What's a Kilowatt?

Always good to know how you're being charged.

by Alex Kelleher
5 min read - Published on 05/10/2022

When you switch to solar, you’ll start to see the value in acronyms like kW (kilowatt) or kWh (kilowatt-hours). Unlike Ms. Brown's 9th grade science exams, life is an open-book test. Don’t stress, we'll make it much easier to understand than your teenager’s ever-growing list of nonsensical abbreviations. Let's get you a foundational understanding of how the power you consume is measured so you can make informed decisions about your residential solar system.

What Are Kilowatts and Kilowatt-Hours

It's often difficult to appreciate the true value of a residential solar system without first understanding your power bill and how your custom solar system can make it obsolete. Interpreting your power consumption is not rocket science; if you can tell the difference between kW and kWh, you can decode the entire puzzle.

A kW is a unit of power that tells us the rate at which energy is consumed. For instance, some larger appliances, such as a 12,000 BTU air conditioner or a portable heater, take a flow of approximately 1.5 kilowatts to keep running.

Since the appliance companies know most of us will never bother to try and understand this, the wattage of most appliances is stamped somewhere on the back of the appliance or buried in some forgotten, dusty manual next to the broken headphones for your long-lost Sony Discman.

The kW number tells how much power that appliance uses, but these specifications are given in watts rather than kilowatts so you will need to convert the watts to kilowatts by dividing the wattage by one thousand.

The Numbers

Some common household appliance's power consumption:
Air Conditioner 1,500 watts (1.50 kW)
Refrigerator 450 watts (0.45 kW)
Personal Computer 365 watts (0.365 kW)
Oven 1500 watts (1.5 kW)
Ceiling Fan 80 watts (0.08 kW)
Lighting (Fluorescent) 40 watts (0.04 kW)
Vacuum Cleaner 1560 watts (1.56 kW)

Kilowatt-hours tell us the amount of energy consumed by an appliance if it is left running for one hour. For example, a 1500-watt appliance running for one hour will consume 1500 watts per hour or 1.5 kWh.

Let's calculate the kWh of your typical air conditioner to get an idea of how much energy is used over a month.
The wattage of an air conditioner = 1500 watts or 1.5 kWh
Estimated hours used per month = 200
Estimated monthly consumption = 1.5kWh x 200 = 300 kWh

The above numbers tell us that a 12,000 BTU (standard 1-ton air conditioner) will consume 300 kWh monthly if it runs for 200 hours. Assuming that the electricity rate is a constant 10 cents per kWh, your monthly bill to keep your home nice and cool will be 300 kWh x $0.10 = $30 per month.

Psst! Unless you have solar, it is extremely rare to see flat rate charges. Learn more about how your power is priced here: How Much Does Your Energy Cost

Why Are These Metrics Important?

Understanding the math behind powering your toaster, pool pump, or pumpkin spice-scented Glade Plug-in can give you important insight into your energy needs when it comes time to start your custom solar design.

For instance, your calculator will probably tell you running an air conditioner all day is expensive because it consumes 1.5kWh of power. In contrast, running your A/C less and adding a ceiling fan could cut costs significantly, because the fan only consumes only 0.08 kW compared to the high energy consumption of an A/C unit cranking non-stop.

Here are the main points to remember:

  • The higher the wattage, the greater the energy consumption.
  • The duration of energy consumption also plays an important part in determining the overall cost.
  • To save on residential solar energy costs, it's better to restrict the energy consumption of larger appliances that run continuously for longer periods. 

How Does This Information Apply to a Solar Owner?
Knowing your average energy usage will help you determine how many solar panels you need for your house.
An average US household consumed about 900 kWh per month in 2021—that is about 20 solar panels, give or take.

While this is just a ballpark estimate, it should give you a rough idea of how many panels are needed for an output of around 900 kWh per month. Take a peek at your power bill and see how you measure up!

How Does the Utility Company Measure Consumption?

Utility companies install a meter outside of the house where the power line enters the property that provides energy usage stats in an easy-to-read format.

Back when DVDs were still rented by mail, a meter reader would come to your house and take the reading from the analog meter. With advances in technology, automated electricity meters automatically send your usage data to the utility company at regular intervals.

Smart meters are becoming more and more common in most states. Some meters let you receive readings on your mobile phone along with other useful statistics that can help you keep track of your energy usage, and net-metering details—that's where the utility company pays you for your extra power you're sending back to the grid.

Energy prices have been constantly on the rise. To keep the antiquated power grid from complete and utter failure planned "Brown Outs" or rolling outages are becoming more common by the day. It's time to take control of your energy future. Give us a call and let us help you create your own personal power.