A Zippo Hand Warmer costs about A$30 on Amazon. It uses about 2o mls of ligher fluid over 12 hours. If lighter fluid has about the same calorific value as kerosene then a litre produces about 9-10,000 watts so 20 mls produces 180 watts which over 12 hours equals approximately 15 watts per hour. You can buy Chinese knock-offs of these Zippo heaters from about US$7 at Aliexpress (and spare burners too. Some folks claim to use metho in them. This is something I must try.
The resting human body produces 80-100 watts so the Zippo represents an addition of about 1/6th to that (17%) which is not at all insignificant – for an energy weight of around 16 grams per day. The Zippo weighs 2.6 oz (74 grams). This is more heat than you could get by adding any comparable weight of extra insulation.
The Wattage of the 2L Ultralight Hot Water Bottle is only about 5Watts (50C loss over about 8.0h) by comparison so the Zippo might well be a better alternative. If you have a spare $30 since it is now winter it might be a good time to try it out!
See Also:
Ultralight Hot Water Bottle
