Why the 19 °C Rule Is Giving Way to 20 °C Smart Thermostats

For many decades, households relied on one figure to determine the right warmth for their homes. That approach is rapidly becoming outdated: experts increasingly prioritise comfort, building performance and intelligent controls over an inflexible thermostat target.

The end of the fixed 19 °C rule

Across much of Europe, the well-known 19 °C standard emerged during the oil crises of the 1970s. At that time, heat escaped easily from properties with poorly insulated walls, single-glazed windows and inefficient boilers. Heating rooms beyond that level could mean excessive fuel consumption and sharply rising bills.

The situation is now very different. Insulation requirements have advanced, while modern windows retain heat rather than letting it escape. Digital thermostats measure temperatures accurately instead of estimating them. Consequently, specialists no longer regard 19 °C as a universal ideal, but rather as a benchmark from an earlier era.

One degree of difference can shift a household’s annual energy use by around 7%, with a direct effect on gas bills and emissions.

Energy experts at organisations including ENEA and the Polytechnic University of Milan suggest a small revision: 20 °C is a more practical guideline for living spaces in refurbished or newer homes. Although the difference appears slight, it represents a revised compromise between efficiency and comfort.

Why 20 °C is becoming the new benchmark

Temperature is not the sole factor behind human comfort. Humidity, air circulation, surrounding surfaces and clothing all affect whether a room feels warm or cold. Engineering and thermodynamics specialists note that the body copes better with gradual variations than with major temperature differences between rooms.

When people are sitting, working on a laptop or watching television, a living room at 20 °C makes it easier for the body to maintain its natural 37 °C temperature. Muscles are less likely to tighten, and the body need not respond so strongly to cold draughts. Meanwhile, warmer walls, floors and windows lessen the cold sensation that frequently leads residents to use additional heaters.

There is a benefit for the condition of the building, too. At approximately 20 °C, alongside balanced humidity, surfaces remain drier. This reduces condensation on cold corners and window frames. In turn, less condensation can result in fewer mould patches and a lower likelihood of spores spreading through the air.

Raising the setpoint by just 1 °C may prevent people from turning to electric fan heaters or constantly moving to smaller rooms, which often wastes more energy overall.

Room-by-room comfort targets

Rather than aiming for an identical temperature throughout the property, professionals now refer to comfort ranges. European energy agencies and building engineers commonly use the following recommendations:

Room	Suggested temperature
Living room / home office	20 °C
Bedroom	16–18 °C
Hallways / circulation areas	17 °C
Bathroom	22 °C (for limited periods)

These figures should be treated as an initial guide rather than a final judgement. Older, draughty properties may feel colder at the same reading, particularly where floors and external walls remain very cold. Conversely, well-insulated flats can often remain pleasant with a slightly lower thermostat setting.

Smart thermostats replace one-size-fits-all rules

The key change is not simply the figure displayed on the thermostat, but the way it can respond to everyday routines. Modern digital thermostats, including smarter connected models, enable households to heat rooms differently at different times of day.

Regulators such as ARERA in Italy state that using scheduling features correctly can reduce yearly heating costs by up to 15%. The idea is straightforward: heat spaces when they are occupied, then reduce the temperature gently when they are unused.

• Smart thermostats can be managed remotely by phone, allowing users to postpone heating when they work late.
• Presence sensors identify empty rooms and prevent them from being held at full comfort temperature unnecessarily.
• Connecting systems to heat pumps or solar thermal panels can move some heating demand to cleaner, lower-cost energy sources.

This does not require every household to buy the newest technology. Even a straightforward programmable thermostat can reduce waste when used regularly. A basic routine, with lower temperatures overnight and modestly warmer settings in the early evening, already moves away from the inflexible 19 °C approach and aligns heating more closely with actual demand.

The trend moves from one fixed rule for all homes to many small, informed choices made room by room and hour by hour.

Practical examples for a typical week

Take a family with conventional office hours. They could set the living room to 20 °C from 6:30 to 8:30 in the morning, allow it to reduce to 17–18 °C while nobody is home, then increase it again between 5:30 and 10:30 in the evening. Bedrooms may remain at 17 °C during sleep, with a small early-morning increase for anyone particularly sensitive to cold.

For people working remotely, the schedule is different. During daytime hours, the home office or main living space becomes the priority area and may stay at 19–20 °C. Rooms used less often, including spare bedrooms, can be reduced to 16–17 °C without a meaningful reduction in comfort.

The new balance between household comfort and budgets

When they are properly insulated, modern homes can maintain 20 °C with shorter boiler operating times than was previously possible. Double or triple glazing, insulated lofts and sealed window frames reduce the continual heat loss that once characterised winter. However, energy prices are still unpredictable, and many households monitor spending carefully.

Smart meters and digital gas meters, which are now fitted in millions of homes across Europe, allow residents to connect thermostat choices to real energy use. Rather than depending on broad rules of thumb, households can track from week to week how a 1 °C adjustment changes consumption.

Tracking consumption for two or three weeks at different setpoints often gives clearer guidance than any generic rule from decades ago.

Specialists commonly advise making limited, gradual adjustments: change the thermostat by half a degree, observe the result for several days and assess whether anyone notices. If comfort remains satisfactory, a further half-degree reduction may be possible. If someone feels cold while working or reading, maintaining the temperature and improving insulation or adding clothing layers may be the better option.

Helpful habits to reduce waste without feeling cold

The thermostat setting is only one part of the overall picture. Everyday behaviour determines whether a heating system operates efficiently. Energy advisers often suggest:

• Bleeding radiators at the beginning of the heating season to ensure hot water circulates correctly.
• Positioning furniture away from radiators so that heat flow is not obstructed.
• Shutting blinds or drawing curtains overnight to reduce heat loss through windows.
• Ventilating for a short period with windows fully open instead of leaving them slightly open for extended periods.

Such simple measures can often keep households comfortable at 20 °C without raising the setting further. They also make people less likely to use extra electric heaters, which generally cost more for each unit of heat and place additional strain on electricity grids during peak periods.

Beyond numbers: health, behaviour and building quality

Moving away from the strict 19 °C rule also raises wider questions about health and housing standards. Very cold homes can worsen respiratory conditions, particularly for older people and children. Overheated homes, meanwhile, dry the air, irritate mucous membranes and increase fossil fuel use.

Public health guidance in several countries now presents 18–21 °C as a comfort and safety range for occupied spaces instead of a single fixed target. Within this range, the most appropriate setting depends on insulation levels, the age of those living in the home and even cultural expectations around indoor clothing.

The issue is also linked to the climate transition. As heat pumps and district heating progressively replace gas boilers, heating-control methods will change once more. Heat pumps perform more efficiently at stable, moderate temperatures than during large fluctuations. This may encourage households to maintain 19–20 °C for longer, alongside substantial insulation improvements.

For the moment, experts deliver a broadly consistent message: the former 19 °C limit no longer reflects modern homes. A flexible, evidence-led strategy is more suitable. Combining moderate temperature settings, smart controls and straightforward maintenance can help households safeguard comfort and budgets while reducing their environmental impact.