Economies of scale occur when firms achieve per unit cost savings by producing more of a good or service (that is, when average costs decrease as output increases). Such effects arise when it is possible to spread fixed costs over a higher output. Examples of scale economies are the bigger lorry that transports more while still requir- ing only one driver or the larger plant that does not require more spare parts to be kept in stock than the smaller plant.
Source: Glossary of terms used in EU competition policy, Antitrust and control of concentrations, European Commission, 2002