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How GreenReporting calculates the carbon cost
A reviewer should be able to follow every figure back to an input. This page sets out the carbon cost method, the defaults, and what we have not validated.
Last reviewed 14 October 2026. Not financial, legal or regulatory advice.
The method
- Start from your baseline emissions in tonnes of CO2e a year.
- Grow them by the annual rate you choose. The default is 2%, applied from year 1.
- Multiply each year's emissions by the carbon price, held constant in today's terms.
- Discount each year's cost to today at your discount rate, 8% by default, with costs falling at year end. The sum is the present value.
In symbols: for year t, emissions Et = baseline × (1 + g)t, cost = Et × price, and present value = cost ÷ (1 + r)t. The present value of carbon cost is the sum over the horizon.
| Year | Emissions (tCO2e) | Cost ($) | Discount factor | Present value ($) |
|---|---|---|---|---|
| 1 | 8,160 | 530,400 | 0.9259 | 491,111 |
| 2 | 8,323 | 541,008 | 0.8573 | 463,827 |
| 3 | 8,490 | 551,828 | 0.7938 | 438,059 |
| 4 | 8,659 | 562,865 | 0.7350 | 413,722 |
| 5 | 8,833 | 574,122 | 0.6806 | 390,738 |
| 6 | 9,009 | 585,604 | 0.6302 | 369,030 |
| 7 | 9,189 | 597,317 | 0.5835 | 348,528 |
| 8 | 9,373 | 609,263 | 0.5403 | 329,166 |
| 9 | 9,561 | 621,448 | 0.5002 | 310,879 |
| 10 | 9,752 | 633,877 | 0.4632 | 293,608 |
| Present value of carbon cost | 3,848,668 | |||
Defaults and limits
Defaults
2% a year emissions growth, an 8% discount rate and a 10 year horizon. Every one is an input you can change.
Carbon price
Held constant in today's terms. The report also runs sensitivities, including a price rising 4% a year.
Timing
Each year's cost is discounted as if it falls at the end of the year.
Intensity
Scope 1, 2 and 3 emissions divided by revenue in millions of dollars.
Benchmarks
Sector intensity benchmarks are internal estimates. They do not yet state which scopes they cover and are not matched to a licensed dataset.
Not covered
This page covers the carbon cost and intensity figures. Other report calculations are described in Appendix A of each report.
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