Adam H. Cooke
Kilowatt? Watts? Kilowatt-Hours? What is the Difference?
Sometimes electricity can seem magical. Your house is powered by the power of wires. The lights turn on when you flip a switch, press a button, or the coffeemaker wakes up. How does it all work, you ask?
This article explains how electricity works. It covers everything from the watts required to power your lightbulbs to all the kilowatt hours of electrical energy that your utility records on each month's electric bill.
What's a Watt?
How electricity works with water
Measurement of power flow
Watts, Kilowatts and Kilowatt-hours
What electricity is like running a marathon
Get kWh and kW on your electric bill
How solar panel costs can be reduced
Your state's effect on the solar energy value
What is a Watt?
A watt (W), is one unit of electricity. A watt (W) is a unit of power. Technically, it's a measure of energy transfer equal to one joule per sec. However, since no one outside of a laboratory has ever used the term "joule", we'll keep it at "watt."
Power is voltage divided by amperage. One watt (W), equals one volt, V, and one ampere (A).
One way to look at electricity is as if it were water. Amperage refers to the flow and voltage is the pushing or pressure. Amperage can also be called current when discussing electricity.
Electricity is similar to water
Imagine a hose that has a spray nozzle at the end. The nozzle can be set to one of three settings: low, medium, or high. The water pressure behind a nozzle is constant. It is similar to voltage. The off position has no flow and therefore no power.
You'll have power if you turn the nozzle to "low". Now water is flowing because you have increased the amperage. The flow is measured by gallons per hour, which, to use our metaphor, would be called the "wattage".
To increase the amperage, turn the nozzle to high. This will give you more power and "wattage".
Measurement of the power flow
Let's keep the water metaphor going: The flow is a measure the power. After ten minutes, you can point the hose into a bucket and fill it up. The amount of water that flows into the bucket is a measure how much energy was passed through the hose.
The lightbulb is a common way that people interact with watts. A 100-watt lightbulb needs to produce enough power to glow. You've used 100 watt hours if you left a 100-watt bulb on for one hour.
One kilowatt (kW) equals 1,000 watts. If you have 10 100-watt bulbs (1,000 watts) on for one hour, that's one kWh.
This is why low-wattage light bulbs are so popular. A 14-watt LED bulb can produce as much light as 100-watt incandescent bulbs. It only requires 14 watts. This means that you can run 10 14-watt LEDs for 7.25hrs and consume the same amount as an incandescent bulb in one hour.
You can power with one kilowatt hour
5 100-watt incandescent bulbs For 2 hours
21 23-watt compact fluroescent bulbs For 2 hours
35 14-watt LED bulbs For 2 hours
Watts, Kilowatts, and Kilowatt-hours - Power vs. Energy
A watt is an indicator of power or the ability to work. A watt-hour, on the other hand, is an indicator of electricity. This is the amount of work performed over a given time period.
A kilowatt simply refers to a thousand watts. A kilowatt hour is an hourly record of an average output exceeding a thousand Watts.
A marathon runner is another way to look at power and energy. The ability to run at a given pace and the distance covered by a runner is an example of power.
The fastest marathoner in the world finished a race in just 2 hours in 2019. This means that he ran at about 13.1 miles an hour. The marathon distance of 26.2 miles is the measure of his energy.
The runner would have used 600 watt-hours of power over the course of the 26.2 mile race if his consistent power output was 300 WHT0_. His total energy output, if he ran at the same power output for five hours, would be 1,500 Watt-hours or 1.5 Kilowatt-hours.
Your electricity bill will be reduced by kW or kWh
A meter records how much electricity your home uses during the day. It spins or digitally counts up to show you the total power consumed at any given time. This adds up to a set number of kWh energy consumption at the end each month.
The company "reads" the meter at the end of each billing cycle and calculates the total energy consumption. The company then applies their complex calculations to bill you at cents per kWh.
If you use 1,000 kWh per monthly and your electric rate for $.15/kWh, your bill would be $150.00 plus any additional connections and service fees.
How solar panels can reduce your energy bills
Solar panels generate power that can be used to run your dishwasher and air conditioner. By replacing the electricity you would otherwise have to buy from the utility company, solar power can reduce your energy bills.
Solar panels create electricity when photons of sunlight excite electrons on one layer of the panel's surface. The excited electrons travel through conductive wires to reach the other side of the panel. The solar electricity can be diverted through the wires of your home to provide power.
Each panel is rated capable of converting a certain amount of photons into electrons under full sunlight--i.e. A certain amount of watts. A solar panel's peak power output is approximately 340 watts. For a typical solar system to work in a home, it will require 18 panels. The total output is about 6 kW.
Although a 6-kW solar panel system is capable of producing that much power in full sunlight, the sun's rays are only at their peak at midday. The sun shines at an angle that is lower during other times of the day.
Referring to the above discussion on voltage/amperage, once enough sunlight touches a solar panel's surface, its full voltage will be ready. However, the number of photons excited electrons is low so its amperage (current), is low.
The number of excited electrons rises as the sun shines brighter on the panel. It looks like a bell curve, with the lowest numbers occurring at sunset and sunrise and the highest at midday.
People who study solar have created peak sunlight hours to make it easier for people to see how much solar panels can produce during a typical day.
They take all of the solar energy available at a given location on the earth for a year and divide it by 360 to find the average amount of time the sun must shine from the highest point in the sky in order to produce that much energy.
Imagine that you live in an area where there are 5 peak hours of sunlight per day. On an average day, your 6-kW solar system can produce 30 kWh of electricity. Your system could produce about 30 kWh of electricity on an average day. However, it is more likely that your system will produce more or less energy each day. The annual production would be around 10,950 kWh (365 times 30/day).
Our example shows that a home with 12,000 kWh of electricity per year can get less power from the grid by using our 6-kW system and five peak sun hours per day. This is a $1,642.50 savings over the same time period thanks to solar.
Your state has an impact on the price of solar energy
Each solar kWh is not created equal. However, unless you have Net Metering they aren't all credited equally to the energy bill.
Net metering allows you to receive a full retail-rate credit for every kWh of solar energy produced. You earn credit if your solar panels produce more electricity than you use monthly. This credit can be applied to your next month's bill.
Find out more about What exactly is net metering?
While net metering is a common practice in most states, some states don't have them. Going solar isn't as financially beneficial if you don't have full retail credit for the electricity your solar panels produce.
To find out more about net metering, read our state solar guides. You can also use the most precise online calculator to calculate the cost and savings of solar panels for your roof.
The Key Takeaways
Watts and Kilowatts measure power or the ability of a person to do work.
Kilowatt-hours refer to energy or the work that is done over time.
Consuming power through appliances and devices can lead to increased energy consumption. This is measured and recorded in kilowatt hours on your electric bill.
Solar panels produce power. The sun's rays can create kilowatts of energy, which will reduce your electric bill.