Your EPC says to start with wall insulation. You probably shouldn't.

Pull up any EPC for a property below a C rating and look at the improvement steps at the bottom. There's a good chance step one is internal wall insulation at somewhere between £4,000 and £14,000.

That ordering isn't a mistake, but it also isn't advice about what you should do. It's worth understanding why, because it's costing landlords real money.

What the list is actually for

Every certificate has two ratings on it. The one you've got now, and the one the property could reach if you did everything sensible to it. That second number is the "potential" rating, and it's usually a B, sometimes an A.

The improvement list is the route to that potential rating. It's ordered roughly by impact, so the heavy fabric measures come first because they move the score the most.

Nowhere on the certificate does it mention a C, or 2030, or the fact that the law only asks you to clear one particular line.

So you get handed a route to a B when you needed directions to a C rating.

An example

Here's a real shape of the problem, using a D-rated terrace scoring 64. It needs 69 to be a C, so it's five points short.

The certificate lists:

Step	Measure	Cost	Points
1	Internal wall insulation	£4,000 - £14,000	+12
2	Floor insulation	£800 - £1,200	+3
3	Low energy lighting	£15	+1
4	Solar panels	£3,500 - £5,500	+8

Work down that list from the top and you do step one. It costs somewhere around £9,000 in the middle of the range, it gets you to 76, and you're compliant.

But look at step four. Solar on its own is +8 points, which takes you to 72. Also a C, also compliant, for about £4,500.

Same legal outcome. Roughly half the money.

Why this happens so often

The heavy fabric measures nearly always sit at the top of the list because they do the most for the score. They're also nearly always the most expensive things on it.

So the first item is usually the biggest cheque, and if you only need a handful of points there's a decent chance something further down gets you there on its own.

It won't always work out that way. Sometimes the expensive measure is genuinely the only thing that shifts the needle far enough, and on a really poor property you'll need most of the list regardless. But it's worth checking before you commit.

The honest caveat

Certificates publish a running total, not the value of each measure on its own. You get the score after step one, then after steps one and two, and so on.

That means working out what any single measure is worth involves taking the gaps between the steps, which ignores the way measures interact. Insulating the walls changes what a new boiler is worth.

So treat any number worked out this way as a good estimate rather than gospel. If you're about to spend five figures, a proper assessment is worth the money.

What I'd do

Get quotes against the cheapest route that clears a C rating, not the route printed on the certificate. And get three of them, on exactly the same scope, so you're comparing like with like.

If an assessor or installer tells you the order on the certificate is a legal requirement, it isn't. The requirement is the band.

One more thing worth doing before you spend anything. Have a look at the features table on your certificate and see how many say "assumed". Assessors mark things as assumed when they couldn't inspect them, and an assumed solid wall on a property that turns out to have a cavity can be the difference between a big bill and a small one.

You can put a postcode in here and we'll show you the cheapest combination that clears a C rating, next to what the certificate's own order would cost.