Calculate loft insulation savings and payback
Enter the installation cost and expected annual saving. The calculator estimates the payback period, 5-year net saving and 10-year net saving for loft insulation.
Installation cost of £930 with expected annual saving of £340.
Insulation depth check
Loft insulation payback formula
Payback compares the upfront installation cost with the annual energy bill saving. The 5-year and 10-year figures show savings after the upfront cost has been deducted.
payback years = installation cost ÷ annual saving
5-year net saving = annual saving × 5 - installation cost
10-year net saving = annual saving × 10 - installation cost
Current depth vs target depth
The calculator includes a depth check because savings depend heavily on how much insulation is already in the loft. Energy Saving Trust notes that if current insulation is around 120mm, increasing it to 270mm — the minimum recommendation for new builds — could still save money on bills.
If your current depth is already close to target, the additional saving may be lower than a home with little or no loft insulation.
How much could loft insulation save?
Savings depend on property type, current insulation, heating system and energy prices. Which? says loft insulation could reduce bills by up to £340 per year depending on the home.
Higher potential
Homes with little or no loft insulation usually have the most room to improve.
Moderate saving
Topping up older insulation can still help, but savings may be smaller.
Check first
If depth and coverage are already good, other upgrades may matter more.
What affects loft insulation savings?
The calculator is only as good as the cost and saving estimate entered. These factors can change the result:
- Existing depth: topping up from 100mm to 270mm saves less than insulating an empty loft.
- Property type: detached homes and bungalows often have more exposed roof area.
- Heating fuel: savings can change with gas, electric, oil or heat pump heating costs.
- Installation cost: DIY materials, access problems, boarding and professional labour affect payback.
- Ventilation: poor installation can create damp or condensation risks.
- EPC rating: insulation can support a better EPC rating, but it is only one part of home efficiency.
DIY vs professional installation
DIY can reduce upfront cost if the loft is simple, safe and accessible. Professional installation may be better if the loft has awkward access, damp, electrical concerns, old damaged insulation, or if you need ventilation and boarding considered properly.
Compare full home energy costs
See how insulation savings might affect your wider gas and electricity bill.
Should loft insulation come before a boiler or heat pump?
Insulation can reduce heat loss before you spend money on a heating upgrade. If the loft is poorly insulated, improving it may lower heating demand and make a future heat pump or boiler replacement easier to size.
Compare heating upgrade payback
Estimate boiler or heat pump replacement cost, grants, savings and payback.
Loft insulation savings calculator FAQs
How do I calculate loft insulation payback?
Divide the installation cost by the expected annual saving. For example, £930 ÷ £340 is about 2.7 years.
What insulation depth should I aim for?
Many guidance examples use 270mm as a common target depth for loft insulation, but check what is suitable for your home.
Does loft insulation reduce gas and electricity bills?
It can reduce heating demand, which may lower gas, electricity, oil or other heating costs depending on how your home is heated.
Can I use this for grant-funded insulation?
Yes. Enter the amount you personally pay after any grant or discount as the installation cost.