The Short Answer
Start with the cheap jobs, because they pay back fastest: the Energy Saving Trust says turning your thermostat down from 22C to 21C could save about £120 a year, a £30 cylinder jacket about £45, and draught proofing about £55. Then fill an empty cavity and insulate a bare loft, which DESNZ measured cutting gas use by a median 12% and 3.2%.
The big jobs come after: a heat pump (DESNZ's median install about £12,908, £5,408 after the grant in England and Wales) and solar panels (£6,200 to £6,600 for 4kW). At the 1 October to 31 December 2026 price cap both save money, but they take years to pay back, and grants decide whether the biggest insulation jobs make sense.
EPC Ratings, A to G
An Energy Performance Certificate rates a home from A to G on a score worked out by the government's Standard Assessment Procedure:
| Band | Score |
|---|---|
| A | 92 and over |
| B | 81 to 91 |
| C | 69 to 80 |
| D | 55 to 68 |
| E | 39 to 54 |
| F | 21 to 38 |
| G | 1 to 20 |
Our EPC improvement calculator shows what each upgrade does to the score, and the cheapest way to reach the band you want. For what the bands and scores mean, see EPC ratings explained.
Cheap and Free
- Thermostat: the Energy Saving Trust says most people are comfortable between 18C and 21C, and turning down from 22C to 21C could save about £120 a year in Great Britain (£80 in Northern Ireland).
- Heating controls: a programmer, thermostat and radiator valves cost around £600 from scratch, or £370 for valves alone, and could save around £100 a year in Great Britain (£110 in Northern Ireland), the Energy Saving Trust says.
- Hot water cylinder jacket: about £30, saving about £45 a year on an 80mm jacket over 25mm of foam.
- Draught proofing: around £250 done professionally, saving about £55 a year; blocking an unused chimney saves about £45.
Insulation
| Job | Cost (Energy Saving Trust) | Saving a year | Payback |
|---|---|---|---|
| Cavity wall | £2,200 | about £101 (DESNZ) | about 22 years |
| Loft, bare to 270mm | £750 | £27 or more (DESNZ, all loft jobs) | up to 28 years |
| Loft, top-up from 120mm | £600 | about £17 | about 35 years |
| Solid wall (semi) | £12,000 to £15,000 | about £146 (DESNZ) | 82 years or more |
| A-rated double glazing replacing single (semi) | £4,800 | about £85 | about 56 years |
DESNZ savings are its median for all homes in England and Wales applied to a semi's median gas use at today's price cap; the others are the Energy Saving Trust's. Our insulation costs guide goes job by job, and our savings calculator works it out for your house type.
Heating
DESNZ's median air source heat pump install was about £12,908 in April to June 2026, and the £7,500 Boiler Upgrade Scheme grant in England and Wales brings that to about £5,408. On our model of a three-bed home, a heat pump saves about £130 to £140 a year against gas on a standard tariff, or £300 to £320 on a heat pump tariff. Our heat pump costs guide and heat pump vs boiler calculator have the detail; if you heat with oil, the oil comparison is the one to read.
Generating Your Own
A 4kW solar system costs about £6,200 to £6,600 on DESNZ's 2025/26 figures for home installs, and on our estimate is worth about £599 a year in central England. Our solar costs guide has the detail.
The Order We'd Do It In
Our view, in order:
- The free and cheap jobs: thermostat, controls, cylinder jacket, draught proofing.
- An empty cavity and a bare loft, ideally with a grant.
- A heat pump when the boiler is due, sized after the insulation (our insulate first guide explains why).
- Solar panels whenever the roof suits, before 0% VAT ends on 31 March 2027 if you're going ahead.
- Solid walls and glazing only with a grant or another reason, such as comfort or damp.
Grants
ECO4 (England, Scotland and Wales, until 31 December 2026) helps people on certain benefits or in social housing. In England the Warm Homes: Local Grant can pay for insulation, heat pumps and solar panels for households with an income usually of £36,000 or less in homes rated D, E, F or G. Scotland has Home Energy Scotland, Wales has Nest, and Northern Ireland has Affordable Warmth and NISEP. Our grants hub has every scheme.
Frequently Asked Questions
Quick Wins for Energy Efficiency
Cheap draught proofing you can fit yourself, and a monitor to see what your home uses.
Stormguard Double Door Seal
£26.39Seals the gap around a door when it closes. The Energy Saving Trust puts the saving from draught proofing windows, floors and doors at about £55 a year.
Aluminium rebate sealFind on Amazon
Exitex Letterbox Draught Excluder
£13.98A brush cover for the letterbox, one of the gaps the Energy Saving Trust suggests draught proofing.
Fits standard UK letterboxesFind on Amazon
Chimney Sheep Chimney Draught Excluder
£33.00Blocks an open chimney you don't use. The Energy Saving Trust puts draught-proofing an unused chimney at about £45 a year saved.
Various sizes for UK chimneysFind on Amazon
OWON WiFi Smart Energy Monitor
£50.39Shows how much electricity your home, or your heat pump on its own circuit, is using in real time.
WiFi + 3x CT clampsFind on AmazonAs an Amazon Associate we earn from qualifying purchases. Prices and stock are checked against Amazon every few hours and may have changed since.
