When you get your electricity bill, there’s a good chance you look at the total cost before anything else. Your electricity is billed by the kilowatt hour (kWh), but what does that even mean, and how is it different from a kilowatt (kW)? Let’s break it down.

A kilowatt is a unit (equal to 1000 watts) that represents the rate at which power is consumed, while a kilowatt hour is power used over a period of time, usually over a billing period.

You might be familiar with watts from the energy output of your household lightbulbs. Let’s see how operating one of these lightbulbs might translate to kilowatts and kilowatt hours.

Let’s say you operate one 100-watt lightbulb for 10 hours:

  • Energy Demand = 100 watts / 1000 (in a kilowatt) = 0.1 kiloWatt of Demand
  • Energy Used = 100 watts x 10 hours = 1000 watt-hours / 1000 = 1 kWh of energy consumed

Let’s say you operate six 100-watt light bulbs for 2 hour

  • Energy Demand = 6 x 100 watts = 600 watts / 1000 (in a kilowatt) = 0.6 kW Demand
  • Energy Used = 6 x 100 watts x 2 hrs = 1200 watt-hours / 1000 = 1.2 kWh of energy consumed

Here’s another example:

As you can see, operating one 60-watt bulb for 10 hours or operating six 100-watt bulbs for an hour is equal in terms of kilowatt hours, and will cost you the same on your energy bill. However, they are not the same in terms of energy demand – the single lightbulb uses energy at a lower rate than multiple, higher-wattage bulbs.

As this relates to your home and solar, lets say your home is drawing 1000 watts of demand and your solar system is producing 2000 watts.  If we take this scenario for 10 hours:

  • Energy Demand = 1000 watts / 1000 (in a kilowatt)  = 1.0  kW Demand
  • Energy Used      = 1000 watts  x 10 hours = 10,000 watt-hours / 1000 = 10.0 kWh of energy consumed

Your solar photovoltaic system is producing:

  • Energy                  = 2000 watts  / 1000  (in a kilowatt) = 2.0 kW instantaneous production
  • Energy Produced = 2000 watts x 10 hrs = 20,000 watt-hours / 1000 = 20.0 kWh of energy produced

10 kWh of solar production powered your house to meet the demand and 10 extra kWh of solar production went back to the grid, but thanks to net metering you get credit for all the energy and can take it back whenever your home needs it.

At ARE Solar, we build custom solar systems to fit each home’s unique energy demands and consumption. We’ll do the hard work of figuring out how many solar panels your home needs. Knowing your past consumption history, we can determine how to build the most efficient system that allows the sun to meet your consumption needs. Contact us for a free estimate or more information here.