Calcom Blog


January 28, 2014

When you buy electricity, you’re charged by the kilowatt-hour (kWh). If you use 1000 watts for 1 hour, that’s a kilowatt-hour. Utilities also charge commercial and ag users a Demand Charge, which is based on the flow of electricity used during the single highest 15 minute period of a month.

Let’s go over some commonly used terms and see how they relate to your electric bill(s) and our photovoltaic systems. Photo (light) + voltaic (electricity)electricity produced from light. Often called PV, to save time.

Volt: electrically, voltage is the measure of the potential to do work, like water pressure in a garden hose.

Ampère, or Amp: amperage is the flow of electricity, like water flowing through a hose. So, the monthly Demand Charge is based on the maximum amperage required over any one 15-minute period. In the water hose metaphor, demand is a measure of how much the nozzle is opened and consequently how big the hose has to be to maintain pressure (voltage).

Watt: a measure of electrical power that equals volts times amps. In a water hose, a small flow at high pressure could have the same power as a larger flow at lower pressure. So, 10 amps at 480 volts = 4800 watts. Likewise, 20 amps at 240 volts = 4800 watts.

Watt-hour: a measure of energy that equals watts times time. Using the water analogy, energy would roughly equate to the amount of water moved over a given time period. You could use 100 watts for 2 hours for 200 watt-hours, or 200 watts for 1 hour for 200 watt-hours.

We install PV systems to offset the kilowatt-hours or megawatt-hours you use. Kilo means one thousand and is abbreviated as kW. So, 1000 watts is 1kW. One million watts is a megawatt (MW). Many growers can now use Aggregated Net Metering (ANM offsets multiple meters with one PV system) to offset up to a MW of electric usage.

We typically offset the costs of 95% of your electric usage with a properly sized PV system. The actual PV system size will vary depending not only on the size of the motors you’re offsetting, but the amount you use them. We use advanced Ag rate forecasting to determine what, exactly, offers you the best ROI.