The goal is to meet the expected long-term growth of demand with minimal cost, using a wide selection of means, from supply-side (increasing production and/or purchasing the supply) to demand-side (reducing the consumption).
[1] For example, for an electric utility the US law defines IRP as a planning process that evaluates the full range of alternatives, including new generating capacity, power purchases, energy conservation and efficiency, cogeneration and district heating and cooling applications.
[2] The methodology requires the utility to be able to influence all aspects of the supply chain from production to consumption, so in the US it is used by many vertically integrated (non-deregulated) ones.
However, the benefits of its consumption cannot be measured directly in kilowatt-hours; electricity is converted into other services, so improvements of the efficiency of the industrial equipment, lighting, air conditioning, household appliances can be potentially a more cost-efficient way to accommodate growth.
[8] In the perfect electricity market IRP is not needed: the demand-side would adjust on its own by the cost-reduction on the consumer size.