Efficacy vs. Efficiency — What's the Difference?

The ability to produce a desired effect.

Often involves optimizing processes and resource use.

Often used to evaluate the success of treatments or interventions.

Measures how well resources are used to achieve a goal.

Does not necessarily consider the resources used to achieve the effect.

Critical in operations management and economic theory.

Focuses on the effectiveness of an approach or solution.

Can apply to energy use, time management, and more.

Essential for proving that a concept or theory works in practice.

Achieving maximum productivity with minimum wasted effort or expense.

The ability to produce a desired or intended result

Efficiency is the (often measurable) ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without waste.

Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as effectiveness, and it has often been used synonymously, although in pharmacology a distinction is now often made between efficacy and effectiveness.The word efficacy is used in pharmacology and medicine to refer both to the maximum response achievable from a pharmaceutical drug in research settings, and to the capacity for sufficient therapeutic effect or beneficial change in clinical settings.

The quality or property of being efficient.

Power or capacity to produce a desired effect; effectiveness.

The degree to which this quality is exercised

Ability to produce a desired effect under ideal testing conditions.

The ratio of the effective or useful output to the total input in any system.

Degree of ability to produce a desired effect; effectiveness.

The ratio of the energy delivered by a machine to the energy supplied for its operation.

Power to produce effects; operation or energy of an agent or force; production of the effect intended; as, the efficacy of medicine in counteracting disease; the efficacy of prayer.

An efficiency apartment.

Capacity or power to produce a desired effect;

The extent to which time is well used for the intended task.

(dated) The quality of producing an effect or effects.

The extent to which a resource is used for the intended purpose; the ratio of useful work to energy expended.

(US) A one-room apartment.

The ratio of the output to the input of any system

Skillfulness in avoiding wasted time and effort;

Efficacy often refers to the potential for success under ideal conditions, while effectiveness is about success under real-world conditions.

Yes, by optimizing the use of resources, one can maintain or even enhance efficacy while improving efficiency.

Efficiency is defined as the optimal use of resources to achieve a goal or result with minimal waste.

Yes, a process can effectively achieve its goal (efficacious) but may do so using more resources than necessary, making it not efficient.

Yes, a method can use resources optimally (efficient) but may fail to achieve the desired outcome, making it not efficacious.

Efficiency is influenced by how well resources like time, money, and materials are utilized in the process of achieving a goal.

Efficacy refers to the ability to achieve a desired or intended outcome effectively.

Yes, technological advancements can streamline processes and reduce resource waste, thereby improving efficiency.

An example would be using LED lighting, which provides the same level of light as traditional bulbs but uses less energy.

Considering both ensures that a method not only achieves its intended results but does so in a resource-optimal manner.

In healthcare, efficacy is crucial for ensuring that treatments and interventions achieve their intended health outcomes.

Environmental considerations can lead to the adoption of sustainable practices that not only conserve resources but also reduce waste, thereby improving efficiency.

Efficacy is measured by the extent to which a specific goal or intended result is achieved.

Businesses can reduce costs, increase productivity, and enhance competitiveness by optimizing resource use.

Efficacy in educational programs is evaluated by assessing the achievement of educational goals and learning outcomes.