Make a list of all the equipment you run.
Record the Power consumption from the back of each transformer and the PSU.
Add them all up, and reduce the figure by 1/3rd.
Multiply this figure by the number of hours you run them each day.
Multiply this figure by 363 ~ you're not going on line over Christmas ~ Are you!
Divide by 1000.
Multiply by the cost per Kilowatt hour.
Divide by 100
Add the environmental subsidy.
Increase by 8% for inflation.
Add 17.5% VAT.
That's it ~ Simple really!