Explaining watts, kilowatts, and kilowatt-hours (kW vs kWh)

From the watts required to power your lightbulbs to the kilowatt-hours of electrical energy utilized that your utility records on your monthly electric bill, the article below explains how electricity works.

What is a watt?

A unit of power is a watt (W). Consider power as “the capacity to perform work.” Technically, a watt is a unit of energy transmission that is equal to one joule per second, but because “joule” hasn’t been used outside of a lab since physics class in high school, we’ll stay with “watt.”

Voltage times amperage equal power in an electrical system. Alternatively, one volt times one amp is equal to one watt (W) (A).

The analogy between electricity and water is a useful one. Amperage is the flow, whereas voltage is the pushing, or pressure. Current is another name for amperage when referring to electricity.

How electricity is like water

Think of a hose that has a spray tip on the end. If the nozzle has three settings—off, low, and high—what would they be? The water pressure behind the nozzle is constant; that pressure is like electricity. No flow means no electricity while the switch is in the off position.

You have power if you set the nozzle to “low.” Water is flowing now that the amperage has been increased. In keeping with our metaphor, the flow is expressed in gallons per minute and corresponds to the “wattage”.

You can get additional power—more “wattage”—by turning the nozzle’s high setting in order to raise the amperage once again.

Measuring the flow of power 

Continuing the water analogy, the power is indicated by the flow that is emanating. You may fill a bucket by directing water into it for ten minutes. A measure of the energy that flowed through the hose would be like the water that poured into the bucket.

The lightbulb is a common method that individuals engage with watts. Let’s say that a 100-watt light bulb requires that much energy to operate. 100 watt-hours are consumed if a 100-watt bulb is left on for one hour.

One kilowatt-hour (kWh) is equal to 1,000 watts, therefore if you keep 10 100-watt bulbs on for an hour (a kW of bulbs), you will have consumed one kW. (kWh).

This is one of the main factors contributing to the significant impact of switching to low-wattage light bulbs. A 14-watt LED bulb may produce as much light as a 100-watt incandescent bulb. As a result, 10 14-watt LEDs can be used for 7.25 hours while using the same amount of total energy as an hour’s worth of incandescent lighting.

You can power: using one kilowatt-hour.

Watts, kilowatts and kilowatt-hours: power vs. energy

Once more, a watt measures power, or the capacity to do work, and a watt-hour measures energy, or the quantity of work completed over a predetermined amount of time.

A kilowatt is just 1,000 watts, while a kilowatt-hour is a measurement of the average production of 1,000 watts over the course of an hour.

The image of a marathon runner is another way to visualize power and energy. Power is comparable to the capacity to run at a particular pace; the amount of energy expended depends on the distance covered.

The world’s fastest marathoner finished a race in 2019 in almost exactly 2 hours. That indicates that he expended enough energy to run for 26.2 miles in the marathon, which is the equivalent of around 13.1 miles per hour.

Over the course of the 26.2 miles of the marathon, the runner would have used up 600 watt-hours if we estimated his average power production to be around 300 watts. His total energy output would be 1,500 watt-hours, or 1.5 kilowatt-hours, if he could operate at the same power output for 5 hours.

kW and kWh on your electricity bill

A meter spins (or digitally counts up) as your home utilizes electricity during the day to keep track of how much you use overall. At the end of the month, the sum of these measurements equals a specific number of kWh of energy usage.

The business “reads” your meter and keeps track of the total amount of energy used at the conclusion of each billing cycle. They then apply their sophisticated (and occasionally incredibly difficult) calculations and charge you at a specific cents per kWh rate.

If you consume 1,000 kWh per month at a $.15/kWh rate, your bill would be $150.00 in addition to any additional connection and service fees.

How solar panels reduce your energy costs

Your dishwasher, air conditioner, and other gadgets can all be powered by solar panels. By substituting solar energy for the electricity you would have otherwise purchased from the utility company, solar energy lowers your energy costs.

Solar panels produce electricity when photons of light stimulate electrons in a single layer of the surface. The other layer of the panel attracts the excited electrons, which then move through a conductive wire to reach the other side. Solar electricity can be used to power your home by directing that energy away from the cables in your building.

Each solar panel is designed to produce a specific number of watts, or photons to electrons, under full sun. These days, a solar panel can produce a peak power of roughly 340 watts on average. For a total rated output of roughly 6 kW of power, an average solar system for a dwelling requires about 18 of those panels.

We are aware that a 6-kW solar panel system is capable of generating that much power in full sun, however although though the sun rises and sets all day, it is only considered to be “full” during midday. The sun is at a lower angle at different times of the day.

Returning to the voltage/amperage concept from earlier, a solar panel’s full voltage is ready as soon as enough sunlight hits its surface, but because there aren’t many photons stimulating electrons, the amperage (current) isn’t as high.

As the sun rises and shines more directly on the panel, the number of excited electrons grows up to the maximum, or full sun. When you examine solar energy output during the day, it resembles a bell curve with a rounded peak in the middle and lowest numbers at sunrise and dusk.

Peak sun hours were developed by those who study solar energy in order to make it simpler to comprehend how much electricity a solar panel can produce over the course of a typical day.

They calculate the average number of hours the sun would have to shine from its highest point in the sky to produce that much energy by taking the total solar energy produced at a certain location on Earth over the course of a full year and dividing it by 365.

Say you reside in a region with five on average during the peak of the day. On a typical day, your 6-kW solar system should provide roughly 30 kWh of electricity. Since most days aren’t typical, your system’s production is more likely to produce more or less energy on any given day, but would still total about 10,950 kWh annually (365 divided by 30 kWh/day).

With our example 6-kW system and 5 peak sun hours each day, a home that consumes 12,000 kWh annually can cut the amount of electricity they receive from the grid to just 1,050 kWh. That indicates a $1,642.50 savings due to solar throughout that time frame.

How your state affects the value of solar energy

Although each solar kWh is equal, not all of them are credited to your energy account equally unless you have net metering.

A law known as net metering makes sure that every kWh of solar energy is fully credited at the retail rate on your account. You receive a credit that is added to your bill the following month if your solar panels generate more electricity than you use in a given month.

However, some states do not have net metering regulations in force. Going solar is less profitable if you don’t receive full retail credit for the energy your solar panels produce.

Use the most accurate online solar panel calculator to evaluate anticipated costs and savings for solar panels on your individual roof. Read our state solar guides for information on net metering.