UNDERSTANDING ELECTRIC DEMAND 電力デマンドの理解のために Information to help you make cost-saving energy-use decisions.
Defining Our Terms
kW Rate of using electricity (Demand).
kWh Electrical energy actually used (Energy).
A measure of energy use equal to the ratio of total kilowatt-hours used in a given time period divided by the peak kilowatt use during that time, multiplied by the hours in the time period.
Load factor expresses how well or poorly a given electric system is being utilized. Electricity users strive for a better load factor, or the most efficient usage of their installed electric equipment. The closer to 1 a given load factor, the better is the system's efficiency.
The rock crusher who has high electric demand for small periods of time and is not a big overall electricity user usually will have a very low, or poor, load factor. The energy-efficient process line, which takes advantage of electrotechnologies and state-of-the-art controls, will likely have a much better load factor.
While often used to measure monthly billing cycles, a load factor's time variable can be any desired length.
What Is This Thing Called Demand?
This is not the case among commercial and industrial energy users, whose electricity use-both consumption and demand-varies greatly. Some need large amounts of electricity once in a while-others, almost constantly. Complicating this variable usage and demand is the fact that electricity cannot be stored. It must be generated and supplied to each customer as it is called for-instantly, day or night, in extremely variable quantities. Meeting these customers needs requires keeping a vast array of expensive equipment-transformers, wires, substations and even generating stations-on constant standby. The amount and size of this equipment must be large enough to meet peak consumption periods, i.e., when the need for electricity is highest.
Utilities and public service commissions around the country have determined that the most equitable way to cover the cost of this equipment is to have those customers who create this demand and the need for power during these peaks pay for its availability. For this reason, utilities spread the costs of this extra equipment among all commercial and industrial customers as a separate charge for demand.
Defining Demand Customers
Comparing Demand and Consumption
But what about your demand charge? At an average cost of $8.32 per kW and the meter reading at 15 kW (8.32 x 15), the demand charge would be $124.80* (for customers in Service Classification No. 2, Small General Service-Demand).
The prices in this example became effective February 12, 1999 and exclude applicable surcharges and taxes.
Niagara Mohawk customers billed on the demand price who provide the transformers required to take service, as designated by Niagara Mohawk, have their charges reduced by $ .90 per kW billed.
Understanding Demand Metering
A demand meter's needle advances as electricity consumption increases, just as your speedometer needle advances as your speed increases in a car. When you stop the car, the needle moves back to zero, regardless of the highest miles per hour reached on the trip. Unlike a speedometer needle, demand meters record the highest average kilowatts reached and maintained in a 15-minute interval within the billing period.
If within one billing cycle your usage reaches 50 kW, for example, and stays there for 15 minutes, the meter needle remains at 50 kW unless or until your usage exceeds that level. If your usage later reaches 55 kW and stays there for 15 minutes, the needle will then stay at 55. The new index point is maintained, even when you are using electricity at below 55 kW, until the meter reader comes to record the demand and resets the meter back to zero.
For example, suppose you have a 10 kW motor in one part of the building and a 15 kW motor in another. If you operate both units simultaneously, the demand meter will record 25 kW. However, if you can use the motors alternately, operating the 10 kW unit only when the 15 kW unit is off, the maximum demand reading will be only 15 kW. The 10 kW saved would save about $82 per month, or $984 per year.
Some intermittently used equipment can be operated using various interlocks and automatic controlling devices. Since each kW demand saved is worth $8.32 per month (at current demand prices), looking into these types of devices makes good sense.
Saving Energy with Demand Control
The Demand "Ratchet" Clause（デマンド料金制度はラチェット条項を前提にしている）