Many utility tariffs do not have a specified time window where the demand is measured. Under these tariffs, the facility could set their peak demand at any hour of the day. If the facility does not pay a demand charge, but only an energy charge, then there would be no reason to manage the demand or add an engine-driven generator. In general, if the utility's tariff has no demand charge and only an energy charge, then there is more incentive to install a wind turbine. If the utility has a high demand charge and low energy charge, then adding a wind turbine is probably not economical.
Wind turbines are good energy producers, but poor demand reducers.
The Lac Qui Parle School in Minnesota has a wind turbine and engine-driven generator. A 275 kW wind turbine was added along with an engine-driven generator to manage the school's peak demand, which was measured during a specified period of time. When the net load of the school less the wind turbine's output was above a target demand level during the demand measurement period, the engine-driven generator was run to reduce the demand below the target level. Due to the lack of significant financial incentives, this demand reduction scheme is not currently being used. Figure 26 shows the school and wind turbine.