Increasing efficiency reduces unwanted transfers

1. Efficiency rises when a larger fraction of the same input reaches the intended useful store.
2. For a fixed input, $E_{total}=E_{useful}+E_{dissipated}$, so reducing dissipation increases useful output.

Reduce friction and resistance

1. Lubricating bearings and gears reduces friction, so less energy enters thermal stores and more reaches the kinetic output.
2. Ball bearings, smooth surfaces and aligned parts can reduce rubbing and deformation.
3. Lower-resistance conductors and secure electrical connections reduce unwanted heating by current.

Reduce drag and unwanted vibration

1. Streamlining reduces air resistance, so less energy is transferred to the thermal stores of the air and vehicle.
2. Reducing unnecessary vibration limits transfers as sound and heating.
3. A method improves efficiency only when it reduces an output that is unwanted for the device's intended purpose.

Insulation improves heating systems

1. Insulation around a hot-water tank reduces transfer to the surroundings, leaving more energy in the water's thermal store.
2. A lid reduces convection and evaporation, so less energy is required to heat the contents.
3. Loft insulation, cavity-wall insulation, double glazing and draught proofing reduce transfers from buildings.
4. Insulation is not always helpful because refrigerators and computers need controlled heat removal.

Improvements have limits

1. No real process reaches $100\%$ efficiency because some unwanted transfers are unavoidable.
2. An improvement may add mass, cost, maintenance or manufacturing impacts.
3. Extra insulation gives progressively smaller savings once transfer through that part is already low.

Judge changes from evidence

1. Compare devices under the same operating conditions and for the same useful task.
2. A measured efficiency increase should match a reduction in unwanted output or an increase in useful output.