Power is used to drive devices, typically replacing or improving tasks normally done by dwarves, such as pumping water using a screw pump or milling certain types of food at a millstone. Power is produced by windmills and water wheels.
 Power requirements
- Axle: (1) per tile (horizontal axles and vertical axles both)
- Gear assembly: (5)
- Millstone: (10)
- screw pump: (10)
- Roller: (2) per roller
 Power transfer
Power can be transferred between devices using gear assemblies and axles. Axles transfer power in a single direction -- north, south, east, west, up, or down. Axles are classified as "horizontal" or "vertical", with the former going north/south or east/west, and with the latter going up or down Z-levels. Axles must terminate at a device, or a gear assembly, or another axle of the same kind. You cannot transfer power from a horizontal to a vertical axle (or from a north/south to an east/west horizontal axle) without a gear assembly. Horizontal axles may be built individually up to 10 tiles long; if you want a longer axle, you may simply build two or more of them in a line; you don't need gear assemblies between them. Vertical axles are always placed one tile at a time, and may be as tall as you wish.
Gear assemblies take up a single tile and transfer power to any device, axle or gear assembly within the six orthogonally adjacent tiles (north, south, east, west, above, below). Gear assemblies are best used for moving power through right-angles. For example, they can be built as bases for windmills to move power out sideways along an axle. Gear assemblies can also be linked to a lever to disengage them, which will stop power transfer through that tile. Don't do this with gears that are supporting machinery above them, as the machinery may collapse.
Because of the high power use of gear assemblies (5), axles are more appropriate and convenient to build when transferring power across horizontal or vertical distances. An axle uses (1) power for every tile of power transfer. An axle 5 tiles long will use (5) power. Axles can be directly attached to windmills, waterwheels and screw pumps in order to provide power. For security, one can make an axle-train cross a moat by first going down the moat, across, and then up. Or perhaps a screw pump will make a floor-type security-wall for a downward axle.
Devices that use power are also capable of transferring it. Adjacent screw pumps will transfer power between themselves. The only way to prevent this is to leave a tile gap between devices, or move them diagonally from each other.
 Frozen Components
Machine components on ice will freeze solid. This also causes all connected components to stop working. When you look at a component using 'q', you can see if the component is "frozen" (not working because it is frozen solid) or "frozen elsewhere" (not working because another component is frozen solid).