When I worked in New England it seemed we were always 6 months behind; the indoor work happened in summer and the outdoor work happened in winter. Most years I spent a couple of months wearing felt-lined boots and even once broke down and bought some electric socks. It was a long time ago and the ones I got were terrible; the heating element was a stiff uncomfortable wire in the toe area and the socks were connected by wire to a belt-worn battery pack. They were ridiculous and I eventually threw the things out
If ThermaCELL heated insoles had been around I would likely have tried them—though they couldn’t have been because the technology they use did not yet exist.
The insoles contain a rechargeable Lithium-Ion battery and are controlled by a remote you can keep in your pocket. There’s no bulky battery pack or wires to deal with. All you have to do is swap these out with the insoles that came in your boots.
There are two models of ThermaCELL insoles, the original Heated Insoles and the more recently released (2014) ProFlex Heated Insoles. ProFlex insoles have removable batteries and are said to be more flexible than the originals. In both models the heating elements are under the ball of the foot and toes and have three settings controlled by a wireless remote: no heat, low (100 degrees F), and high (110 degrees F). By design, the maximum temperature is not very high because you don’t want your feet to sweat. The idea is to provide just enough heat that they don’t get cold.
The original Heated Insoles must be removed from your boots for recharging and connected by wire to a charger. The batteries in the ProFlex install from the top and can be removed without taking the insoles out of your boots. They can then be charged in a supplied wall charger or any USB port—including the kind that plugs in to the aux power receptacle in vehicle. The batteries in either model are said to take 4 hours to charge and be able to power the insoles for up to 5 hours. If that’s true, you could buy a second set of batteries for the ProFlex insoles and charge the spares in less time than it took to run the other packs down. As long as you had power for charging and a place to sit down and swap batteries you’d be good to go.
The insoles come in five sizes, S thru XXL. They’re made from polyurethane and can be trimmed to fit your particular boot.