It would be better to have all houses by default be "unrated" and let the market decide if they want rated houses - if there is the demand landlords will pay for the report and provide the rating (at a cost built into the rent).
The silly thing with this report is that it wouldn't take to many changes to the home to drastically change the rating - would be then have to pay for a new report? Not to mention the end energy usage is very dependant on how the occupants use the appliances in the home.
The reality is this sort of thing is another unworkable bureaucratic solution.
