The Kelvin isn’t great at warming up the air. At one point during my tests, I decided to crank the Kelvin as high as it could go and see how long it would take to increase the overall temperature in the room. Over the course of three hours, the air itself warmed up by only about 5 degrees Fahrenheit. In contrast, any of our space heater picks could have done that in roughly 30 minutes through convection heating.
But I must reiterate that this is by design: Far infrared is great at heating objects—but not air—at a lower wattage. And that’s exactly what the Kelvin does. As long as you’re somewhere within the Kelvin’s broad line of sight, the light waves will keep you feeling warm and radiant. But if you’re hiding around the corner of a wall, or if you’re expecting the air itself to feel warm and toasty, you may be disappointed.
The glass surface gets uncomfortably hot to the touch. When I first plugged the Kelvin in, my insatiably curious 4-year-old did what he does best: He impulsively grabbed at this shiny object. Then he yelped in pain.
Don’t worry; he was ultimately fine. But he hasn’t tried to smear his fingers on that glass again.
Later on, when he wasn’t around, I measured the surface temperature of the Kelvin at around 175 °F. It isn’t the absolute hottest space heater I’ve ever tested (that distinction belongs to the wall-mountable but not infrared De’Longhi HMP1500 Mica Panel Heater, which reached a whopping 304 °F), but it is still pretty high up on the list.
It’s also a lot hotter than any other glass object in the house, and it has no obvious visual indicator to caution you when the heater is on. The product manual does warn about this, noting that a “key benefit” of the panels is that you can mount them higher on the wall, thus “reducing the likelihood of accidentally touching them or falling against them.”
The remote sensor is also not great for kids (or pets). As helpful as the sensor is, its ping-pong-ball-like appearance can be another dangerous temptation. My 4-year-old thought it was a toy and kept trying to steal it, and another Kelvin owner I spoke with said they had a similar experience. I can imagine that some pets may be tempted to chew on it, as well. Best to keep the sensor in a place where curious creatures can’t reach it.
The Kelvin takes up a good amount of wall space, which can make it difficult to place. Unless your home aesthetic is staunchly minimalist, finding a place to hang the Kelvin that isn’t already occupied can be difficult.
I was fortunate to find a place in our bedroom for the standard-size Kelvin, which measures a little over 3 feet wide and about 1.5 feet tall (the company also sells larger panels that are about 4 feet by 2 feet). Our 1,200-square-foot home had only one other spot where the panel could have fit, unless we decided to rearrange all of our artwork and other decorations.
Even after you find a space for the Kelvin, you still have to deal with the glare of the glass. “It blends in nicely, but there’s still that refraction on it,” said Mike Finnegan, another Kelvin owner. “Like if you’ve got it near a window, you can see the reflection of the outdoors on it. So it always kind of sticks out in some way.”
The semipermanent installation requires putting some holes in the wall. Normally when I test space heaters, I just place them on the floor in the middle of a room and then put them away when I’m done. But the Kelvin requires a little more planning: You need to use a jig to drill anchors into the wall and then hoist a 20- to 30-pound sheet of glass up onto the screws.
That may sound like a reasonable feat if you, like me, are handy and able-bodied. But it could be a genuine challenge for some people. As Kelvin owner Mike Finnegan said to me: “If you can’t mount a TV by yourself, you probably can’t mount one of these.” Or at the very least, you’ll need some help.
The unsightly power cord hanging from the heater is less than ideal. As with most space heaters, the plug on the Kelvin comes with about 6 feet of slack on the cord. That might work for something standing on the floor, but it starts to get complicated when you’re hanging something 3 or 4 feet up on the wall.
Ideally, you’d be able to install your Kelvin right above an existing wall outlet. But even then, you’d still need to deal with the dangling cord. You could try to hide it with a wall-mounted cord cover, for a slightly less conspicuous result.
As with a lot of smart-home devices, the app is still a work in progress. The Kelvin may resemble a giant iPhone, but you’ll find no touchscreen display here. If you want to do anything more than turn it on or off, you have to download the Boldr app. Like a lot of other smart-home apps, it has a nice user interface and offers basic functionality, but it’s still prone to glitching and other frustrations.
The scheduling feature, for example, allows you to set your preferred temperature at different times of the day—but you have to go through and manually enter each individual day separately. The app also has a built-in “tariff” feature that allows you to track or limit your energy use; unfortunately, this feature crashed every time I entered my local electricity rate. (The app has an optional AI component that’s supposed to be able to read your electrical bill, but that has never worked for me, either.)
Boldr acknowledged that the app is still a work in progress—something that isn’t uncommon among smart-home startups. However, the two customers I spoke with said that the company was helpful and responsive when they reached out for tech support, and that the app had come a long way from when they started using it.
Did I mention that the Kelvin is expensive? The Kelvin’s $400 price tag makes it much more expensive than most other space heaters out there—though its lower energy usage could help you save some money in the long run.
Within the broader category of infrared panel heating, however, the price of the Kelvin isn’t that much of a standout. Herschel infrared panels are similarly priced, and while they don’t have the same glass finish, they do come with a generous 10-year warranty, in contrast to the Kelvin’s two-year warranty. Some people really like the Herschel panels, while others have complained that, well, they don’t heat the air itself enough or that you feel the heat only when you’re directly in front of them.
You can also find some slightly smaller 400-watt panels at retailers such as Home Depot for about $100 less than the Kelvin, though again, these models don’t have the same glass finish to help with the heat dispersal. And you might consider saving another $100 or more on top of that with any of the various cheap infrared heating panels available on Amazon—but we didn’t find any models there that looked convincingly effective, let alone safe.
