There are three technologies available. Polymer embedded fabric, Polyacrylamide crystals, and Phase-Change packets. Each has their own advantages and disadvantages. The polymer embedded fabric looks and feels most like a normal vest. The fibers soak up water and cool you by evaporation, so some wind is required. These vests don't hold much water, and therefore have limited cooling capacity. Recharge by soaking for 5 minutes in a large zip-lock bag. Polyacrylamide crystals are the thing that make disposable diapers work, and the latest rage in gardening. The fibers soak up water and cool you by evaporation, so some wind is required. These crystals hold a lot of water. The downside is that the vests will soak up seven to ten pounds of water, if you let them. Recharge by soaking for 10 minutes in a large zip-lock bag. Phase-change packets work chemically, not by evaporation, so these vests work in still air. The phase change packets are good for about 2 hours. However, to recharge the vests you have to cool them down, either by soaking them in ice water or by putting them in a freezer or refrigerator for an hour. So these vests are only good once per day if you're riding. Also, they're quite pricey.
I've used the polymer embedded fabric and the polyacrylimide crystals. The crystals are better.
Two Widder heated vests and a pair of heated grips are about 110 watts total - this is no problem for most bikes, and means you and your passenger ride in comfort down to 35 degrees. I don't think heated arm or leg chaps have much value - if your torso is warm, your body will take care of everything else. But then, I was born in Green Bay. If you're from Honolulu, perhaps you have a different opinion. Some people like heated socks or insoles. I don't need them, and I think the extra wiring is a pain. Heated grips are good because they're always on the bike - your vest and gloves are not always packed.
Heated vests fit quite tightly on you. I wear only a t-shirt under mine, then over it goes a sweatshirt and my jacket. Jacket Liners do not fit as tightly, and therefore are not as efficient at transferring heat. In any case, you want the heat as close to your body as possible, and as much insulation between the heat and outside as possible. Vests also pack smaller than jacket liners, and allow more options in layering when putting on clothes.
|Vest $110 33/35/48w||Vest w/ Collar $130 33/35/48w||Arm Chaps $80 20w||Gloves $90 20w||Chaps $100 33w|
|Vest $140 53w||Jacket Liner $200 77w||Pants $200 44w||Gloves $140 22w||Socks $60 22w|
|Vest $140 45w||Jacket Liner $230 70w|
|Vest $50 22w||Insoles $50 15w||Gloves $50 15w|