Why can't we just use numbers? "This house in this climate will use about X kwh per year for heating/cooling". That's what appliances do. No messing with scales and tiers and having to constantly re-balance.
It's also more directly meaningful to customers. An A+++++ mansion is going to use more energy to heat than a modest A+++ house.
Because numbers require everyone who is involved in comparing options (i.e. consudmers) to have intimate knowledge of what those numbers mean. Is X kwh actually good? How does it compare to other houses in the area? What number do you use - the amount of energy it will take to heat the house, or the amount of energy of a specific type you will use. How do you compare those (a house with Natural Gas as a heat source will require significantly less electricity to heat than a house with electric radiators, but will likely _cost_ more).
Using ratings gives a standardised way to compare them. If you compare two houses, one has an A rating and one has a B rating, the B one is strictly worse, by an amount that someone who knows something about this has deemed significant.
> That's what appliances do
Appliances are graded on a similar score here. Every appliance you buy in the EU has one of these [0] labels (which has the same problem).
> An A+++++ mansion is going to use more energy to heat than a modest A+++ house.
You're comparing two different things here, and forgetting a very important point - someone who is going to buy a "mansion" is not going to buy a modest house, so it doesn't matter what the rating of the house is in comparison. What matters is the rating of the mansion next door.
Hm, in the US we have energy labels on appliances like [1] that just tells you how much energy it will likely use. When shopping for a fridge, you can directly compare different models.
It even shows the average cost of other similar products. So you can see both the absolute numbers and a visual representation of how efficient something is in relative terms without having to squint and count '+' marks.
I don't see why we couldn't do that for houses. Maybe use a unit like BTU instead of kwh to account for different heating sources. And include a comparison to the average range for houses in the area.
This would be a lot more concrete and avoid arbitrary ratings. If the ratings are based on bureaucratic rules (i.e. can't have stovetop vents) instead of actual measurements, then it feels a lot less meaningful. "This house will cost about $X to heat each year" is a much more useful piece of information for someone house shopping.
We can, don't have them on hand though. There's still a huge number of houses with B or lower ratings, so I only if you're looking at new builds do you have to count plusses ;)
It's also more directly meaningful to customers. An A+++++ mansion is going to use more energy to heat than a modest A+++ house.