Consider all running costs over the life of equipment or a process. These may include

• energy e.g. electricity, gas, transport fuel
• materials e.g. consumables, maintenance, water, waste disposal
• labour for operation, maintenance and administration.

Many investments in reducing greenhouse emissions involve an up-front expense balanced by future savings in operating costs, so it's vital that you specify a suitable lifetime over which savings can be calculated.

For example, the price premium to buy high-efficiency electric motors can be recovered quickly, with a motor typically using energy valued at 10 times its capital cost in each year of operation.

If you fail to consider future savings it can cause a worthwhile emissions reduction measure to be rejected.