I’ve been a long‑time advocate of heated clothing – for me it is the best way to keep warm inside your home over winter. However, through my own personal testing, and feedback from others, I’ve found that a heated garment may not work too well if it is worn incorrectly.
In particular, if a heated garment is worn as the outer layer over thick jumpers etc it will very likely add no perceptible warmth for the user. The heat is unlikely to penetrate through the other clothes to reach the person’s body and much of the heat energy will simply be lost to the atmosphere.
My rules for wearing heated clothing are: i) wear the heated garment as close as possible to your skin but not in direct contact (eg put on over thermal underwear); ii) get a garment of the right size – it needs to fit nice and snugly so that effective heat conduction can take place; and iii) place one or two layers over the heated garment (eg jumper, dressing gown) so that its heat is trapped in the clothing.
Over the past two winters I’ve been wearing a heated vest which very nicely meets my criteria: i) it has a clever method for size adjustment and so it can be made to fit close to the body; and ii) it is very supple and thin so it doesn’t inhibit the wearing of other layers of clothing.