Rental tenants are usually told they cannot change the heating system. That is partly true and partly a habit landlords benefit from. The user-level controls, boiler flow temperature, radiator valves, and thermostat schedule, are yours to adjust and can move a heating bill by more than a smart thermostat upgrade ever will. This guide covers the specific numbers to change, why they matter, and where the strategy needs landlord involvement.
Everything below assumes a gas combi boiler with radiators, the most common UK and European rental setup. Storage-heater flats and heat-pump flats need different guidance.
The boiler flow temperature, the single biggest lever
Boiler flow temperature is the temperature of the water pumped into the radiators. Most combi boilers ship set at 75 to 80°C, which was correct in older single-glazed housing and is wrong for most modern flats. Reducing to 60°C typically:
- Cuts gas consumption 8 to 12 percent across a heating season.
- Lengthens the burn cycle, which is quieter and easier on the boiler.
- Reduces the water-return-temperature enough that condensing boilers can actually condense, which is the mechanism they were designed around.
To change it: locate the “central heating” or radiator-icon dial on the boiler front (not the “hot water” dial). Turn to the middle of its range, roughly 60°C on most models. That is it. The radiators will feel less hot to the touch and heat the room over a longer, gentler cycle.
The dial that does not do what most tenants think it does
The “hot water” temperature dial on a combi boiler controls the tap water, not the radiators. Set it to 55°C for showers and washing up. Any higher wastes gas and scalds; any lower feels wrong at the mixer tap.
Radiator valves (TRVs), the boring detail that halves cold-room bills
Every radiator has a valve at one end with numbers 1 to 5 (or *, 1 to 5). These are Thermostatic Radiator Valves. The number is not “how hot” the radiator gets, it is “what room temperature the valve targets before shutting the radiator off”. Rough mapping:
- Number 1: ~12°C. Keep pipes from freezing, nothing more.
- Number 2: ~16°C. Spare rooms, hallway.
- Number 3: ~20°C. Living rooms, kitchen (default).
- Number 4: ~24°C. Warmer than most people want to sit in.
- Number 5: ~28°C. Sauna. Do not.
The practical move: turn spare bedrooms, hallways, and any room you do not sit in for hours to Number 2. Leave living rooms and bedrooms you use to Number 3. The kitchen usually needs no TRV attention because cooking heat handles the rest.
Related: Winter Heating Savings Tips covers the behaviour and habit side once the settings are right.
The main thermostat
Most rental flats have one thermostat in a hallway or living room. Two behaviours dominate the bill:
- Set it once, leave it. The dial-up-then-dial-down habit does not warm the room faster; it just overshoots and wastes gas. Pick a single winter setpoint, 19 to 20°C, and leave it.
- Use the schedule. If the thermostat has a schedule (most built after 2015 do), set it to run 30 minutes before you wake, 30 minutes before you return, and off overnight and mid-day. A schedule saves roughly 8 to 15 percent versus leaving it constant at 20°C.
Smart thermostats add app control but the savings mainly come from schedules that a basic timer already handles. Landlord will not approve a smart thermostat swap? The scheduled bill is still available on the box you have.
What actually needs the landlord
These do need permission or a maintenance visit:
- Boiler service if it has been more than 12 months.
- Radiator bleeding if valves stopped working or radiators are cold at the top.
- Insulation of any pipe or tank, which can save further gas but changes fabric.
- Any TRV that is stuck at a number and cannot be turned; replacement is a £15 to £25 fix but is a maintenance job.
These are all reasonable requests. Landlords benefit from lower bills passing through to lower complaints, and gas safety certificates are their obligation anyway.
Quick reference: the settings to change today
| Setting | Change to |
|---|---|
| Boiler flow temperature | 60°C in winter, 55°C in shoulder seasons |
| Boiler hot water temperature | 55°C |
| Living room TRV | Number 3 (~20°C) |
| Bedroom TRV (in use) | Number 3, or Number 2 overnight |
| Spare room TRV | Number 2 (~16°C) |
| Hallway TRV | Number 1 or 2 |
| Main thermostat setpoint | 19 to 20°C, on a schedule |
Where these numbers do not apply
Two flats where the guidance shifts:
- Heat-pump flats. Flow temperatures above 50°C break heat-pump efficiency; the whole system runs colder and longer. Do not raise flow temperature on a heat pump.
- Old solid-fuel or storage-heater flats. Different physics entirely. The main lever there is the input-time window, not a valve.
Small, correct settings changes on the existing boiler quietly beat almost every smart-home upgrade a renter can bolt on. Change the boiler flow, set the TRVs, use the schedule. That is the entire strategy.
The one-week measurement experiment
If you doubt any of the numbers above, run a one-week comparison. Week one: leave the boiler flow at whatever the previous tenant set. Photograph the gas meter reading on day one and day seven at the same time. Week two: reduce flow to 60°C and adjust TRVs as described. Photograph the meter again on day one and day seven of the new settings. The difference in daily gas consumption is usually visible after a single week in winter, and unmistakable across a fortnight. This is the only convincing way to change a partner’s or flatmate’s mind about the settings, and it produces the number for the next tenancy conversation.
What breaks in the second half of the winter
Two failure modes emerge around January in flats using these settings. One: a radiator that used to warm the room now feels lukewarm. This is usually air in the system (a landlord-callable bleed job) or a stuck TRV. Two: the flat feels colder than it did last year at the same setpoint. This is usually seals degrading somewhere; check draughts around door and windows before assuming the boiler is failing. Both are solvable and neither invalidates the settings.
Sources and further reading
Frequently asked questions
For radiators in an average-sized flat, 60°C is a good starting point in mid-winter and 55°C works in shoulder seasons. Below 50°C the room will not warm up on the coldest days. Above 70°C burns more gas per degree of room heat.
For flow temperature, TRV numbers, and thermostat schedules: no. These are user controls, not maintenance work, and the lease treats them the same way it treats the light switches. If in doubt, an email note is a courtesy.
A UK Energy Saving Trust field study suggested combi-boiler households cutting flow from 80°C to 60°C save around 8 to 12 percent of gas consumption over a heating season, roughly £70 to £120 on a typical UK bill at 2026 unit rates.
Rough guide: TRV 1 corresponds to about 12°C, 2 to 16°C, 3 to 20°C, 4 to 24°C, 5 to 28°C. Aim TRVs at rooms you actually use and turn spare rooms to 2 or lower.
