What to do and how to do it
Identify types of energy used, account numbers and meters
Identify your sources of energy: electricity, natural gas, LPG, oil, diesel or other.
Check invoices to confirm your suppliers, account numbers and associated meters. Confirm the number of meters and their location. Use the SEAI Analysing Your Bills flowchart to check your energy bills.
Quantify energy use
Quantify your use of energy and its cost, at regular intervals, e.g. at least monthly. Do this by reading meters or recording fuel consumed, e.g. litres of oil, and convert to kWh. If you don’t have meter readings, then check your bills for up to three previous years. Use the Energy Bill Tracker tool to enter your data and identify trends in energy use and any seasonal variations.
If you do not have all the invoices, then request them from your energy supplier. Many electricity suppliers make historical usage and cost data available via the internet, for downloading in tables with associated charts. However, the best solution is to make your own readings.
Try to get an overview of the main end uses of energy, e.g. lighting, drying, pumping, air conditioning, or other. However, this will be developed in further detail in Step 7.
Tip: Don’t spend too much time on smaller accounts. A quick glance through the bills should help establish which accounts are significant, or your finance section may be able to give a summary of annual energy costs for each account.
Tip: To establish annual usage of a smaller account simply get the meter reading from two bills twelve months apart and subtract one from the other. To establish the annual cost of a smaller account, multiply annual usage by the Average Unit Price from the most recent bill. Average Unit Price = total annual cost / total units consumed.
Possible problems and how to deal with them
VAT can be included or excluded, but you must be consistent.
Units of energy
Different types of energy are measured in different units. Where possible use kilowatt-hours (kWh) and convert all energy units to this unit. A conversion tool is available from SEAI.
Estimated readings, often denoted with an “E”, are not reliable. In the case of electricity and gas it is better to use the average of actual readings.
Average kWh per billing period = (Most Recent Actual Reading – Previous Actual Reading)/Number of billing periods between actual readings
Average kWh per billing period = (Most Recent Actual m3 Reading – Previous Actual m3 Reading) x conversion factor /Number of billing periods between actual readings
For oil/LPG stick with annual readings by summing individual deliveries over the year. If the tank is filled on each delivery, it is possible to calculate energy use per day by dividing the delivered volume by the number of days between fills.
How long does it take to complete this step?
For a typical site, with a single electricity and gas meter, this step can be completed in two hours if historical electricity and gas invoices/data is readily available.
For sites with a number of meters, or multiple sites, the process can be quite time-consuming and it is essential to work smart by quickly assessing usage on smaller accounts and focussing attention on the larger accounts.
Data collection is often the most time-consuming aspect, and may take several days or more.
How do I know when I have completed this step?
You have completed this Step when you have physical or computer records of:
- the different types of energy you consume, and associated account details;
- the location of meters;
- how much of each energy type you are using per year, and its cost;
- graphs or tables showing (at least) monthly energy usage from bills or own readings for up to 3 years.
- trends in overall consumption and possible causes;
- the average price per unit of each type of energy and for each site, noting differences between energy types and sites, and the reason for any differences.
What do I do next?
Now that you have a good overview and understanding of energy supply to your facility, the next step is to identify the key factors influencing your energy consumption and then to establish what equipment/plant inside the facility is using all this energy. In the next step you’ll leave the desk and go walkabout.