Especially, during the last decade the demand for portable power is steadily rising due to the increasing wireless products integrated in our day-to-day lives (cellular phone, personal digital assistant (PDA) and of course the remote control for your television set or VCR). These portable consumer electronics are mainly powered by alkaline batteries, and nowadays more and more by rechargeables. Alternative power sources, like fuel cells and photovoltaic cells, can be used in portable consumer electronics, possibly making them more cost-effective, more environmentally and user friendly. For the consumer industry, the opportunities of these other alternative power sources is unknown, and designers are not known with the state-of-the-art of the technology. Opportunities for short-term but especially long-term developments in portable electronics are in that way overlooked. In this paper, the most interesting power sources available will be compared on the basis of power and energy characteristics, and costs. Emerging power sources like fuel cells are a very interesting alternative for the lithium-ion battery, but the road ahead for it is still long when we look at state-of-the-art developments. Other power sources described and compared are: ether-smog, human power, thermo-electric generators, piezo generators, electro-mechanical devices, photovoltaic cells, micro-fuel cells and micro-combustion engines. (c) 2005 Elsevier B.V. All rights reserved.