Heating 12 October 2026

Is It Cheaper to Leave the Heating On All Day? The Answer for Sevenoaks' Big Commuter Houses

No, in almost every house we work on it is not cheaper to leave the heating on all day, and in Sevenoaks that answer is firmer than most places. The town’s big late-Victorian, Edwardian and 1920s houses lose heat quickly through solid brick walls and tall windows, and a large share of them stand empty from early morning until the evening train gets in. Holding a house like that at 20 degrees for twelve hours while nobody is in it is paying to heat the garden.

The catch is that “off all day” is not quite right either, least of all in the big, slow houses Sevenoaks is known for. This guide explains what to set instead and the one situation where a low setting all day is the right call. If your heating is not keeping up at all, call us on 01732 792 454 and we will look at the system rather than the thermostat.

Why Sevenoaks is the wrong place to test the “on all day” idea

Sevenoaks grew up as a railway town. Frequent services to London, 21 miles away at Charing Cross, turned a market town on the Greensand Ridge into a commuter town, and it still has a large commuting population, most of it heading to central London every weekday. That shaped the housing. Sevenoaks District Council’s own appraisal of the Kippington Conservation Area, west of the station, describes large, individually designed houses standing in substantial plots, mostly late-Victorian and Edwardian red brick with a run of 1920s Arts and Crafts houses at the south end of Kippington Road. Granville Road and Eardley Road are much the same.

From a heating engineer’s point of view those houses share three things:

• Solid walls and a lot of glass. There is no cavity to insulate, so the walls pass heat straight out and the bays and sashes do the rest.
• A lot of thermal mass. Thick brick and plaster take a long time to warm up and a long time to cool down.
• An empty day. A commuter household might leave at seven and get back at seven. Twelve hours is a long time to hold a big house at living temperature for nobody.

We are based in Tonbridge, a few miles down the line, and cover Sevenoaks from there. Our Sevenoaks plumbing and heating page covers what we do in the town.

Is it cheaper to leave the heating on all day?

A house loses heat in proportion to the difference between the temperature inside and outside. Hold it at 20 degrees all day in January and the gap is large all day, so the loss is large all day, and the boiler has to replace every bit of it. Let the house drop to 15 degrees while you are out and the loss over the day is smaller. Reheating in the evening costs something, but never more than the heat you would have thrown away keeping an empty house warm.

The argument for leaving it on is that the boiler “works harder” to reheat a cold house. It runs for longer in one go, but a modern condensing boiler is at its most efficient running steadily at a sensible flow temperature, which is exactly what a reheat is. Short bursts to hold a set temperature all day are what make a boiler cycle on and off, the less efficient way to run it.

The one honest caveat is damp. In a cold, solid-walled house with poor ventilation, letting the fabric get very cold for long periods can push moisture into the walls and bring on condensation and mould. That is an argument for a sensible setback temperature, not for heating an empty house to living temperature.

Should I leave my heating on all day on a low setting?

This is the version Sevenoaks households ask most. “Low all day” usually means the room thermostat turned down to 15 or 16 degrees with the programmer on constant.

In a modern, well-insulated house that is a poor idea, because the house barely drops below 16 anyway and you pay the boiler to top it up for nothing. In a big Edwardian house in Kippington it is closer to a draw: the house will fall to 15 on its own within a few hours on a cold day, so holding it there is not far from letting it drift, and it protects the fabric from damp.

What our engineers recommend for that type of house is a proper setback rather than a flat low setting:

1. Heat to living temperature only when people are in. Two periods a day for a commuter household, timed so the house is already warm when you get up and when you get home.
2. Set a setback temperature in between, not off. Around 15 or 16 degrees in a solid-walled house: a floor the house will rarely reach on a mild day, and a safety net on a bitter one.
3. Bring the evening start forward rather than turning the temperature up. A house that takes two hours to warm through needs the heating on at five for a seven o’clock arrival. Turning the thermostat up to 25 does not make it heat faster, it only makes it overshoot later. Our guide to how thermostatic radiator valves work makes the same point at room level.

This is also where smart controls earn their place in a commuter town. A thermostat that knows the household has left, because everyone’s phone has gone to London, and starts the reheat when the first phone is on the train home, does the setback and the early start without anyone remembering to press anything. Our guide to smart heating controls that actually save money sorts the useful from the marketing.

What temperature should I leave the heating on when away in winter?

Going away over Christmas turns the “on or off” question into a “freeze or not” question, and it is when we get the most calls from houses left cold. Our post on frozen pipes in Crowborough covers what happens to a house left with the heating off in a hard frost, and a large Sevenoaks house with loft tanks and long pipe runs through unheated spaces is just as exposed.

• Leave the heating on a frost or holiday setting, never off. Most modern thermostats have a frost protection setting, usually somewhere between 5 and 10 degrees, that only fires the boiler when the house is close to freezing. If yours does not, set the thermostat to around 10 degrees and leave the programmer on constant.
• Check where the thermostat is. A thermostat in a warm hallway can read 12 degrees while the loft and an unheated back extension are below freezing, and in the big period houses that is exactly where the pipes run.
• Know where the stopcock is before you leave. For a long spell away in deep winter, turning the water off and leaving the heating on frost protection is the belt-and-braces option.
• Have the boiler serviced before the cold sets in. A boiler service with us is £95+VAT.

When the thermostat is not the problem

Sometimes a Sevenoaks household has the heating on all day because it is the only way the house ever feels warm. If it runs from six in the morning and the living room is still cool at ten, the answer is not a different schedule. It is a system that cannot deliver enough heat to a house that loses it quickly.

What we find on those visits is familiar: radiators sized decades ago that cannot keep up at condensing flow temperatures, long unbalanced pipe runs under suspended floors, sludge in the ground-floor radiators, and a single hall thermostat trying to run three floors. We wrote about the same pattern in heating a Victorian house in Tunbridge Wells, and it applies just as well on this side of the Greensand Ridge.

Our engineers look at heat loss, water quality, balancing and controls before anyone talks about a bigger boiler. Sometimes the right answer is a new boiler sized properly for the house, and we will say so with a free fixed written quote. Diagnosis is charged at £95+VAT for the first hour, then £47.50+VAT per 30 minutes after that, and anything on the gas side of the boiler is carried out by a Gas Safe registered engineer.

If you would like us to look at how your heating is set up, or it is simply not keeping up this winter, call Plumbing Angels on 01732 792 454. We are Gas Safe registered and cover Sevenoaks from our base in Tonbridge.