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Understanding Home Energy Use: kW Vs. kWh


When people start researching solar power for their home, they often need to understand kWh versus kW – kilowatt-hours versus kilowatts. Put simply, a kWh is a measure of energy used over time, while kW is a measure of power. Let’s take a deeper look at what this means for homeowners, especially those considering a solar energy system to keep their energy costs in check.

Understanding Your Energy Use

From your air conditioner to your electric toothbrush, your home’s electrical appliances use power. Typically, electrical power output is measured in watts. Sometimes, though, energy use is so high that you need a higher unit of measurement. That’s where kilowatts and kilowatt-hours come in.

What Is A Kilowatt?

A kilowatt is a unit of power equaling 1,000 watts. For example, a dishwasher might be rated at 1,200 watts, which you can also express as 1.2 kilowatts (kW). A home air conditioner might have a peak power rating of 4,000 watts, or 4 kW. Meanwhile, a more powerful electric car’s motor might be rated for 115 kW of power.

What Is A Kilowatt-Hour?

A kilowatt-hour (kWh) is a measurement of how much energy a device expends in one hour. Consider how many watts a TV uses: A 50-inch LED TV, for example, might use 80 watts of electricity. Watching it for 3 hours per day uses 240 watt-hours, or .240 kWh. Over the course of a year, that’s about 87.6 kWh.

If you have an electric car that requires 40 kWh of charging each week, that’s 2,080 kWh in a year.

What a kilowatt-hour of electricity can do depends on the power a device requires. An electric car might be able to drive 3.5 miles on 1 kWh, while that same amount might power your refrigerator for an hour.

The Average Use And Cost Of Kilowatt-Hours In The US

According to the U.S. Energy Information Administration, the average electrical consumption per household is 893 kWh per month. That’s just under 30 kWh per day, 5% - 10% of which might be phantom load.

The national average cost per kWh for homeowners in 2021 was 13.72 cents. This was a 4.3% increase from the previous year, which was the fastest average increase since 2008. Rising energy costs along with increasing energy consumption might be factors in why the rate of homeowners going solar is also rising.

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How Many kWh Do Solar Panels Generate?

Solar panel systems, also called photovoltaic (PV) arrays, can be built in various sizes to suit different homes. For example, larger homes or homes with lower sun number scores may need larger PV arrays to meet their needs.

Based on the average national home energy use, the average home would need a 6.62-kW solar system. That’s enough to produce about 9,000 kilowatt-hours, or 9 megawatt-hours (mWh) of energy in one year – nearly enough to cover the average grid-tied home’s yearly need. The rest would come from the utility company’s power sources.

How Much Can Solar Panels Save Homeowners On Utility Bills?

Utility companies typically set their prices per kWh, along with establishing policies specific to customers who produce renewable energy. Some companies use net metering, a billing system that credits homeowners for the energy they produce. This is balanced against energy they might have to take from the grid at night or on cloudy days. Typically, net metering results in lower energy bills. Some utility companies may also have rate plans that save solar homeowners money by charging a lower price per kWh.

How much solar panels can save you on monthly electricity bills depends on your electricity provider’s policies and rates, your home’s energy efficiency, the amount of electricity your solar system would produce and other factors.

Understanding Your Utility Bills

Your electric bill may list the total energy you used in a month, along with the electricity rate per kWh. The rates might vary by time of day if your utility company has Time Of Use or peak demand rate plans.

Taking a careful look at your utility plans will help you understand the kWh of electricity your home uses throughout the year. This information can help you use less energy and decide how many solar panels you might need.

How To Reduce The Amount Of Energy Your Home Uses

There are many ways to cut household energy consumption. Switching from incandescent to LED bulbs in light fixtures is a low-cost way to cut energy use. Some homeowners also reduce electricity usage by sealing their air conditioning ducts, updating their insulation and upgrading to ENERGY STAR®-certified appliances.

The Bottom Line: kW Measures Power, kWh Measures Energy

Now that you understand the differences between kW and kWh, you can find ways to reduce the number of kilowatt-hours you use. This can be as simple as ensuring you don’t run a load of laundry during peak hours or switching to energy-efficient appliances. You can also consider how solar power might help lower the costs to power your home.

Ready to use the latest solar technology to save on your utility bills? Let’s get started!

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Considering solar? Run the numbers to see if it all adds up for you.

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