Do smart thermostats actually save money?
Usually, yes, though rarely by the dramatic amount the box implies, and nobody credible will give you a single guaranteed number. Energy Saving Trust estimates that installing heating controls could save around £100 a year in Great Britain, and £110 in Northern Ireland. Turning your thermostat down by one degree, from 22°C to 21°C, is put at around £120 a year in GB and £80 in NI.
Notice what those figures are not. They are for heating controls and thermostat settings generally, not for a smart thermostat specifically. Energy Saving Trust deliberately does not publish a single smart thermostat savings figure, because, in its words, whether smart heating controls save you money “will depend on how you currently control your heating”. That is the honest answer, and it is more useful than a made-up range.
Smart thermostat savings come from small, boring adjustments repeated every day. Turning the heating down a degree, not warming an empty house, not overshooting a room that was already comfortable. None of that needs to be clever. It just needs to actually happen, which is exactly where a dial-and-hope thermostat usually fails.
What smart thermostat savings actually depend on
The honest variable is what you are replacing. If you are coming from a manual dial nobody has touched in years, or heating that still runs on a schedule built around a job you left in 2019, a smart thermostat is closing a big gap and the saving can be meaningful.
If you already have a decent programmable timer, set sensibly, and you actually stick to it, a smart thermostat is closing a much smaller gap. The main gain then is convenience rather than a dramatic cut to the bill. That is not a reason to avoid one, but it is a reason to be realistic about the payback.
Household size and how much you are actually home during the day change the numbers too. A house empty from 8am to 6pm, heated the whole time out of habit, has far more slack to cut than a home with someone in it all day who already turns the dial down without being asked.
Worth saying plainly: any figure you see quoted for smart thermostat savings, here or anywhere else, is an estimate built on a typical household that may look nothing like yours. Treat them as a rough guide to the size of the opportunity, not a promise.
What actually drives the saving
The thermostat itself does not save you anything. It is a tool, not a magic trick. The saving comes from the habits it makes easier: turning heating off automatically when nobody is home, scheduling a lower temperature overnight, and getting an honest read on what a room actually costs to heat.
Smart thermostat savings tend to shrink fast if you just leave the default settings running and never look at the app again. The households that get the most out of one tend to be the ones who check in occasionally and actually adjust the schedule as the weather changes.
This is also why the single biggest lever is the cheapest one. Energy Saving Trust’s £120 figure for dropping one degree needs no hardware at all. A smart thermostat mostly helps by making that kind of change stick without anyone having to remember it.
Do smart radiator valves add much?
They can, in the right house. Smart radiator valves let you heat only the rooms you are actually using, rather than the whole house to one temperature. In a larger home with rooms that sit empty most of the day, that is where room-by-room control earns its place.
In a small, well insulated flat where every room gets used, the extra cost of valves is harder to justify. Energy Saving Trust does not publish a separate savings figure for valves either, for the same reason it avoids one for smart thermostats: it depends entirely on what you are replacing and how you live in the space.
Five things to check before you buy
Key takeaways
- Check it is compatible with your existing boiler or heating system before ordering, not after.
- Factor in installation cost, some models are simple DIY, others need an engineer.
- Look for room-by-room control (via smart radiator valves) if only some rooms need help.
- Set a genuinely lower overnight and away-from-home schedule, the thermostat cannot guess that for you.
- Review the schedule every few weeks, smart thermostat savings fade if the settings just sit there.
Pair sensible heating habits with basic draught proofing and the two effects stack, since less heat leaking out means a thermostat has less to fight in the first place.
The bigger lever most people skip
Smart thermostat savings only trim how you use heating you already have. A thermostat will not fix a boiler that is quietly running inefficiently, or a home losing heat through gaps nobody has noticed. A quick boiler service and a sensible view of when to turn the heating on in the first place both matter as much as the gadget itself.
None of this replaces checking you are actually on a competitive energy rate to begin with. A smart thermostat cuts how much you use. The tariff decides what each unit costs you, and no amount of clever scheduling fixes a bad rate. Roo would say sort both, not just the gadget.
Frequently asked questions about smart thermostat savings
- How much do smart thermostat savings actually add up to in a year?
- There is no single reliable figure. Energy Saving Trust estimates around £100 a year in GB for installing heating controls generally, and around £120 a year for turning your thermostat down one degree, but it does not publish a smart-thermostat-specific number because the saving depends on how you control your heating now.
- Do I need a new boiler to use a smart thermostat?
- No, most smart thermostats are designed to work with existing boilers. It is worth checking compatibility with your specific model before buying, since a small number of systems need an adapter.
- Can I install a smart thermostat myself?
- Some models are designed for DIY installation, while others involve wiring that is safer left to a qualified engineer. Check the specific model’s requirements before you commit.
- Do smart thermostats work with all types of heating?
- Most work well with standard gas central heating. Compatibility with heat pumps, electric storage heaters or underfloor heating varies by brand, so it is worth checking before buying.
- Is a smart thermostat worth it in a small, well insulated flat?
- The saving is likely to be smaller than in a larger, draughtier home, since there is less waste to cut. It may still be worth it for the convenience alone.
Sources: Energy Saving Trust guidance on thermostats and heating controls, checked September 2026.
