Heating Controls Guide: From Basic Timers to Smart Thermostats

Why Heating Controls Matter

Heating your home when it is empty, at a uniform temperature throughout regardless of which rooms are occupied, or at a constant temperature when a lower setback during sleeping hours would suffice — all of these represent wasted energy and wasted money. A boiler with no controls beyond an on/off switch is a crude instrument. Layering heating controls progressively onto any system brings progressively greater efficiency, comfort, and cost savings.

The Carbon Trust estimates that fitting and properly using heating controls in a standard UK home can save £150–£300 per year, depending on the level of control installed and the property's previous control setup.

Level 1: Basic Controls

Timeswitch or Programmer

The most basic heating control is a timeswitch — a mechanical or digital clock that turns the heating on and off at preset times. A basic programmer allows separate on/off times for heating and hot water (for systems with a hot water cylinder) and typically allows different programmes for weekdays and weekends.

A programmer alone is not adequate control — it turns the boiler on and off but does not regulate the temperature to which the house heats. Without a room thermostat, the boiler will cycle on and off based solely on the time schedule, regardless of whether the house is already at the desired temperature or is much colder than expected.

Room Thermostat

A room thermostat measures the air temperature in the room where it is installed and signals the boiler to fire when the temperature falls below the setpoint, and to stop firing when the setpoint is reached. A timeswitch combined with a room thermostat provides the basic control package that delivers meaningful efficiency — the heating runs only when the house is scheduled to be occupied and only until the target temperature is reached.

The correct position for a room thermostat is in the main living area, at head height, away from direct sunlight, draughts, or heat sources (radiators, lamps) that would give a false temperature reading. A thermostat poorly positioned — next to a radiator or in a hallway — will control heating inefficiently.

Level 2: Intermediate Controls

Thermostatic Radiator Valves (TRVs)

A thermostatic radiator valve is fitted on the inlet side of each radiator and regulates the flow of hot water into that radiator based on the air temperature in the room. The TRV contains a wax or liquid-filled capsule that expands as the room warms, gradually closing the valve and reducing radiator heat output. As the room cools, the capsule contracts and the valve opens again.

TRVs allow each room to be maintained at a different temperature — a bedroom set to 16°C while the living room is at 21°C, for example — without the need for a separate thermostat and boiler signal for each room. They work in conjunction with the main room thermostat, which controls when the boiler fires; the TRVs control how much heat each radiator contributes to each room.

TRVs should not be fitted on the radiator in the room where the main room thermostat is located — that radiator must be able to run freely to give the thermostat accurate feedback about the whole system.

Zone Valves for Separate Zones

A larger London house can be divided into heating zones — typically downstairs and upstairs — each with its own programmer, room thermostat, and motorised zone valve. This allows the ground floor to be heated in the morning without heating the bedroom floor until evening. Zone separation is a more advanced installation requiring additional pipework, zone valves, and wiring, but the energy saving for a large house is significant.

Level 3: Smart Thermostats

Smart thermostats bring wireless control, app management, and algorithmic optimisation to the basic room thermostat function. The UK market has several well-established options with different feature sets:

Nest Learning Thermostat (Google)

The Nest Learning Thermostat observes your heating adjustments over one to two weeks and builds an automatic schedule based on your patterns — when you wake up, when you leave, when you return, when you go to bed. It uses the property's occupancy detection (via the thermostat's built-in sensors and the Nest app on your phone's location data) to switch to an eco-setback temperature when the home is empty. It also uses Nest's time-to-temperature algorithm — learning how long the property takes to reach the setpoint from different starting temperatures — to start heating at the right time to reach temperature by a target time, rather than running from a fixed start time regardless of conditions.

Installation requires a C-wire (common wire) connection from the thermostat backplate to the boiler, or a Nest Heat Link module wired at the boiler. Installation must be carried out by a Gas Safe registered engineer if the wiring involves any connection to the boiler's gas or electrical controls — and it typically does for a combi boiler installation.

Hive Active Heating (Centrica/British Gas)

Hive Active Heating is the most widely installed smart thermostat in the UK. It is simpler than Nest — it does not learn automatically; schedules are set manually via the app. However, it is compatible with the widest range of boiler types and models, offers reliable remote control from the app, and has strong engineer familiarity given its installation through British Gas's engineer network. The Hive multizone system extends to individual room control via wireless Hive TRVs on each radiator.

tado (Weather Compensation)

tado's distinguishing feature is weather compensation — the thermostat uses real-time local weather data to adjust the boiler's target flow temperature, reducing energy consumption when external temperatures are milder than the design condition. On a mild London autumn day when the heating is running, tado will run the boiler at a lower flow temperature than on a cold January day, improving efficiency by keeping the boiler in condensing mode for longer. Tado also offers geofencing — switching to eco mode when all household members have left and resuming heating automatically as they approach home.

Drayton Wiser (Multi-Zone at Lower Cost)

The Drayton Wiser system provides multi-zone smart heating control at a more accessible price point than competing systems. Wireless smart TRVs fitted on each radiator communicate with a central hub connected to the boiler, allowing individual room scheduling and temperature control without the cost of a fully zoned pipework system. For a London Victorian house where multi-zone pipework would require significant disruption, Wiser TRVs offer a wireless alternative that approximates multi-zone control. The app interface is functional if less refined than Nest or tado.

Boiler Plus Requirements (Since 2018)

The Building Regulations Part L update known as Boiler Plus, which came into force in April 2018, requires that any new combi boiler installation in England must include at least one of the following efficiency measures:

• Flue gas heat recovery device
• Weather compensation
• Load compensation
• Smart thermostat with automation and optimisation functions

In practice, the vast majority of new combi boiler installations in London comply with Boiler Plus by installing a smart thermostat. A Gas Safe engineer installing a new boiler who does not discuss or include a Boiler Plus-compliant efficiency measure is either in breach of the regulations or installing a like-for-like replacement of an existing appliance (which is exempt) — clarify which applies.

Installation Requirements and Costs

Heating control upgrades have varying installation requirements:

• TRVs fitted throughout (replacing manual valves): A plumber's job — no gas certification required unless the system needs to be drained. Typical cost: £30–£50 per valve installed, so £300–£500 for a full set of TRVs on eight to ten radiators including draining and refilling the system.
• Smart thermostat (Hive, Nest, tado): Requires wiring to the boiler. If the wiring connection is to the boiler's low-voltage controls (24V wiring), it does not legally require Gas Safe certification in itself — but many engineers are Gas Safe registered regardless. Typical installed cost: £150–£350 including the smart thermostat unit and installation.
• Zone valve system (two-zone heating): A more significant job requiring pipework, zone valves, additional programmer, and wiring. Typically £600–£1,200 installed depending on the property's layout and existing pipework configuration.