The best available technology or best available techniques (BAT) is the technology approved by legislators or regulators for meeting output standards for a particular process, such as pollution abatement. Similar terms are best practicable means or best practicable environmental option. BAT is a moving target on practices, since developing societal values and advancing techniques may change what is currently regarded as "reasonably achievable", "best practicable" and "best available".
A literal understanding will connect it with a "spare no expense" doctrine which prescribes the acquisition of the best state of the art technology available, without regard for traditional cost-benefit analysis.[1] In practical use, the cost aspect is also taken into account.[2] See also discussions on the topic of the precautionary principle which, along with considerations of best available technologies and cost-benefit analyses, is also involved in discussions leading to formulation of environmental policies and regulations (or opposition to same).