Reporting Principles

We have used the following criteria to prepare and compile data in this report:

Inclusion principles

This report covers the calendar year ending Dec. 31, 2004. In some cases in our text, we have also reported on significant items in early 2005.

We report EH&S data for generating facilities for which TransAlta holds the operating permit, regardless of financial ownership. We do not report data from facilities or operations discontinued during the calendar year. For facilities or operations purchased during the calendar year, we report the entire year’s performance.

The following facilities will not be reported in this statistical summary but may be reported in TransAlta’s 2004 Annual Report:

• Genesee 3 expansion, Alberta (under construction in 2004; permit to be held by EPCOR and TransAlta)
• Imperial Valley geothermal assets, California (operating permit not held by TransAlta)
• Poplar Creek plant, Alberta (operating permit not held by TransAlta)
• Power Resources Inc., Texas (operating permit not held by TransAlta)
• Saranac plant, New York (operating permit not held by TransAlta)
• Sheerness plant, Alberta (operating permit not held by TransAlta)
• Yuma plant, Arizona (operating permit not held by TransAlta)

Reporting of financial performance is based on the proportion of financial ownership. Megawatt hours used to calculate EH&S data in this report differ slightly from electricity production reported in our 2004 Annual Report.

Reporting entity

We report our activities corporately and by country. We cover direct operational impacts and do not include supply chain impacts such as emissions from product suppliers.

Reporting scope

We discuss achievements that result directly from our actions. We report performance frequently through totals and ratios. We use total emissions to show environmental impacts. We use emission intensity rates (for example, emissions per megawatt hour) to measure our operations’ efficiency in controlling emissions.