How to improve a commercial EPC rating

Start with the one fact that changes everything

A non-domestic EPC is an asset rating of the building and its services, not of your metered use. The assessment models the building — its fabric, its fixed services and the controls on them — and produces a rating from that model. It does not read your bills.

That single fact explains most of the confusion in this market. It is why a building can halve its energy use through better housekeeping and keep exactly the same certificate. It is why switching the lights off at night does nothing for compliance even though it does a great deal for your costs. And it is why replacing what is installed is the only thing that moves a rating.

It also explains why lighting punches above its weight. Lighting is a fixed service, it is cheap to replace relative to heating plant or glazing, and replacing it typically cuts lighting energy by a substantial margin, commonly more than half. You are changing an input the model takes seriously, for the least money and the least disruption of anything on the list.

The order to do it in

Measures have an order, and the order is set by cost per rating point rather than by size of saving. A measure that saves a great deal of money and costs a great deal of capital is a worse first move than a cheap measure that moves the rating a modest amount.

Where this goes wrong

Two failure modes, and they are opposites. The first is doing nothing until a deadline is close, then discovering that the only available route is the expensive one because the lease events you could have used have already passed. The second is spending on a large capital measure early, on the strength of a saving figure, without checking what it does to the rating in your particular building.

Both are avoided by the same thing: find out where the headroom is before you spend, and sequence the work against the building rather than against a sales call.