The thermostats regulate the operation of heating and cooling systems in such a way that the temperature is kept constant at the specified desired level. The evolution of technology has highlighted the usefulness of these devices, while at the same time introducing additional parameters that we should take into account before choosing the right one.

1. Compatibility with the heating/cooling system

Each thermostat is designed to connect to specific types of heating/cooling systems. Therefore, your new thermostat should be listed in its technical specifications as compatible with the system installed in your space (e.g. a boiler system, heat pump, or convectors).

SkroutzTip: Please note that some thermostat models can connect to and control more than one heating/cooling system simultaneously.

2. Installation type

Before looking at the features, consider where the thermostat will go. This determines whether you’ll need to cut into the wall, run a cable, or simply place it on a surface.

• Wall-mounted: attached to the wall without requiring a recess. A good choice when the cable is already routed externally or you want to avoid drilling into the wall.
• Recessed: installed in a box inside the wall and sits flush with the surface, like a light switch.
• Plug-in: plugged into an outlet to control the heating device connected to it. No installation is required, but the power limit specified in the product specifications applies.
• Tabletop: placed on a surface and easy to move. Many models are wireless.

SkroutzTip: Before choosing, check whether there’s already a box or wiring at the installation point. This will help you determine whether a recessed model can be installed without additional work.

3. Power supply: mains or batteries?

The thermostat needs power for its display and sensor. Its power supply determines how it is installed and how often you’ll need to attend to it.

Mains-powered thermostats connect to the room’s power supply, so you don’t need to replace batteries, but they require wiring at the installation point. Battery-powered thermostats can be placed wherever you like, without a power cable, but you’ll need to replace the batteries. If they run out, the thermostat won’t work.

Choose a power supply option below to see the corresponding models.

4. Bimetallic or Electronic

Bimetallic thermostats regulate the temperature using a bimetallic strip (two joined metals that behave differently when heated or cooled). More specifically, the heating system switches on/off when the bimetallic strip bends due to a change in temperature from the desired level. However, for the bimetallic strip (and therefore the thermostat) to detect this temperature change, it must be significant (around 3oC). You can find them in the list of analog thermostats, along with other models that are adjusted manually.

On the other hand, electronic thermostats use electronic sensors to monitor room temperature and switch the heating/cooling system on when the temperature changes slightly from the set desired level. It is worth noting that, in several electronic thermostat models, their “sensitivity” to temperature changes can be adjusted. In other words, you can set whether a change of around 0.5oC will be detected by the thermostat or not.

Because they respond more immediately to changes in room temperature, electronic thermostats are more efficient than bimetallic ones: they keep the temperature close to the desired level for longer, avoiding large fluctuations while also reducing system energy consumption.

5. PID or On/Off

On/off thermostats allow the heating/cooling system to operate until they detect that the room has reached the desired temperature. They then stop the system and restart it when they detect that the temperature has once again deviated from the desired level. The drawback of this operation is that the heating system may overheat or underheat the room, depending on how quickly the thermostat detects these deviations.

PID thermostats are equipped with a microprocessor that:

• Compares the desired and current temperatures at regular intervals
• Records how quickly the difference between the desired and current temperatures changes
• Predicts future deviations

Based on this analysis, the thermostat controls the heating system in a way that allows it to reach and maintain the desired temperature with as few fluctuations as possible.

6. Scheduling capability

Programmable thermostats allow you to set the desired temperature for different times of day and on different days. This means you can enter the temperature you want in your space at any time of day, so you don't have to keep turning the heating/cooling system on and off or changing the temperature. Depending on how much flexibility each thermostat offers for setting the schedule described above for each day, they can be divided into the following categories:

• 5-2-day program: Supports two different programs. This type of thermostat is designed for people who follow the same schedule on weekdays, with a different but consistent schedule on weekends.
• 7-day program: Allows you to set a different program for each day of the week. Newer models in this category support copying a program from one day to another. This makes setup easier when the schedule is the same on multiple days.
• 5-1-1-day program: Supports three different programs. This type of thermostat is designed for people who follow the same schedule on weekdays but have different schedules for each of the two weekend days.
• 1-week program: Supports just one program, which is followed every day of the week.

SkroutzTip: In addition to the categories mentioned above, consider how many periods per day let you set a different temperature. There are usually 2 to 4 periods per day.

SkroutzTip: Programmable thermostats have a display that shows all the relevant readings digitally.

Non-programmable thermostats only let you set the temperature to your desired level, which remains unchanged until you adjust it manually. They are designed for people who spend most of the day at home. Non-programmable thermostats can be classified as digital or mechanical.

7. Type

• Digital (non-programmable): They are equipped with a display that shows all the relevant readings digitally.
• Analogue: The temperature is adjusted manually using a mechanical control. They are intended for people who are unfamiliar with digital displays and prefer to operate the device using a rotary knob.

8. Wi-Fi & smart features

If you want to change the temperature without getting up from the couch or while you’re away from home, you’ll need a thermostat with an internet connection.

Wi-Fi thermostats connect to your home router and are controlled through an app on your phone. This lets you change the temperature or schedule from anywhere. With smart models, the app usually also lets you set a schedule.

Many models are compatible with voice assistants such as Alexa, Google Home, and Apple HomeKit. Check the specifications to see which assistants each model supports.

SkroutzTip: Check whether the model supports your Wi-Fi network (e.g. 2.4 GHz or dual-band) and whether the app requires an account.

9. Additional Features

1. Override the set schedule - If the programmable thermostat supports this feature, you can override the programmed operating schedule permanently or for as long as you wish.
2. Keypad lock - If the thermostat supports keypad locking, you can prevent intentional or accidental changes to the temperature setting and programmed schedules.
3. Automatic switching between cooling/heating modes - This feature refers to the thermostat's ability to switch automatically between cooling and heating modes when the room temperature exceeds a set threshold.
4. Backup battery - If the thermostat is powered by the property's mains electricity, a backup battery helps preserve the programmed settings in the event of a power outage.
5. Remote control - Some models can be operated using a compatible remote control within the room where the thermostat is located. To control it from your phone, see the section on Wi-Fi and smart features.
6. Humidity measurement - Some thermostat models measure not only the temperature but also the current humidity in the room.

Don't forget! Choose products that suit your space and heating system, taking into account compatibility, installation method, power supply and the features you'll use. Before making a decision, read reviews from other users of the models you're interested in.

Also discover the best room thermostats for every need.

This article was created with the help of AI and reviewed and edited by the Skroutz team.