This post picks up from the last one on Electricity Industry Cycle.
Up to about 1990, a single electricity Utility was responsible for generation, transmission, distribution, and retail services in most jurisdictions.
In order to minimize the delivered cost of electricity, the integrated Utility performed Integrated Resource Planning (IRP) which provided a high to medium level plan.
Integrated Resource Plan was usually filed with the Regulator or the Government which reviewed it for compliance with the requirements, in a public proceeding in some jurisdictions.
Some countries, states, or provinces still follow this general approach.
Integrated Resource Plan provides the optimal combination of capital investments, and operating and maintenance expenses in generation, transmission, distribution, and retail areas i.e. a portfolio, for a few credible scenarios. The following chart describes the IRP: