Retrofit Tools & Calculators
Twenty free calculators and planners for UK homes — every number computed in your browser, no signup, no data collected.
Solar Panel ROI Calculator
Payback, 25-year profit and CO₂ for your roof, region and orientation.
Open tool ›Heat Pump vs Gas Boiler Calculator
Honest running-cost comparison at your tariffs — including when the heat pump loses.
Open tool ›Home Energy Audit Tool
15 questions, an estimated EPC band, and your top 3 retrofit recommendations.
Open tool ›Insulation Savings Calculator
Loft, cavity, solid wall or floor — savings, payback and 10-year net.
Open tool ›Home Carbon Footprint Calculator
Gas, electricity, car, flights and diet — your total vs the UK average.
Open tool ›Double Glazing ROI Calculator
The honest payback math, plus comfort, noise and condensation benefits.
Open tool ›EV Home Charger Cost Calculator
Petrol vs electric pence-per-mile, charger payback, tariff advice.
Open tool ›Smart Thermostat Savings Estimator
What zoned control and geofencing really save on your heating bill.
Open tool ›Grant & Subsidy Finder
BUS, ECO4, GBIS, Home Energy Scotland, 0% VAT — what you're eligible for.
Open tool ›Green Mortgage Checker
Monthly payment maths for green discounts, and who actually qualifies.
Open tool ›Cavity Wall Suitability Checker
Safety-critical quiz: is your wall safe to fill, or does it need a survey?
Open tool ›Draught-Proofing Savings Calculator
Doors, windows, chimney, floorboards — DIY vs professional payback.
Open tool ›Solar Battery Payback Calculator
Blunt maths on whether a home battery ever pays for itself.
Open tool ›Heat Pump Readiness Quiz
Is your home ready? Scored quiz with a prioritised upgrade list.
Open tool ›Hot Water Cylinder Jacket Calculator
The cheapest win on this site — £35, five months payback.
Open tool ›LED Lighting Savings Calculator
Bulb-by-bulb payback, lumens buying guide, dimmer compatibility.
Open tool ›Standby Power Cost Calculator
What your idle devices cost per year, ranked by biggest waster.
Open tool ›Green Tariff Comparison Calculator
Compare green tariffs by true annual cost — example rates, live-quote method.
Open tool ›Whole-House Retrofit Planner
Your home sequenced into quick wins → fabric → systems, inside your budget.
Open tool ›EPC Improvement Estimator
SAP point gains per measure — project your band, rank by points-per-pound.
Open tool ›How to use these tools
Start with the Home Energy Audit if you don't know where your home stands — fifteen questions, an estimated EPC band, and your top three recommendations. Then work the quick wins: the LED calculator, standby checker, draught-proofing and cylinder jacket calculators all pay back in under two years, most in months.
When you're ready to plan properly, the Whole-House Retrofit Planner sequences everything into three phases — quick wins, fabric, then systems — inside your budget. The EPC Improvement Estimator shows what each measure does to your rating. And before you spend serious money, check the Grant & Subsidy Finder: thousands of pounds of support go unclaimed every year.
One house rule runs through every tool here: the maths is honest, including when it says a measure doesn't pay. Heat pumps can cost more to run than gas at current price ratios. Batteries rarely pay for themselves. Double glazing pays back in decades. We'd rather you know that before the quote than after the invoice.