We calculate your 5 year energy estimate by taking either your full year expenditure on energy, or as much data as you have provided and extrapolating it over 5 years pro-rata. We apply a 4% inflation rate to account for the typical inflation rate of energy prices over the past decade. It might be higher or lower than this and we will adjust it occasionally to account for the best inflationary data we have available.
Investing in energy efficiency and renewable energy is a tricky business. Suppliers will promise you the sun, moon and stars when it comes to buying products for improving energy efficiency or supplying renewable energy. For this reason, it is good to see how much you are expected to spend on energy over a 5 year period and see how the changes/upgrades will reduce this.
We have seen examples of solar energy suppliers promising to reduce a companies energy bill by more than the company actually spends on energy each year! So knowing how much you spend over a 5 year period is very useful to see if there is a reasonable pay back from upgrading energy systems.
For more detailed analysis, it is best to start with the energy source you will be saving, i.e. electricity (day or night rate), gas or oil. Night electricity is typically half the price of day rate electricity, heating oil is typically a third of the price of day rate electricity and gas is typically a quarter of the price of day rate electricity. So not all energy saved is the same.