When Should You Put the Heating On? A Gas Cost Guide

The short answer: put the heating on when the home feels cold

Putting the heating on is not a contest to reach a particular date. For a home with a gas boiler, turn it on when the rooms you use are becoming uncomfortably cold, then let the thermostat and timer prevent unnecessary running. Energy Saving Trust says this is especially important if an older person or someone with a medical condition lives in the home.

The NHS says to heat your home to a temperature that is comfortable for you and, if possible, to at least 18°C in rooms you use regularly, such as the living room and bedroom. Health needs come before an arbitrary target for delaying the heating.

Start with a sensible schedule, observe how quickly the home warms and measure the gas used. That gives you a more useful answer than copying somebody else’s switch-on date or treating the boiler’s maximum output as its constant consumption.

There is no official “heating-on date”

Weather, insulation, exposure and the people in the home matter more than the date. Energy Saving Trust says people often start thinking about heating from September and that the regular heating season for most homes runs from roughly October to March or April. Its practical answer is to switch the heating on when you start to feel cold.

Do not wait for a particular outdoor temperature if occupied rooms are already uncomfortable. A well-insulated mid-terrace and a draughty detached home can feel very different on the same day. Older people, babies and people with some health conditions can be more vulnerable to cold.

A simple room thermometer can help when the wall thermostat is in a hallway that does not represent the living room or bedroom. Treat 18°C as health guidance, not a universal comfort ceiling: household needs and room temperatures vary.

Set the thermostat and timer to do different jobs

The timer decides when heating is available. The room thermostat decides whether the boiler needs to fire during those periods. Energy Saving Trust gives a general thermostat range of 18–21°C and suggests programming heat to begin about half an hour before waking and stop about half an hour before bed.

Those half-hour timings are a starting point, not a rule. Homes warm and cool at different speeds. Move the start time in small steps until occupied rooms are comfortable when needed. If everyone is out for a regular block of time, schedule the boiler off or cooler during that absence rather than heating an empty home.

With a gas boiler, leaving the heating on all day normally uses more energy than running it when needed. Do not copy this advice to a heat pump: Energy Saving Trust says heat pumps generally work best with steadier operation. Our central heating controls guide explains the separate jobs of timers, thermostats and radiator valves.

Work out what switching the heating on costs

There is no reliable universal hourly figure because boilers modulate and cycle. The cost depends on heat loss, weather, settings, hot-water use, boiler performance and tariff. Measure the change in gas kWh instead of multiplying the boiler’s maximum output by every hour it is switched on.

Use extra gas kWh × gas unit rate in pounds = extra usage cost. Suppose total household gas use rises by 10 kWh a day after the heating starts. At Ofgem’s average Great Britain Direct Debit cap rate of 7.97p/kWh for 1 October to 31 December 2026, the calculation is 10 × £0.0797 = £0.797 a day, or £23.91 across 30 days.

This is an illustration, not a prediction. Use the unit rate on your tariff because rates vary by region, payment method and contract. The daily standing charge is not added to the difference: you pay it while connected whether or not the boiler runs. The boiler running-cost guide explains why measured consumption is more useful than the number printed on the boiler.

Illustration using Ofgem’s Great Britain average Direct Debit gas rate for 1 October–31 December 2026. It excludes the standing charge and uses rounded display figures; use your own tariff.

Run a simple seven-day gas check

Take a dated meter reading before a settled week of heating use and another seven days later. Use the same meter, record only the whole digits and note unusual hot-water or cooking use. Enter the readings, dates and tariff into the gas bill calculator to estimate the period cost.

Compare weeks cautiously. Colder weather can raise demand even when settings do not change. Guests, more baths or showers, and being home for longer can also change gas use. A useful test changes one setting at a time—for example, moving the morning start 15 minutes later—then compares broadly similar weather and routines.

If you want an hourly snapshot, read the meter before and after one normal heating period, but remember that this captures all household gas use during the test. Keep the original readings so you can distinguish the measured result from an estimate.

• Before: photograph or record the meter reading, date and time.
• During: keep the schedule stable and note unusual gas use.
• After: take the second reading at roughly the same time of day.
• Calculate: apply the exact gas rate on your tariff, not a national average.
• Interpret: consider weather and occupancy before changing a setting.

Get the system ready before the first cold spell

Run the heating briefly before you urgently need it. Confirm that the thermostat calls for heat, radiators warm up and no warning code appears. Keep furniture and curtains from blocking radiators. If a radiator is cold at the top, follow the manufacturer’s instructions or use a competent professional rather than improvising.

Check when the boiler was last serviced. HSE strongly advises homeowners to have gas appliances regularly maintained and serviced at least annually by a Gas Safe registered engineer. Do not remove the boiler casing or attempt gas work. If you suspect an appliance is unsafe, switch it off and arrange a qualified check. Our boiler service guide explains what to book and check.

Efficiency settings are separate from room temperature. Some combi-boiler households can reduce radiator flow temperature, but systems with a hot-water cylinder need different care. Use our boiler flow-temperature guide rather than changing unfamiliar controls.

Keep comfort and affordability in the same plan

Reducing waste should not mean leaving vulnerable people in a cold home. Heat the rooms you use, close doors between warmer and cooler areas where appropriate, and use radiator valves to avoid overheating little-used spaces. Never block fixed ventilation.

If cost is the reason you are delaying necessary heat, contact the supplier early. Ask about an affordable payment plan and available support. Our help paying a gas bill guide sets out the conversation and the separate Great Britain and Northern Ireland routes.

Ofgem’s price-cap figures in the worked example apply to England, Scotland and Wales. Northern Ireland has a separate gas market and regulated-tariff system. In every UK nation, use the unit rate and standing charge shown on your own tariff rather than importing an average figure.