Routine audits will have to be carried out every four years, with the first to take place within a year after a company has been introduced into the list of big energy consumers, to be compiled by the Central Statistics Bureau.
The amendments apply to companies with more than 249 employees, companies with a yearly turnover of at least €50m and the yearly balance of at least €43m, as well as companies that consume more than 500 Mwh of electricity within a year.
Authors of the amendments estimate about 1,000 companies will be affected.
If a company in the list doesn't act to improve its energy efficiency, it will have to pay an extra sum set by the state.
The amendments also require the introduction of a state energy efficiency plan.