Electricity 101

February 9, 2022

NOTL Hydro uses a lot of terminology in their public documents.  Many of these are electrical terms such as Amps, Volts and Watts.  In this blog I shall try to explain these terms.  This is an accountant explaining electrical terms so I will need to keep it as simple as possible so that I might understand it.  I did have it reviewed (and edited) by our Professional Engineer.


An Ampere (A) or Amp is the current that flows through an electrical circuit.  Electrical current is the flow of electrons through a conductor, like a copper wire, analogous to water flowing through a pipe.  It is named after André-Marie Ampère, a French mathematician and physicist.  The symbol for electric current is I, and represents how Ampere described the phenomenon of current flow as “Intensite” or “Intensity”; that descriptive name makes me think the physicist was shocked once or twice during his experiments!

A typical house in NOTL has a 200 Amp service so the amount of current flowing at any point of time cannot exceed 200 Amps.  This is plenty of capacity to run all your household appliances and more, but not enough if you have industrial equipment.  Then you might need a service upgrade to 400 Amps.  Talk to your electrician if you think you might need an upgrade.

Within your house your breaker box further restricts the amperage for the individual circuits running through-out your house.  These are typically 15 Amps for most circuits, and more for electric dryers and stoves.  If you trip a breaker, your equipment is trying to draw too much current which could be dangerous.

The amperage also determines the size of the wire needed to conduct electricity.  The higher the amperage then the bigger the wire needed. 


A Volt (V) is the force that pushes the current through the circuit.  It is named after Alessandro Volta, an Italian physicist known for inventing the battery.

The standard voltage for a house in Ontario and most of North America is 120V.  This standard voltage varies around the world.

The higher the voltage the easier it is to deliver large quantities of power.  With higher voltages you need less amperage to deliver the same amount of power.  This means that the wires do not have to be as big.  This is an important consideration when you have power lines that are many kilometers in length.  The transmission lines that deliver the power to NOTL are 115,000 volts.  Our lines that distribute the power around NOTL are 27,600 volts or 4,160 volts.


A Watt (W) is a unit of power.  It is named after James Watt, a Scottish inventor best known as the inventor of the steam engine.  James Watt’s steam engine’s capacity to do work was measured against his machine’s predecessor, the humble horse, and hence, the advent of the term “horsepower”.  There are 745.7 watts in one horsepower.  The watt is the amount of power needed to run an electrical device. A 60 W light bulb will consume 60 watts of power when turned on.  A kilowatt (kW) is a thousand watts, a megawatt (MW) is a million watts, a gigawatt (GW) is a billion watts and a terawatt (TW) is a trillion watts. 

When we report on watts it is usually the demand for power at a moment in time.  For instance, the peak demand for power in NOTL was 52.6 MW in July 2019.  The peak demand in Ontario was 27 GW in August 2006.  A typical house has a peak around 4 kW.  Our pad-mounted transformers (the green boxes for underground services) are usually 100 kW and serve 8-10 houses so have plenty of spare capacity. 

The amount of power that can be provided is determined by both the size of the service (Amps) and the pressure (Volts), calculated using Watt’s Law:  1 Watt = 1 Amp x 1 Volt.

Kilowatt-hour (KWh)

Our bills are calculated using kilowatt hours (KWh).  The KWh is a unit of measure for energy.  Electrical energy is the amount of power used over time, and a KWh is one thousand watts used in an hour, as measured by our meters.  A typical house uses around 800 kwh a month.  NOTL used 224 GWh last year and Ontario used 132.2 TWh in 2020.


As electricity moves through power lines and loads it encounters resistance; similar to friction.  Resistance is measured in Ohms (Ω) and is named after Georg Ohm, a German physicist.  The fundamental physical law that defines the relationship between voltage, current and resistance is known as Ohm’s Law, in his name.  Ohm’s Law states that one Ampere of current will flow through one Ohm of resistance when one Volt is applied to the circuit; mathematically represented as: 1A = 1V/1Ω

As NOTL Hydro moves electricity through town and to your location we lose some of the power due to this resistance.  Currently, our loss rate is an average 3.73% though this has been declining over time.  Our lines are made of copper or aluminum which are good conductors of electricity so have a low level of resistance.  If you look up at our lines you will see that the lines are held in place by insulators.  These are typically made of materials such as polymer or porcelain which have a very high level of resistance and so prevent the current from leaking away from the line.  Likewise, rubber has a high level of resistance so is often used to coat a line and make it safer to handle when worked on by our crews.


As we know, electricity can be lethal.  The lethal part of electricity is its amperage as that is the amount of current interacting with your body.  As little as 0.05 Amps can be lethal.  You will recall above that a typical breaker is 15 Amps.  This is 300 times the lethal level.  Regular household current can be lethal.  The reason it is usually not is due to voltage (volts) and resistance (ohms).  The typical household voltage is 120 volts.  The resistance of a human body can be as high as 100,000 Ω.  Using Ohm’s Law, the amount of current that would flow through the body if connected to 120 volts is:

120V/100,000 Ω = .0012A, well below the lethal level. 

At 120 volts, the amount of current that flows is limited by the natural resistance of the human body and we normally just feel that tingling feeling from making contact with the live circuit.

However, there are many factors that can reduce the natural resistance of the human body and thus make household electricity dangerous and even lethal.  These include if the body is wet, if the body is in contact with high conducting material such as water or metal, if the exposure to electricity is for an extended period of time or if there are electrical issues in our body (yes, our body has and generates electricity).  To ensure you are safe we recommend:

  • Turn off the power at the breaker before doing any work involving the electrical system in your house; this is mandatory as dictated by the Ontario Occupational Health and Safety Act.
  • Test for power with a voltage tester before commencing any work, and test the tester first to ensure it works properly.
  • Stay dry.
  • Wear rubber soled shoes or boots and rubber gloves if possible.
  • Use insulated ladders and tools.
  • Do not leave any live wires unattended.

Finally, our power lines are thousands of volts and this will overcome any resistance in your body.  Stay well away from any downed power lines.

For additional termsElectricity Terms – Niagara On The Lake Hydro Inc. (notlhydro.com)

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