Ask ten landlords what it takes to move a rental from EPC D to C and most will give the same answer: a lot of money and probably a heat pump. The honest answer is that it depends entirely on the property, and the range is far wider than people expect. Two real examples make the point. Both rentals reached a C. One did it with a couple of cheap, targeted steps. The other needed a good deal more. The difference was not luck. It was where each property started.
The high D that needed almost nothing
The first was a semi-detached house in Greater Manchester, sitting on a D with a score of 67. That is a high D, only two points under the 69 you need for a C. Its airtightness had never been measured, so the assessment simply assumed the worst case figure of 15. A measured air test came back far better than that, which corrected a value the certificate had been guessing at. Topping up the loft from 100 mm to 300 mm did the rest. Two modest, low cost steps, and the property crossed into a C. We wrote that one up in full in a separate case study.
The mid D that needed real work
The second was a house in south London, and it started in a very different place: a D with a score of 59. That is not a high D. It is squarely in the middle of the band, eleven points below a C. No single measurement closes an eleven point gap. A property starting there needs a broader set of improvements to gain that many points, and that is what it took. The result was a jump to a C with a score of 70, and because the new certificate was lodged now, it is locked in as compliant until 2036. Same destination. A much bigger journey.
The starting score decides the route
Put the two side by side and the pattern is obvious. A high D sitting a point or two below the line is often a cheap, targeted job, sometimes just correcting values that were assumed rather than measured. A mid D is a bigger piece of work, because there are simply more points to find. The trouble is you cannot tell which one you have by looking at the house. Two properties on the same street, the same age, the same layout, can sit at 59 and 67 for reasons that are invisible from the pavement. The certificate is what tells you, and it is where any sensible plan starts.
Why you should never assume the expensive route
This matters because of money. If you assume every D needs the full retrofit, you either overspend on a property that needed a fraction of it, or you put the whole thing off because the imagined bill is frightening. Reading the certificate first tells you which kind of property you have. Some are a quick, cheap correction. Some genuinely need the bigger work. Most landlords never check, and end up either spending too much or doing nothing at all.
What both had in common
Only one thing, and it is the thing that matters most. Both reached a C, and both were lodged now, under the current rules, which means both are compliant well ahead of the 2030 deadline and locked in for the full life of the certificate. However different the routes, the outcome is the same. Sorted, and sorted early.
What this means for your portfolio
If you have several D-rated rentals, do not assume they all need the same thing, and do not assume they all need a lot. Read each certificate, work out the cheapest honest route to a C for that specific property, and lock the Cs in while the current rules still apply. Some will be quick. Some will not. You will not know until you look.
Find the cheapest honest route for your rentals
Thermova helps landlords across England and Wales work out the cheapest honest route to EPC C for each property, with measured data rather than guesswork. On the air test itself, our terms are simple. EPC C or no fee, subject to our published terms. Send us your D-rated addresses and we will tell you, free, which ones are close and what each would take to get over the line.
- Book a free check: thermova.uk/epc-compliance
- EPC D to C Case Study: how a Greater Manchester semi reached C with a loft top-up and a measured air test
- Lock In Your EPC C Before 2030: why the date you reach C matters as much as the score
- Why Your EPC Score May Be Wrong, for how assumed values pull a rating down
- How Much Does It Cost to Get an EPC From D to C, for every route compared
Frequently asked questions
Do I need a heat pump to reach EPC C?
What is the cheapest way to improve an EPC rating?
Why do two similar houses have different EPC scores?
How do I know which route my property needs?
How long does a C last once I reach it?
Is it worth doing before 2030?
Both examples are drawn from real Energy Performance Certificates on the public register. The Greater Manchester property is written up in full in a separate case study. The address and certificate references of the south London property are withheld at the owner's request, and this article does not detail its specific improvement works. General information, not advice.