Question

How do you calculate the energy efficiency of a building?

Answer 1

`"energy efficiency"=("useful energy")/("total energy")`
Multiply result by 100 for a percentage.

Explanation:

For a building, the `"total energy"` is the total amount of energy supplied to the building. The `"useful energy"`, is the amount of energy from that which is put in, which is used in a useful manner, or in other words, isn't wasted.
If you have access to the appropriate data then this should be simple to calculate.