A marginal abatement cost curve – or MACC – is simple to understand when you break it down.
In this context, ‘abatement’ means ‘reducing’. A MACC presents the costs or savings expected from different opportunities, alongside the potential volume of emissions that could be reduced if implemented. MACCs measure and compare the financial cost and abatement benefit of individual actions. They use the metric of dollars per tonne of carbon dioxide equivalent – usually represented as $/tCO2e.
Each different opportunity is an action, presented as a box above or below a horizontal axis.
Boxes seen above the axis indicate there is a cost to that action – the higher the box, the higher the cost. Boxes seen below the axis line indicate a saving from that action – this time the lower the box, the greater the saving. So we can compare actions, these costs or savings are annualised.
The width of the box indicates the action’s potential volume of reduction per year, expressed as tCO2e.
The curve shape is created by ordering the actions from lowest cost to the left, to highest cost on the right.
Examples of abatement actions include implementing renewable energy (such as wind and solar) and storage, improving building efficiency, industrial process upgrades, renewable electrification of transport, carbon forestry and many more.