Retrofit Savings Estimator
Estimate the combined savings from multiple energy efficiency improvements (insulation, windows, heating, etc).
Current Annual Cost
£1800.00
Total Investment
£34800.00
Annual Saving
£2304.00
Payback Period
15.1
years
EPC Rating
Quick Win (3 measures)
Loft Insulation to 270mm
highLay 270mm mineral wool in loft
Cost
£500.00
Annual Saving
£216.00
Payback
5 yrs
EPC Gain
+12
ROI
43%
Cavity Wall Insulation
highFill cavity walls with foam or mineral wool
Cost
£1200.00
Annual Saving
£270.00
Payback
8 yrs
EPC Gain
+15
ROI
23%
Smart Heating Controls
mediumInstall smart thermostat with TRVs on all radiators
Cost
£600.00
Annual Saving
£108.00
Payback
10 yrs
EPC Gain
+5
ROI
18%
Major Upgrade (2 measures)
Air Source Heat Pump
very-highReplace boiler with ASHP (COP 3.2). Needs BUS grant consideration.
Cost
£10000.00
Annual Saving
£720.00
Payback
25 yrs
EPC Gain
+25
ROI
7%
5kW Solar Panel System
very-highInstall 5kW solar PV system with grid export
Cost
£10000.00
Annual Saving
£630.00
Payback
29 yrs
EPC Gain
+15
ROI
6%
Medium Investment (2 measures)
High-Efficiency Gas Boiler
mediumReplace old boiler with modern condensing boiler (90%+ efficiency)
Cost
£2500.00
Annual Saving
£144.00
Payback
31 yrs
EPC Gain
+8
ROI
6%
Double Glazing Upgrade
mediumReplace single/old double glazing with modern double glazing
Cost
£5000.00
Annual Saving
£126.00
Payback
71 yrs
EPC Gain
+10
ROI
3%
Premium Addition (1 measures)
5kWh Battery Storage
lowAdds to solar: increases self-consumption, enables backup power
Cost
£5000.00
Annual Saving
£90.00
Payback
100 yrs
EPC Gain
+0
ROI
2%
Do These First
- ▸Loft Insulation to 270mm
5 yr payback, £216.00/yr saving - ▸Cavity Wall Insulation
8 yr payback, £270.00/yr saving - ▸Smart Heating Controls
10 yr payback, £108.00/yr saving
Medium-Term
- ▪Air Source Heat Pump
25 yr payback, £720.00/yr saving - ▪5kW Solar Panel System
29 yr payback, £630.00/yr saving - ▪High-Efficiency Gas Boiler
31 yr payback, £144.00/yr saving
Long-Term Investment
- ●Double Glazing Upgrade
71 yr payback, £126.00/yr saving - ●5kWh Battery Storage
100 yr payback, £90.00/yr saving
EPC Rating Impact
Current Rating
39
out of 100
After All Upgrades
100
+90 points
💡 Retrofit Strategy
- Start with quick wins: Loft insulation, cavity fill, controls have best payback
- Apply for grants: Check BUS grant (£7,500 for heat pump), ECO grants, council funding
- Combine measures: Installing together is cheaper and more effective
- Improve insulation first: Before installing heat pump or solar
- Phase the work: Don't need to do everything at once
- Get professional advice: EPC assessor can prioritize for your property
- Plan for the future: Gas boilers will be phased out by 2035
- Consider package financing: Many installers offer payment plans
Ranked by Return on Investment (ROI)
Loft Insulation to 270mm
£500.00 cost, £216.00/year saving
43% ROI
5 yr payback
Cavity Wall Insulation
£1200.00 cost, £270.00/year saving
23% ROI
8 yr payback
Smart Heating Controls
£600.00 cost, £108.00/year saving
18% ROI
10 yr payback
Air Source Heat Pump
£10000.00 cost, £720.00/year saving
7% ROI
25 yr payback
5kW Solar Panel System
£10000.00 cost, £630.00/year saving
6% ROI
29 yr payback
High-Efficiency Gas Boiler
£2500.00 cost, £144.00/year saving
6% ROI
31 yr payback
How a Whole-House Retrofit Plan Stacks Up
A full retrofit is rarely a single project. It is a sequence: insulation first, then heating, then renewables. The estimator runs nine measures against your property age, type, size and current EPC, then ranks them by payback. A medium semi from 1975 to 1995 with EPC E typically shows £1,800 in current annual energy spend, with the cheapest wins (loft insulation at 270mm for around £500, smart heating controls for £600) recouping themselves inside a decade.
The ordering matters. Air-source heat pumps cost roughly £10,000 installed and only make financial sense once you have already insulated the walls and loft, otherwise the system is sized too large and runs inefficiently. The same goes for solar: a 5kW array around £10,000 pays back faster if you have a battery and a heat pump using the daytime generation, rather than exporting most of it back to the grid at low rates.
What Grants Are Available in 2026
The Boiler Upgrade Scheme (BUS) currently offers £7,500 toward an air source heat pump installation, which knocks the headline £10,000 cost down to £2,500 net. ECO4, the Energy Company Obligation, covers full or partial cost of insulation and heating measures for households on means-tested benefits or with low-income occupants in EPC D-G properties; a complete ECO4 package can be worth around £10,000 per home.
Local councils run their own grant pots through the Home Upgrade Grant and the Local Authority Delivery scheme; these change yearly and have postcode eligibility. Always check what you qualify for before paying for measures privately, because retrospective claims are usually not allowed once work has started. Use the [EPC Improvement Checker](/epc-improvement-checker) to see which improvements push your specific rating fastest.
Typical Payback by Measure (medium 3-bed, current EPC E)
| Measure | Cost | Annual Saving | Payback |
|---|---|---|---|
| Loft insulation (270mm) | £500 | £216 | ~5 yrs |
| Smart heating controls | £600 | £108 | ~10 yrs |
| Cavity wall insulation | £1,200 | £270 | ~8 yrs |
| Condensing gas boiler | £2,500 | £144 | ~31 yrs |
| Air source heat pump | £10,000 | £720 | ~25 yrs (less BUS) |
| 5kW solar PV | £10,000 | £630 | ~29 yrs |
Frequently Asked Questions
Should I get a heat pump before insulating?
No. Heat pumps run at lower flow temperatures than gas boilers, around 45 to 55°C against 70°C, so they need a well-insulated envelope to keep rooms warm. Installing one in a leaky pre-1930 solid-walled house often results in a system that struggles in cold snaps and runs constantly. Get loft insulation, cavity fill where possible, and draught-proofing done first.
How long does a full retrofit take?
A phased retrofit normally spans three to five years. Quick wins (loft, controls, draughtproofing) can be done in a single week. Cavity wall insulation is a one-day job. New boilers or heat pumps take two to five days. Solar takes a day. Solid wall insulation, if needed, is the disruptive one - allow two to four weeks. Spreading the work also spreads the cash flow.
Will gas boilers really be banned in 2035?
The current government plan is to phase out the sale of new gas boilers in new-build properties by 2025 and end gas boiler installations in existing properties by 2035. Existing boilers are not affected. If your boiler is over 12 years old in 2026, the next replacement may be your last gas-powered one, so factor heat pump readiness (insulation, larger radiators) into any boiler decision now.
What EPC rating should I aim for?
Band C (a score of 69 to 80) is the realistic target for most older homes and is the threshold for some future regulations on rented properties. Pre-1930 solid wall properties can be very expensive to push above D without solid wall insulation. Modern post-1995 builds often reach B with insulation, controls and a small renewables addition.
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