Hotronic Footwarmer S4 Review

An essential part of a successful day of skiing is staying warm. With the wind, snow, and frigid temperatures all around you, you need to prepare for all types of weather.

While wearing a lot of gear can help, if you pile on too much, it can negatively impact your performance and how well you can move. Thankfully, there are small and slim solutions that can keep you warm without adding too much bulk. Of course, I am talking about foot warmers.

In particular, this guide will take a look at the Hotronic Footwarmer S4, and help you decide whether it is the right choice for you. Keep reading to learn more about the pros and cons of this footwarmer, and other similar alternatives to consider.

Quick Summary

According to the manufacturer, the temperatures this product can reach are: 84-98 degrees F on the first setting, 107-121 on the second, 122-138 on the third and 158-173 on the fourth.

This product is incredibly easy to install and switch from boot to boot. The heating element is easy to attach to the soles, and can be done in seconds. Simply attach the battery to the back or side of the boot, plug in the cables and put the insole in the boot.

Everything that you need to set up and enjoy your new foot warmers comes in the package. This includes the battery packs, heating elements, covers, insoles and the charger used to recharge the batteries.

Why Trust Me

As a snow sport enthusiast, I know a thing or two about cold weather and trying to remain comfortable in it. If there is a product or device used to help people stay warm (whether skiing, hiking or just going for a walk), there is a good chance I have tried or considered it. I have researched and discovered its performance traits and other people’s experience for this specific foot warmer.

Detailed Review of Hotronic Footwarmer S4

Multiple Heat Settings

One of the best things about this foot warmer is that it comes equipped with multiple heat settings. There are three basic heat levels, and then a fourth option for a quick burst of heat when you really need it. At the lowest setting, the foot warmers will give off a subtle heat that can last all day.

At the highest, your feet will get warm and toasty in even the lowest of temperatures. Most people seem to prefer around the second level, for noticeable warmth that doesn’t drain the battery too much. With so many different choices, these foot warmers offer a lot of versatility no matter the kind of weather mother nature throws at you.


The sizing of your foot warmer is incredibly important. If it doesn’t fit your boot, or is uncomfortable due to incorrect sizing, skiing on it can be a nightmare. Thankfully, the Hotronic S4 has you covered. These warmers actually come in two varieties when it comes to sizing. The universal option allows you to cut down the insole to the correct size for your feet.

The custom option comes in a variety of different sizes, so you can simply choose the one that fits best. While the insoles aren’t the most comfortable, they aren’t likely to negatively impact your performance either. This is because the batteries attach to the side of the boot, which keeps them out of the way.

Battery Life

The battery life of a foot warmer is a crucial part of how effective it can be. If a warmer only lasts a few minutes before its battery dies, it wouldn’t be much use on a day-long ski adventure. Thankfully, this product doesn’t have that problem, and the battery life of these foot warmers is actually quite impressive.

On the lowest setting, these things can last over 16 hours according to the manufacturer. Even if you crank it up to the third level, which is plenty hot for most people in most temperatures, the batteries will still last over 5 hours easily. Over time, the battery might lose its effectiveness a little, but that’s to be expected with any battery operating in cold environments.

Durability and Build Quality

One area where these warmers struggle a bit is with their durability and build quality. They are not horrible by any means, but for one of the more expensive foot-heating options out there, some were a little disappointed.

The design is not very rugged and might struggle to stand up to prolonged use and regular wear and tear in some cases. As skiing can be a pretty rugged sport full of a lot of falls, a little more durability and some stronger materials used in construction would be nice.

What I Like

The first thing I like is the multiple heating levels offered by the product. Whether you only need a little warmth, or a lot, these have the right heat for your feet. The battery life is also quite good, and you won’t need to worry about it running out of juice anytime soon.

Another thing worth mentioning is the overall design of the product. While some foot warmers will have the battery in the heel or below your feet, this product is a little different. Instead, the battery is attached to the outside of the side of the boot. It is easy to install and makes it simple to switch it over to another boot if need be.

The fact that they make sizing easy is another benefit of this warmer. Whether you get your own size by ordering the custom version, or simply cut down the universal to size, these can easily fit into a variety of different boot and shoe sizes.

What I Dislike

The durability of this product is one area that could use some improvement. While some people have enjoyed this product for years, others have hardly had them last a week. The most common issue is the heating cords and cables breaking or tearing. They are quite flimsy and aren’t the most durable.

A slightly stronger cable with a more rugged design and connection would be something that many would like to see in a future iteration. The price and value is also another thing that might turn some people off. The product is quite expensive, and while it works well, there are cheaper options out there for anyone who might be a more casual skier.

While they aren’t all that expensive compared to other ski gear, they are quite a bit more pricey than other similar products.

The Alternatives

This foot warmer is a popular and solid choice, but it isn’t the only one available on the market. Here is a look at a few alternatives.

  • Snow Deer heated socks – While these aren’t a foot warmer in the traditional sense, they can still keep your feet warm on the slopes. The rechargeable heating elements cover your whole toes, and the product comes with various heat settings. The material is soft, and the batteries are secured in a pocket on the side of the socks.
  • HeatMax Toasti Toes Foot Warmer – Coming with 40 pairs, this is a good choice for those who prefer single-use heat. These foot warmers are small, incredibly thin, and heat up fully in less than half an hour. They can give off up to 8 hours of heat, and they are completely safe and natural. They are also very affordable and with so many in the package, have the potential to last you many ski trips.
  • Warmfits heated insoles – If you like the style of the Hotronic S4, but want something a little more economical, these insoles from Warmfits are a good choice. While the battery life isn’t quite as strong, these insoles can be customized in terms of size and the battery is easily secured on your ankle. Charging them is very easy and they can reach up to 120 degrees F.

Final Verdict

If you are in the market for a versatile foot warmer for everything from mild to subzero temperatures, the Hotronic Footwarmer S4 is an option for you. They can last all day, finding the right size is a breeze and they do a good job of staying out of your way.

While they come with a fairly steep cost when compared to other warming options and aren’t perfect, they are a great way to ensure you stay warm, no matter where your adventure takes you.

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  • Nancy

    What Chuck said. I emailed Hotronic asking about S4+ batteries and whether one could use the new lithium batteries with old system, or whether other compatible batteries are available. The response: “The new batteries are not backwards compatible with any of the previous components due to the new product being upgraded from top to bottom. Because the S4+ were nickel metal hydride we will not be able to have any more produced, so they are considered obsolete and end of life at this point … There is no substitute as they would also be nickel metal hydride or use the older components.” Given that information, I would not buy a new set of the discontinued S4 heaters, but instead would buy a boot heater that is not discontinued (unless you get a really good bargain and don’t care if you can’t replace batteries. This might be fine, as I have found the wires on the heating elements usually break before the batteries die)

    • Christine

      Good to know Nancy, and thanks for sharing your experience with these heaters. Working on getting this article updated to reflect so appreciate the feedback!

  • Chuck

    Been using Hotronic S4 heaters and love them, until just recently. Appears the batteries are no longer made, and when I found some replacements online (new in OEM packaging), they must be older batteries that have been sitting around for a couple years. While they appear to charge normally, they barely last 1/2 as long as they should. Looks like no options but to replace all my boot heaters, and I have about 5 pairs. That said, I’ve made the heating elements much more durable by just wrapping the fat cords with gaffer’s tape when I install them, so the tape takes all the punishment.

    • Christine

      Hey Chuck,

      That’s a bummer to hear about the batteries. I hope it’s not an ongoing issue, but thanks for sharing. I’ll get the article updated to reflect that issue if needed. Keep those feet warm, and hope you’re having a solid winter.