Complete Setup · Updated September 2026
The Energy Efficiency Bundle
Cut your bills using the boiler, radiators and hot water system you already own. Six steps, ordered by how much you save per pound spent — and the first two are free.
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⏱️ The 30-second version
- 🔥 Turn your boiler's flow temperature down — free, takes two minutes, most people have it set far too high
- 📊 Check you're on the right tariff — free, and often the single biggest saving on this page
- 🚿 Insulate your hot water cylinder — ~£25, one of the best paybacks in any home
- 🚪 Draught-proof — cheap, unglamorous, genuinely works
- 🌡️ Smart controls only after the above — they optimise a system, they don't fix a badly set one
- 🏠 Check ECO4 eligibility before 31 December — insulation may be free
Why this order
Most energy-saving advice starts with buying something. But in a typical UK home, the biggest wins are usually settings that are wrong rather than kit that's missing — a boiler running hotter than it needs to, a hot water cylinder losing heat all day, a tariff that stopped being competitive two years ago.
So this bundle runs free-first. If you stop after step two you'll have spent nothing and quite possibly saved more than someone who spent £300. Everything here works with the heating system you already have — no new boiler, no heat pump, no solar. If you're weighing up a bigger upgrade instead, our heat pumps guide covers the £7,500 grant.
Turn down your boiler's flow temperature
This is not your thermostat. It's a separate dial or menu setting on the boiler itself, controlling how hot the water is that goes out to your radiators. Most UK combi boilers leave the factory set around 70–80°C, which is hotter than the boiler needs — and, counterintuitively, hotter than it wants.
A condensing boiler only reaches its advertised efficiency when the water returning to it is cool enough for the flue gases to condense. Run the flow too hot and that never happens, so you're paying for an efficiency you never receive. Dropping the flow temperature to around 60°C typically improves efficiency by several percent on your entire gas bill, for free, in about two minutes.
How to do it: find the radiator symbol (🌡️ or a wavy-line radiator icon) on your boiler's control panel — not the tap symbol, which is hot water. Turn it to around 60°C. Leave the hot water setting alone. Your home will still reach the same temperature; radiators will simply run cooler for longer, which is how condensing boilers are designed to work.
⚠️ Two exceptions. This applies to combi and system boilers, not heat pumps (which have their own optimisation). And if your home struggles to get warm on the coldest days after the change, nudge it back up in 5°C steps — comfort first.
Check your tariff and your settings
Four things worth ten minutes of your time, all free:
- Your tariff. If you've never switched, or you rolled onto a standard variable tariff, compare what's available. If you have an EV, a battery or storage heaters, a time-of-use tariff can cut costs substantially — see our Octopus tariff comparison.
- Your thermostat. Turning it down by 1°C is one of the most reliable savings available in any home. 18–20°C is the usual comfortable range.
- Your hot water timer. If you have a cylinder heating water 24/7, set it to heat before you actually need it instead. If you have a combi, this doesn't apply.
- Your radiator valves. Turn thermostatic valves down in rooms you don't use. Bleed any radiator that's cold at the top — trapped air means you're heating water that never reaches the room.
Insulate what's already leaking heat
Boring, cheap, and among the best paybacks in any home. If you have an older hot water cylinder with a thin jacket or none at all, this is genuinely the best £25 on this page — an uninsulated cylinder loses heat continuously, all year, whether you use the water or not.
Stop the draughts
Draught-proofing is the least glamorous item here and one of the most reliable. It's also the same kit that helps in summer — sealing a room works in both directions, which is why it appears in our heatwave bundle too.
Target, in order: letterbox and keyhole, gaps under external doors, window frames, unused chimneys, and gaps around loft hatches and floorboards.
See where the money actually goes
You can't fix what you can't see. Most households are surprised by which appliances dominate their bill, and almost everyone has at least one thing drawing power around the clock for no reason.
Add smart controls — last, not first
Smart heating controls are genuinely useful, but they optimise a system rather than fix a badly configured one. Fit them after steps 1–4 and you're automating an efficient setup. Fit them first and you're just controlling an inefficient one more precisely.
The biggest real-world win is room-by-room control: heating the rooms you're in rather than the whole house to the same temperature.
⚠️ Radiator thermostats give room-by-room control but don't fire the boiler themselves, so they work alongside your existing thermostat rather than replacing it. Scheduling and remote control are free; geofencing and open-window detection need a subscription. More options in our smart home energy guide.
Before you spend anything: check if you qualify for free insulation
The ECO4 scheme can cover loft insulation, cavity wall insulation and other measures at no cost for eligible households — typically those on certain benefits, or in some cases on low incomes in poorly insulated homes. ECO4 closes on 31 December 2026, with the Warm Homes Plan taking over from January 2027.
Proper insulation saves far more than everything else on this page combined. If there's any chance you're eligible, check before buying draught strips — it takes two minutes and the measures are free if you qualify. See our full insulation guide for costs if you don't.
Check ECO4 Eligibility →Three builds, three budgets
The free build
£0
- Boiler flow temperature
- Thermostat and timer
- Bleed and balance radiators
- Tariff check
Do this first, whatever else you decide.
The £75 build
£60–£90
- Everything free above
- Cylinder jacket
- Draught-proofing kit
- Pipe lagging
Best value on this page. Recommended for most homes.
The full build
£250–£300
- Everything above
- Smart radiator controls
- Energy monitoring
- Chimney draught excluder
Worth it if you're in the house all day.
Best time to do this: September and October, before the heating goes on. Everything on this page is cheaper and more available outside winter, and you get the benefit across the whole heating season rather than half of it. Doing it in January means paying peak prices for half the payback.
Done all this and still paying too much?
Insulation and heating upgrades are where the big savings live — and grants may cover a substantial part of the cost. Get free quotes from vetted local installers.
Get Free Quotes →See also: insulation guide · smart home energy · heat pumps and the £7,500 grant · the heatwave survival bundle
Last updated September 2026. Electricity costs based on the October 2026 Ofgem price cap of 26.32p/kWh. Savings vary considerably by property type, existing insulation, occupancy and heating patterns — figures here are indicative rather than guaranteed. General guidance only, not a substitute for advice from a qualified heating engineer. Always check current ECO4 eligibility criteria directly, as scheme rules change.