Next winter will be expensive: How much energy do smart thermostats save?

Next winter will be expensive
How much energy do smart thermostats save?

By Klaus Wedekind

Smart thermostats can help reduce energy use and heating costs, with manufacturers promising savings of 20 percent or more. In principle this is possible, but it very much depends on the individual case and you can often achieve equally good results with simpler methods.

Even before the Ukraine war, it made sense to save energy for heating. But with looming shortages and steeper price increases, many people are now thinking about it more seriously. Smart thermostats are a relatively simple and quick to implement means of heating in a more controlled and therefore more efficient way. Manufacturer Tado°, for example, puts its savings potential at an average of 22 percent. In principle, this may be possible, but this is not the case for all households. One of the deciding factors is how the warm-up has been done so far.

Limited savings potential

In 2019, Stiftung Warentest tested the potential of ten different smart thermostats and saw savings of five to eight percent. That doesn’t sound like much. But in light of exploding energy prices, this can make a noticeable difference to the family budget. The more expensive the fuels, the more profitable it is to buy smart thermostats.

At prices between €40 and €70 per controller, for example, an apartment with six radiators can add up to €240 to €420, not including accessories such as window sensors, room thermometers or spare batteries. If you don’t already have a connected home, you may need to invest an extra $50-$100 in a smart home hub.

In the heating season 2020/21, according to “Heizspiegel”, this would not have paid off so quickly for a small single-family house with 110 square meters of floor space and gas heating at an average cost of 650 euros. But for the current season, the costs have almost doubled to 1,250 euros. The price of heating oil has fallen again recently, in part due to the release of US stocks. However, currently 100 liters are around 135 euros, more than double what it was a year ago (60 euros).

Profitability increases with higher energy prices


Especially with gas, heating costs have increased tremendously.


At such prices, the purchase of smart controllers can already pay off with savings of sht percent. In some cases, however, more can be obtained. At the time, Warentest assumed that “residents have a typical eight-hour workday and want to return to a warm home.” But since the beginning of the corona pandemic, many people have been working from home and would like to continue to do so, at least in part. Also, there are much more detailed gradations than hot in the evenings and mornings, and cold otherwise.

According to the consumption center, each degree less supposes a saving of around six percent. So if you wear a light sweater instead of a T-shirt at night or snuggle under a blanket, power consumption is significantly reduced. However, it should not be exceeded, because below 16 degrees there is a risk of mold formation. It is often more expensive to bring a completely cool room to room temperature than to continue to warm it moderately when you are away.

More accurate and convenient smart thermostats

Another advantage of smart controllers is their accuracy. A conventional thermostat only allows you to program a value between 1 and 5. Level 1 corresponds to around 12 degrees, each additional level around 4 degrees more. Smart thermostats, on the other hand, allow you to regulate the temperature within half a degree.

A big plus point is the ability to set exact time periods. For example, on weekday mornings you can heat the bathroom for exactly the 30 minutes you spend there before you leave home. Maybe it should be a few degrees higher before bed, the rest of the time it can be cooler in there.

In addition, network thermostats offer comfort functions that make energy saving more enjoyable. For example, you can operate and configure them through an app or laptop on the go. Many devices also stop automatically when you open a window or leave the house.

Thrifty users save a little more

There are other situations where a smart thermostat can prove its worth. But you can see from the examples that most of this can also be done manually if you have the discipline and are not too forgetful. For the savings potential, it is therefore decisive how you improve the previous heating behavior through the purchase of smart thermostats.

Much greater savings potential lies in better insulation of the building or a renovation of the heating system, among other things. In your own home you can program night setbacks, etc. in the boiler. For renters, on the other hand, switching to smart thermostats can definitely pay off in light of the huge increase in energy prices. However, if you’ve been heating sparingly so far, the added benefit isn’t that great.

AVM Test Winner

If you opt for smart thermostats, you should not only look at the price, but also the quality. The best solution for Stiftung Warentest was the AVM Fritz DECT301 (approx. 55 euros) for Fritzbox owners. The deciding factor was the easiest handling (grade 1.9) among the test candidates, and an additional smart home base is not required. The device works without window contacts, but according to the product test, it also accelerates heating well without it.

When it comes to heat regulation, the Devolo Home Control (approx. 60 euros) showed the best performance (1.5). However, because the handling was only rated “satisfactory” (3.0), the thermostat only ranked third in the product test comparison. it was outclassed by the FritzDect 301 in terms of handling (2.1).


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