The one principle that orders everything
Fabric first. Roughly a quarter of a typical home’s heat escapes through the roof, a third through the walls, and a steady trickle through gaps, floors and windows. Every kilowatt-hour of heat your house doesn’t lose is one you never pay to generate — at any tariff, under any government, forever. So the sequence is always: reduce demand first (insulation, draught-proofing), upgrade the heat source second (heat pump vs boiler), generate your own last (solar, battery). Doing it backwards — panels on an uninsulated roof — means buying expensive kit to feed a leaky building.
The other framing worth adopting early: these are investments with calculable paybacks, and the paybacks vary from months (draught-proofing) to decades (some glazing). This section is largely about knowing which is which before spending.
Step one: measure before you spend
Your home almost certainly has an Energy Performance Certificate already — every home sold or let in the last decade has one, and they’re all public on the gov.uk register. It grades the home A–G, lists recommended improvements with cost and saving estimates, and costs nothing to look up. It’s an imperfect model, but it’s the map you start from — the EPC guide explains how the score works, why it affects bills, mortgages and rentability, and the cheapest routes up a band.
What makes sense at different budgets
| Budget | Best value moves |
|---|---|
| Under £250 | Draught-proofing strips, letterbox brushes, chimney balloon, radiator reflectors, hot water cylinder jacket — £50–£250 DIY for the lot. Paybacks in months; nothing else in this section beats them. |
| £250 – £1,000 | Loft insulation topped up to 270mm+ (the single best £/saving ratio in home energy), thermostatic radiator valves, a proper heating-control setup. And one free move that belongs here: a smart meter plus a smart tariff. |
| £1,000 – £10,000 | Cavity wall insulation if you have unfilled cavities (~£1,000–£3,000, pays back in a few years); floor insulation; quality secondary glazing. See the insulation guide for the full pecking order by payback. |
| £10,000+ | The heat source and generation tier: an air-source heat pump (with the £7,500 grant it often costs no more than a boiler swap) and/or solar panels with or without a battery. These are the heat pump guide’s and solar guide’s territory — and where doing the sums first matters most. |
What makes sense for different homes and situations
- Renters: You can’t insulate someone else’s wall, but draught-proofing, radiator reflectors and heating controls travel with you or cost little. Check the property’s EPC — landlords must meet minimum standards to let legally, and the register is public.
- Older homes (pre-1930, solid walls): No cavity to fill, so wall insulation is expensive (£8,000–£25,000) and the cheap wins — loft, draughts, floors — matter proportionally more. Heat pumps can work in period homes, but radiator sizing and fabric come first.
- Post-1990 homes: Probably already at EPC C-ish with filled cavities and decent loft insulation. The marginal wins are controls, topping up the loft, and then jumping straight to the generation tier.
- Off-gas homes (oil, LPG, electric heating): The heat pump maths improves dramatically — displacing oil or direct electric heating rather than cheap mains gas makes payback several years faster. If this is you, read the heat pump guide first, not last.
- High electricity users / EV owners: Solar and batteries pay back fastest when you can use what you generate — an EV, a heat pump or daytime working shifts the economics meaningfully. An EV owner’s first move is a dedicated overnight tariff (~2p per mile); then run your actual solar numbers in the ROI simulator before believing any installer’s quote.
Grants worth knowing about
The Boiler Upgrade Scheme pays £7,500 toward a heat pump in England and Wales. ECO4 (ending December 2026) and the Warm Homes: Local Grant fund insulation and heating upgrades for lower-income households and homes with poor EPC ratings, and Scotland, Wales and Northern Ireland run their own schemes. The grants and schemes guide collects the lot — who qualifies, what each is worth, and where to check. Schemes change and budgets run out, so confirm before assuming a price — but never let a grant reverse the fabric-first order: subsidised kit in a leaky house is still heating the street.
The £50 draught-proofing weekend routinely outperforms the £15,000 glazing project on every financial measure. In home energy, spending more is easy; spending in the right order is the entire game.
The guides in this section
- Insulation and draught-proofing — the cheapest heat you’ll ever buy: the full pecking order of insulation measures by payback time, typical UK costs, and the £50 fixes that beat the £15,000 ones.
- Heating controls — the settings you already own: thermostats, TRVs, timers and the boiler flow-temperature trick worth 10–20% of the heating bill for free.
- Heat pumps vs gas boilers — the honest comparison: how heat pumps actually work, real installation and running costs with the £7,500 grant, and which homes they suit today.
- EPC ratings — what the A–G bands actually measure, why they matter for bills, rentals and resale, and the cheapest routes to a better band.
- Solar, batteries and smart tariffs — where solar savings really come from, what a battery adds, and how export payments and time-of-use tariffs change the sums.
- Smart tariffs and EV charging — the zero-hardware savings: time-of-use tariffs, ~2p-per-mile EV motoring, and why the smart meter is the free upgrade that unlocks the rest.
- Case study — taking a 1920s house from EPC F to C — the whole sequence above applied to one real 1920s house: every project, what it cost, what worked, and what I’d do differently.
- UK energy grants and schemes — what help you can get: every live scheme across the four nations in one place, from the £7,500 heat pump grant to the £150 Warm Home Discount.
Related guides & tools
- Home Energy Test — 20 questions to find your knowledge gaps before you spend anything
- Solar & Battery ROI Simulator — run your own roof, usage and tariff numbers with honest uncertainty ranges
- Emergency funds and where to keep cash — big efficiency projects shouldn’t drain the cash buffer that protects everything else
Last reviewed: August 2026.