What is the best way to get my properties to an EPC rating of C?

An EPC registered surveyor etc would do a full report and advice, to your particular circumstances. But obvious things - get rid of panel heaters, syut down water heaters and install GCH. You may be able to give up a room somewhere and add GCH once for the whole building. This may need you to include bills in the rental. But that comes with its own issues sometimes. The other thing I would suggest is solar. Now if you own the whole property including the roof and roof space, you might be able to add enough panels to supply the whole property which will offset any other costs relating to GCH installation or heat pumps. But all of these are expensive, relatively. The other smaller things again depending on your circumstances are make sure all light bulbs are LED, low wattage, install water heater jackets if you still wish to keep them and I'm sure there are a few other insulation internal and external things you can do. But in summary, and as your question doesn't give enough real info GCH, Heat Pumps or Solar are expensive, but your in the same boat as most of us.
I'm only a landlord and am not hopefully treading on professionals toes with my statement, im not an EPC expert but these are what I've experienced. I'm slowly getting EPC upgrades done......slowly I'm afraid.

I would suggest you wait and see if/ when the requirements are going to be implemented. There is a good chance this will be postponed/ delayed/ amended/ cancelled so personally I’m not doing any further improvements until I know what is gong to be legally required. I know that many landlords are pre-empting in order to be ready and that’s absolutely fine too, it’s ultimately a personal / business decision.

Lawrie - you note the properties purchase in 1990's, trusting you have renewed the EPC since! Whilst the recommendations on the report give some indication of the potential improvements these are auto-generated so far better to engage a DEA who is willing to identify and model a number of other potential improvements so you can plan ahead. Be aware that an EPC produced some years ago will potentially have a different rating than one produced under current version of RdSAP, and again may be different next year when the next version of the software is due to be introduced.

I suggest you read the suggestions on the EPC. You may find this site useful https://www.gov.uk/improve-energy-efficiency in working out what you need to done next. It gives you suggestions like any EPC. My preference is for Led lighting which I presume you have. Solar PV with batteries will give you useful points and help you get over the break point between a D and C.

The EPC is based on the cost, which is at variance to the Gov's drive towards carbon Zero. As was pointed out recently, by an EPC inspector, all electric only properties are likely to be deducted some 13 points come December 2023.

You may want to hold on to see if you can get an exemption due to the age and structure of the building.

Failing that, you're going to have to look into serious loft insulation, under floor insulation, ideally on each floor. Which is likely to get you involved in modern fire retardant plaster board replacement between floors. Internal wall insulation, beware of trapping damp and avoid cheap cowboy firms.

If your still not band 'C', then solar with or without a battery rack and ground heat pumps. Be aware that ground heat pumps operate at lower temps than gas heat systems so often require 50% larger radiators in each room.

As a first step, I'd find a decent EPC inspector, one who is realistic and experienced, not a recently qualified/transferred from another role person. Then, once you have their report, discuss with them what would and would not be the most effective way to get you were you need to be.

As a final happy thought, GOV have been suggesting that they want every building to be at EPC level 'B' in the not too distant future. Quite how they are intending to improve older house stock to that level is a moot point.

Let me give you a useful tip that works.
Search on Government website for EPC rating of other similar properties, in your street.
Look for those houses that have poorest rating and scroll down and look for the Assessors name, avoid engaging those Assessors as they may be incompetent or biased or simply too harsh in taking their decision to input data into their software that decides what rating you will get, end of the day it is the Assessor who puts wrong data in. Simple as that.
So then look for all those houses that have C rating, scroll down and see what those houses have like thickness of loft insulation, Gas fired central heating, Temperature controlled Radiator valves, room thermostat and central heating programmer, a condensing boiler,
No problem if you have no external wall or cavity wall insulation obviously these are 1930 houses, and all LED lighting 100%, and so compare these items with your houses, bring your houses to those standards, even with 100mm loft Insulation I got C rating, so now the final trick is to scroll down further to see who the assessors were, note their names and contact numbers, give them a call and you are bound to get a C rating by reminding them that similar properties have achieved C rating so no reason why yours should not be given a C rating.

So if Government forces alll houses to be rated at B, this still gives you room for further improvement such as 270mm loft insulation, Heat pump source for central heating, Solar panels, etc, external or internal wall insulation, you could even reach A.

Reply to the comment left by York student landlord at 10/07/2023 - 09:58
I totally agree!!

This EPC C rating proposal will be delayed.

I forgot Double Glazing all around also scores good points. Draft proofing, but you discuss everything with your Assessor before he starts, remind him how you chose him, and you have studied similar properties in your street where this particular Assessor has given C ratings, so this would ensure he treats your property no different to others he has given C ratings.

Reply to the comment left by Jireh Homes at 10/07/2023 - 10:09
The point made by Jireh Homes is VERY important.

"Be aware that an EPC produced some years ago will potentially have a different rating than one produced under current version of RdSAP, and again may be different next year when the next version of the software is due to be introduced."

Basically, what scored, say, 80 in 2010 will not score 80 today as the goalposts have moved (with good reason) due to general improvements in heating systems, insulations and lighting.

I wondered if the reason for a drop in rating was due to boilers losing efficiency over time, but that is not the case.

Do nothing at all. This whole “C” is a shambles, until there is clarity keep your hard earned cash.