Smart thermostat schedules and UK heating bills

A thermostat saves money only by shortening the time the heating runs, or by running it less hard. It does not change the price of a unit of gas. The useful question is how many kilowatt-hours of heat you stop using, and what those units cost on the current cap. A schedule is the ordinary way to do that: warmer when people are home and awake, cooler when the house is empty or everyone is asleep.

The gas cap, in pounds

Ofgem’s published GB average for a Direct Debit default tariff, 1 October–31 December 2026, is 7.97p/kWh for gas and a 29.68p/day gas standing charge. The standing charge over 365 days is 29.68p × 365 = £108.33, and it does not fall because a thermostat learned your week. Ofgem’s letter on this cap uses a medium typical domestic consumption value of 9,500 kWh of gas a year (and 2,500 kWh of electricity). The gas units alone at the cap rate would be 9,500 × 7.97p = £757.15, before the standing charge and before any difference between your region and the GB average. Ofgem’s note that the published electricity rates exclude VAT for this winter is about the electricity figures; use the gas table on the same Ofgem page for the 7.97p and 29.68p.

One kilowatt-hour of gas you do not burn is 7.97p on that average. Ten kilowatt-hours not burned is 79.7p. A hundred is £7.97. That is the whole price mechanism. Anything sold as a percentage saving is a claim about how many of those units you avoid.

What a UK study actually measured

The Behavioural Insights Team evaluated the Nest Learning Thermostat in UK homes that already had a programmer, a room thermostat and thermostatic radiator valves. Their summary says the basic thermostat functions saved about 6–7% of heating-system gas (about 4.5–5% of total household gas), and that an optional Seasonal Savings feature was associated with a further reduction among people who opted in. The write-up is from 2017. It is not a 2026 trial, it is not a promise for a house with no controls today, and it is not a result for heat-pump homes. Heat-pump running cost is electricity, at 26.32p or 7.6p, not gas at 7.97p.

If you apply that older 6% figure to Ofgem’s current 9,500 kWh medium gas TDCV, you get 570 kWh, which is 570 × 7.97p = £45.43 of gas units. That multiplication is an illustration so the percentage has a unit attached. It is not a forecast for your house. Homes that already set a sensible schedule may save less. Homes that heat empty rooms all day may save more. The study’s own comparison was against households that already had standard controls.

A schedule that matches how you live

Set the times you are usually in, not a copy of someone else’s chart. A lower target overnight, and a lower target while the house is empty on a work day, are the two changes that remove hours of boiler or heat-pump time. Bring the target back up shortly before you need the rooms warm, so you are not paying to overshoot. If the thermostat can set itself back when phones leave the house, check that it is not dropping the heat while someone is still at home without a phone.

The homepage listing is a tado° radiator starter kit. Each radiator follows its own schedule, so you heat the rooms you use. Give a new schedule a fortnight and compare the heating hours, or the gas units, on the next statement. If you heat with a heat pump on Intelligent Octopus Go, the unit price may be 7.6p/kWh inside 23:30–05:30 and your day rate outside it.

No shelf price was checked, so this page has no payback month. £45 is not “the saving”, and it is not a reason to buy. It is 6% of one official medium gas consumption, priced at the current cap, with the study’s limits written next to it.

Electricity decisions, including EV charging and laundry, stay on the calculator. Heating gas is outside those sliders.

Sources

• Ofgem, unit rates and standing charges
• Ofgem, summary of the October–December 2026 cap (TDCVs)
• Ofgem, price cap 1 October–31 December 2026
• Behavioural Insights Team, Evaluating the Nest Learning Thermostat
• Octopus Energy, Intelligent Octopus Go

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