Efficiency is a really important consideration to an engineer. This is whether a civil engineer is thinking how efficiently a building can be heated, an automotive engineer trying to make sure his engine is as efficient as possible or an electrical engineer is thinking how efficiently a kettle might use electricity.
As a design engineer working on medical devices that are a lot smaller and less powerful than those examples I have to be efficient about other things. The regenerative medicine drugs, that the devices I design can deliver, can cost £300 – £30,000 per patient!! So what I have to do is make sure the drugs are delivered as efficiently (as close to 100%) as possible as the NHS cannot afford to waste any of these very expensive drugs.