Power system planning is the recurring process of studying and determining what facilities and procedures should be provided to satisfy and promote appropriate future demands for electricity. Plans should achieve the objectives of the entity doing the planning, including minimizing risk. The planning problem is to identify and choose among options, in the presence of uncertainties, so as to maximize or minimize the attributes. Planning and operating criteria have a dual nature: they are both attributes and options. Demand-side planning often is tied to generation planning because it affects the power and energy that the power plants will need to provide. High-risk, low-probability events usually are not considered by standard planning practices. Deciding on the planning objectives and the attributes for a given study is an important initial step in power system planning. Least-cost planning is known as integrated resource planning or integrated demand/supply planning.