I suggest for starters using neoprene Dryguy Bootgloves. They cost only about $35.00, they go over your boots, and they work about equally to the Hotronics footbed warmers, in my experience. Because I find the Hotronics footbed warmers to only partly work, I've been using both at the same time, bootgloves and footbed warmers - with good results.
I've used the s3 Hotronics in multiple boots, for the past four years or so. (I'm an older guy with poor circulation - previously I never needed them.) To me they are just so so, by themselves. Using only them, on really cold days my feet still get cold - maybe less cold, but cold. And my biggest problem with them is that on low volume, more race-type boots, they distort the feel and flex of the footbed, and my feet start to hurt. (With more freestyle boots, softer flex boots, and higher volume boots, this is less of a problem, I gather.)
I've found that folks with race boots or low volume boots often use the heated socks, without problems.
Both Lenz and Hotronics seem to work about equally, except Hotronics offers a second type, that wraps around the toes and heats both the top of the toes and the bottom. People I trust tell me that if you have enough space for the wrap-arounds in your toe box (and even many racers do), then this is the superior product - it really heats more effectively. Because I do not have that extra space, I'll be trying the heat from the bottom only socks, and hoping they are at least equal to the footbed versions. Along with my bootgloves.
