Article Wahrm in the Parool: Is personal heating the future?

Wahrm's body warmers and hoodies are powered by a battery that can be easily charged at home, after which they last for two to four hours, depending on the capacity and the set temperature. Stapper, who previously founded the sustainable clothing brand Bamboo Basics, sold around five hundred heated garments this winter.

He's received enthusiastic responses – from home workers who work alone on their laptops during the day and don't want to heat the entire house, but also from users who take the heated clothing outside. "On the golf course or when they're on the sidelines early in the morning at their children's sports games." He also understands how the clothing can be useful when couples disagree about the room temperature. "When one person is always warm and the other is always cold."

Overcrowded electricity grid

This makes heated clothing seem like the next step in a longer-term development. When everyone was confined to their homes all winter during the coronavirus pandemic, heated blankets and pillows, which also provide a cozy glow through infrared radiation close to the body, were already growing in popularity. Furthermore, infrared panels are even being used in some homes to transition away from natural gas.

Is personal heating the future? And can we really save a lot of energy with it?

While there's not much research yet, infrared panels have indeed been shown to reduce energy consumption. This is the conclusion of consultancy firm W/E, based on the experiences of sixty households using the panels for heating. It's worth noting that daily use—that is, heating habits—significantly influences actual energy consumption and perceived comfort. The panels take little time to start up, but the heat dissipates more quickly than with central heating that heats the entire room.

On the other hand, energy costs can rise significantly if the panels are used frequently. They also push the already overloaded electricity grid to its limits, potentially requiring a more powerful electrical connection with higher fixed charges. On the other hand, the installation costs of infrared panels are low. Therefore, the conclusion is that they seem particularly suitable for small or well-insulated homes.

Small apartments, on the other hand, are quite common in a densely populated and expensive city like Amsterdam. If you're often away from home, infrared panels can be very useful. They're also ideal as supplementary heating in a place that needs to be a bit more comfortable for part of the day, such as a study. Some satisfied users have even installed them under their desks, so the heat radiates over their thighs while they work.

Suppliers of heated blankets and pillows are also eager to claim they save energy. Market leader Stoov, for example, states in an "impact report" that the pillows cost only 1.7 cents per charge. In contrast, Stoov claims you can save €153 per year "if you turn down the thermostat by one degree and use a Stoov."

Stoov also acknowledges that there's no scientific research supporting the claimed energy savings, admits Teun van Leijsen, who founded the company in 2014. He does, however, point to research by building physicist Dionne Limpens. She earned her doctorate in 2006 for her work on a heating system for historic churches that pay a fortune for their gas bills. It proved cheaper and even more comfortable for the churchgoers when only the pews were heated.

Electrically heated scarves

Van Leijsen cites heated car seats as another excellent example of personalized heating. These inspired the idea for Stoov's heating pads. Efficient heating is also essential in electric cars, if only because it would otherwise compromise battery capacity and range. "Creating heat is expensive. That's why we mitigate that as much as possible with heated seats."

Stoov's popularity seems to indicate that consumers associate heated pillows and blankets with energy savings. Stoov's rapid growth, and a long line of imitators offering the same pillows and blankets, coincided with rising energy prices in recent years. However, according to Van Leijsen, sales of heated pillows were already skyrocketing before the coronavirus pandemic and the energy crisis.

The next step Stoov took last year seems significant. After heating pads and heated blankets, the introduction of electrically heated scarves followed in 2024 – bringing them even closer to the skin.

Because that seems to be the general trend, paralleling the development of power banks that are becoming increasingly powerful, cheaper, more compact, and faster to charge: heating is getting closer to home. Scientists from Vrije Universiteit Amsterdam (VU University Amsterdam) noticed this too, as did the "action network" GasTerug, which was formed in the Amsterdam region after the Russian invasion of Ukraine with the aim of reducing energy consumption. Together, they therefore conducted research this winter into the possibilities of "personal heating."

Forty participants received a heated vest—not from Wahrm, by the way, but from the outdoor brand Bertschat. The study participants were primarily elderly, low-income earners, or Amsterdam residents vulnerable due to a chronic condition. The results will be further studied in the coming months, but the initial indications are positive, says VU professor of exercise physiology Hein Daanen. "Some people say they'd happily turn the heating down two degrees, but others are so used to it that they still leave the thermostat at 19 degrees."

"Overall, we have a positive outlook," says Daanen. "Some people don't want to give up their jackets anymore." Based on initial calculations by the students involved, the savings are estimated at hundreds of euros per year, although these naturally vary from household to household, depending on factors such as heating habits and insulation. An important caveat is that the room temperature shouldn't drop below 15 degrees Celsius, as this can cause the home to become so damp that mold problems can arise.

Vulnerable health

The scientists also looked at the participants' comfort and whether they were less affected by the cold. Warmth, for example, helps with stiff joints and inflammation, and stimulates blood circulation. For participants who were vulnerable due to osteoarthritis or had recently undergone major surgery, the vest initially appeared to have a beneficial effect.

"It had a particularly pain-relieving effect on people with rheumatic complaints," says Robert Thijssen of the Sigra healthcare network, a partnership of hospitals and nursing homes in the Amsterdam region that is eager to further explore the potential of the heated clothing. Nursing homes always have their thermostats set very high, and the vests might help to reduce that. It was also encouraging that people with low-income families and rheumatic complaints went outside more often thanks to the 'electric body warmers.' "That's what we want, of course: more exercise and social interaction."

Thijssen even thinks about the homeless. "The vest could be their lifesaver during cold winters." At the same time, the need to charge the vest could keep them in touch with emergency services.

With a purchase price of at least €130, it seems unlikely the vests will be used to combat energy poverty among low-income residents who can't afford their energy bills. However, Thijssen does consider it possible that housing associations will distribute them if a street is struggling with renovations to include double glazing. Or, like a mobility scooter, they could be provided by the municipality if Amsterdam residents, due to their fragile health, could easily use them.