What is a Mug Warmer? A mug warmer is an electrical device used to keep mugs and their contents warm, or to pre-warm a mug before introducing a hot beverage. This prevents sudden loss of some of the heat through the cold material, or to keep the contents of a mug warm for prolonged periods of time.
This is done in a similar way to electric thermoses, providing gradual low-wattage heat to sustain an amount of thermal energy in a liquid. These are all electrically-powered but most are battery-powered with a lithium-ion battery and a USB port.
Some of them actually are mugs themselves, or rather, a take on the powered thermos concept, with insulator material. These are a technology commonly found as part of a tech trim package in modern vehicles, but is also available in a standalone form.
The material used may be brushed steel, aluminum or even plastic, depending on build quality. They do need frequent recharges, as they produce heat entirely by wasting electrical current. This is a good product for tea or coffee drinkers who find their coffee going cold on them often. Microwaving coffee and tea repeatedly wastes a lot of energy and will result in its freshness quickly declining. Mug warmers are a cost-effective way for busy people to keep their drinks hot without wasting a lot of energy to do so.