and other variables on graphs is the clearest way to share the information with your staff. Some energy managers add a second vertical axis with production data to their energy use plots.
By developing simple models of total energy cost you can assess the real costs of alternative energy sources. For example, compare how much energy it takes to fuel a boiler using coal and gas.
Energy purchase costs are not the only costs involved in this analysis. Some types of energy have additional on-site handling costs, or energy conversion and distribution costs, for example from coal to steam to a final process. Only when you have the information that you get from an analysis of your historical energy use will you have the information you need to make informed choices.
Doing statistical analysis of your data gives you an added level of information. The sort of statistical procedures that can help you - available on spreadsheet programs - include regression analysis and CUSUM (cumulative sum difference) analysis.
If you spend more than $150,000 per year on energy, consider having a third party conduct an energy audit. Although in-house audits may keep costs down, the people undertaking the audit often lack the necessary skills.