A space heater is a device used to heat a single, small area. Space heaters are powered by electricity or the combustion of either gas or a flammable fuel. They pass electricity through a heating element, causing the element to become hot. The elements are either metal or ceramic, and the process is known as joule heating. Heat is transferred to the air in the room by convection. A fan heater, also called a blower heater, is a heater that works by using a fan to pass air over a heat source. This heats up the air, which then leaves the heater, warming up the surrounding room. They can heat an enclosed space such as a room faster than a heater without fan, but, like any fan, create audible noise. An oil-filled radiator is a common form of convection heater used in domestic heating. Although filled with oil, it is electrically heated and does not involve burning any oil fuel; the oil is used as a heat reservoir, not as a fuel.
Tankless water heaters — also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters — are water heaters that instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. Copper heat exchangers are preferred in these units because of their high thermal conductivity and ease of fabrication.
Tankless heaters may be installed throughout a household at more than one point-of-use (POU), far from or without a central water heater, or larger centralized whole house models may still be used to provide all the hot water requirements for an entire house. The main advantages of tankless water heaters are a plentiful, practically limitless continuous flow of hot water (as compared to a limited flow of continuously heated hot water from conventional tank water heaters), and potential energy savings under some conditions due to the use of energy only when in use, and the elimination of standby energy losses since there is no hot water tank. The main disadvantage of these systems are their high initial costs.