According to science blog Physorg, two Italian scientists, Andrea Rossi and Sergio Focardi of the University of Bologna, claim to have developed a cold fusion reactor. Reportedly, the reactor is capable of producing 12,400 W of heat power with an input of just 400 W.
As the article explains, "[...] when the atomic nuclei of nickel and hydrogen are fused in their reactor, the reaction produces copper and a large amount of energy". The scientists also say that one reactor has been running continuously for two years, providing heat for a factory but gave little detail or evidence about this case.
The article includes a video and a lot of scepticism.