Energy is often wasted due to heat loss and friction. It is possible to improve the efficiency of a device by reducing the amount of friction or energy lost as heat.
Reducing Friction
An engine without lubrication is inefficient. There is a lot of friction between the parts of the engine. Energy is wasted as heat and sound. Adding oil as a lubricant will improve the efficiency of the engine.
Reducing Heat loss
A hot water tank that is not insulated is inefficient. A lot of heat energy is lost from the tank to the surrounding air. The efficiency of the tank can be improved by covering it with a lagging jacket. This reduces the amount of heat energy lost.