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120V vs 240V Power Differences - Nature's Generator

120V vs 240V Power Differences

Everything people should know about their home’s electricity and how to right-size systems to give solar power to the people.

This blog will examine 120-volt versus 240-volt power and explain why they’re different and when it is best to use one voltage over the other. We will also show load capacity calculations to right-size a home’s solar powered generator system to harness the free energy of the sun and protect your family when unexpected blackouts occur. With this information you can join millions of people transitioning to home solar-powered generator systems to help fight climate change.

So, let’s begin.

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You’ve lived with 120-volt and 240-volt outlets in your home your whole life, but have you ever thought about what makes them different?

Reverting to basics, you can easily distinguish a 120-volt outlet from a 240-volt outlet because the two types of outlets look completely different.

  • A standard 120-volt outlet looks like the outlet that you may have your bedside lamp plugged into.
  • A 240-volt outlet looks like the outlet you use for your electric stove or electric clothes dryer. (These outlets have receptacles for 3 or 4 prongs, depending on the specific need and appliance plug configuration.)

To understand the difference between 120-volt and 240-volt power we must review some basic facts about electricity -- like what it is, how it works, what makes it flow, and what type of electricity is used in our U.S. homes.

What makes electricity flow?

Electricity is the flow of electrons. The electrical wiring in your home acts as an electrical conductor and electricity “flows” through this wire. To understand how it flows we will take a brief microscopic dive into the process. The electrical wire is made up of atoms, each atom has electrons orbiting its nucleus. When you add new electrons to the wire, they move to join the existing atoms where each atom takes a new electron in its outer most shell (or orbit) and spits out an electron to the next atom and so on. This creates an electron flow -- which is the flow of electricity.

Now that you have this mental picture of electrical current as it moves through one of your home’s electrical circuits you can also understand that the more quickly the individual electrons flow through the electrical wiring, the more power this flow will provide to your home’s electrical outlet.

So, why do we need both 120V and 240V outlets in our homes?

Both the 120V and 240V outlets in your home are needed because which type of outlet you use depends on the power requirements of the electronic device or appliance being powered.

The 120 and 240 voltage outlets each provide a different amount of power. The 240V outlet basically is supplying twice the amount of power that the 120V outlet can. Additionally, different gauge electrical wiring is needed to transport the voltage. The 120V can use thinner gauge electrical wire whereas the higher voltage of a 240V outlet requires heavier gauge wire. If the wiring is not the correct gauge for the higher voltage -- the wire can overheat and become a fire hazard.

When to use your 120V outlets.

Your typical common appliances or devices like your refrigerator, dishwasher, microwave, computer, vacuum, lamps, cell phone (or other device) chargers all function well using a 120V outlet. Because so many of our household items only require a 120V outlet they are the most prolific outlets your home has – they are literally every 12 linear feet in your home’s wiring plan for your convenience.

When to use your 240V outlets.

In our U.S homes we also have some more power-hungry appliances that require more than 120 volts of power to run reliably.  Electric clothes dryers, water heaters, oven/ranges are some common examples of power-heavy electric appliances that might technically function on 120-volt current but won’t operate as effectively.

People also are often not aware that electrical appliances with motors require, when they first start up, a two or three second pull of more electrical power than they require for their running power. (The manufacturer’s face plate data lists only the device’s running power -- not its starting power requirements.) Why this is important is that with larger electric motors, 240V power circuits are preferred because fewer amps are required on start up.

U.S. historical electricity choice

Let’s take a short stroll in the annals of the history surrounding the development of electricity here in the US. There is still a lot of confusion in people’s minds about the difference between 110/220-volt electricity and 120/240-volt electricity, so it is probably important to spend some time to clear up that confusion.

What’s the difference between 110V verses 120V electricity?

Will you believe me if I answer: “Nothing.”?

Let me explain. We have Thomas Edison to thank for the first 110V direct current three-wire electric distribution system. We must credit Nikola Tesla for promoting alternating current over direct current here in the U.S. And finally, we must tip our hats to both Nikola Tesla and George Westinghouse for setting the 60 Hz precedent for our current US electric system.

Here’s a more detailed review of the history that brought us here

After inventing his incandescent light bulb in 1879, Edison established the Edison Illuminating Company in 1880. The utility distributed 110-volt direct current to some New York City customers. The 110 volts was important to

Edison because it was the perfect amount of power for his incandescent light bulbs.

In 1883 Edison, a direct current advocate, patented a three-wire distribution system that used two 110V conductors with a neutral conductor to create a 220V direct current electricity system -- which the rival alternating current proponent, Nikola Tesla later adopted to provide 110-volt power to incandescent lighting as well as 220-volt power to major appliances.

So, the “War of Currents” raged in the mid 1880’s with Edison backing 110/220V direct current power and his main competitor Nikola Tesla promoting the safety of the three-phase alternating current electric power. Tesla creates the Tesla Electric Light and Manufacturing Company in 1885 and then, that failing, the Tesla Electric Company in 1887

How 60 Hz became the US electricity standard frequency

Into the historical mix we must also add George Westinghouse (of electrical appliance fame) of the Westinghouse Electric & Manufacturing Company who hired Tesla to work for him as a consultant. While working with Westinghouse Manufacturing, Tesla and company engineers agreed on a current of 60 Hz current which set the precedent for the 60 Hz standard we still have today.

So, Westinghouse Electric is responsible for the standardizing of the 60Hz lower frequency which permitted both lighting and induction motors to run on the same frequency, although 50 Hz (that Europe and other countries use) could also run both, Westinghouse felt that existing U.S. arc lighting equipment performed better on 60 Hz frequency. Westinghouse Manufacturing felt that using the 60 Hz frequency the arc lighting did not produce a noticeable flicker -- and therefore selected 60 Hz instead of 50.

How the US realized that voltages needed to be standardized.

Back at the end of the 19th Century more and more electrical appliances came to the market and it became necessary to try to standardize the wide

range of voltages. As more homes and businesses started using electrical power, electrical suppliers knew standardization would be needed so that any US homes could run any US appliance.

Okay, back to the difference between 110Vand 120V...

The difference between these two voltages is so little that it is almost imperceptible to the end-user or the end-user’s appliances. So, what eventually happened is that over the years voltage gradually increased from 110V to 112V, 115V, 117V and finally to the current standard of 120/240V at 60 Hz around 1967. Therefore, today in the U.S. it is accepted that the 120-volt electrical service can be plus or minus 10 percent.

So, when I asked above if you would believe me if I said the answer to what’s the difference between 110V verse 120V is “Nothing” -- this is what I meant. In the US utility companies deliver electrical service to our homes at 120 volts plus or minus a ten percent variance. US appliances are designed to handle these variances so for all practical purposes, there is no difference.

This is the history explaining why U.S. households run on 60 Hz frequency 120/240-volt alternating current (AC) electricity, while Europe and other parts of the world function on 50 Hz direct current (DC) electrical power.

Another small aside, there was a time a bit later here in the U.S. that people wanted to switch our domestic electric infrastructure to direct current power, but because of the staggering cost associated with changing out the existing alternating current infrastructure, U.S. homes still operate on alternating current electricity.

So, US households use alternating current (AC) electricity

With alternating current, the flow of the charge changes direction periodically, hence the name “alternating current.” (Direct current always flows the same direction, hence “direct current.”) It’s important to note that your lamp (or whatever) will turn on whichever way the alternating current charge is flowing.

Also, it is interesting to note that utility companies use higher voltages for longer transmissions to reduce energy loss (think of the high-powered electrical lines held aloft by tall metal structures that you see running across the landscape when you’re on a long drive). After transmission, the utility companies then reduce these higher voltages down to 120/240V for safety purposes for home distribution.

120V vs. 240V – the one used will depend on your device’s power demand.

As we have established, U.S. homes have long been constructed to have both 120-volt outlets as well as 240-volt outlets that use alternating current and, as we covered above, the type of power outlet used, either 120V or 240V, depends on your electrical device’s power demand -- so let’s talk about a device’s power demand.

Lighter appliances or devices like refrigerators, toasters, TVs, radios, lamps are examples of devices that run on 120-volt circuits. On the other hand, your larger appliances with bigger, heavier power (wattage) demands like an electric dryer, water heater, or furnace. will require 240-volt electrical outlet. Also, nowadays homeowners may need to consider an electric vehicle charger in their home’s electrical plan. Therefore, here are three important facts about 240 voltage that may come into play:

  1. For recharging a 240-voltage circuit means a full recharge will happen more quickly.
  2. 240V means there would be less voltage drop or energy lost to overcoming resistance if you need a longer cable run to an electric vehicle charging port.
  3. And, again, with larger electric motors, 240V power circuits are preferred because fewer amps are required on start up.

US homes use AC 120V single-phase or 240V split-phase power.

While U.S. homes use AC current with 120V power -- they use two live wires not one as the term “single-phase” might infer. Remember, as we covered above,

in 1883 direct-current-advocate Edison patented a three-wire distribution system that used two 110V conductors with a neutral conductor to create a 220V direct current electricity system -- which the rival alternating-current-proponent, Nikola Tesla later adopted to provide 110-volt power to incandescent lighting as well as 220-volt power to major appliances. Then the 110/220 voltage became standardized as 120/240 voltage in 1967.

With this two-live-wire-and-one-neutral-wire configuration, normal appliances plugged into their 120V circuit receive their power from either one of these two live wires, whereas more power-hungry appliances (like electric clothes dryer, electric stove, electric water heater, etc.) receive their 240V power by utilizing both live wires. All electrical appliances and devices in your home operate off this single-phase power which powers both the 120V and 240V outlets.

Let’s take a closer look at your home’s single-phase or “split-phase” wiring.

A single-phase wire has three wires plus a ground wire within an insulated cover. One neutral wire (white) and two hot wires (red and black) provide power plus one grounding wire (green). Each hot wire conducts 120V of electricity. For the appliances like electric stoves, clothes dryers, and water heaters that require 240V to operate, those circuits are fed by both 120V hot wires. All the home’s other electrical appliances and devices which operate on 120V of electricity use only one hot wire and the neutral wire -- because of this configuration single-phase power is at times referred to as “split-phase” power.

Is 240V cheaper than 120V electricity?

Given that the 240V power divides single phase electricity into two separate 120V conductors that share a common neutral wire, here we should note that 240V gives a more efficient transfer of power. Remember Joule’s Law, “Power is equal to voltage times current” which means that twice the voltage will transfer twice the power.

This means if 240V wiring is used, then less current is required. That statement may momentarily lead you to think that it would be cheaper to use 240-volt power because it uses half the amps 120V uses.  As it turns out there’s not much cost difference between 240V and 120V usage because amps are not what electricity consumers pay for -- it is the wattage use that we pay for, and the wattage use is the same (for all practical purposes) whether you’re using a 120V or 240V circuit.

How to calculate load using Watts Law.

To calculate the electrical demand of an appliance we must consider the three main measurements of electricity volts, watts, and amps. Watts Law gives us a formula: amperage (A) x volts (V) = watts.

Review of relevant definitions

  • Amps is the unit of current flow.
  • Amperage is the strength of a current of electricity expressed in amperes.
  • A “volt” is a unit of electric potential.
  • Voltage (V) is the potential for energy to move (or flow).
  • A “watt” is the unit of measure for power. One watt (W) represents the rate at which work (say lighting a light bulb) is done when one amp (A) of current flows through an electrical potential difference of one volt(V).
  • Electrical potential difference (which can also be referred to as voltage, electric pressure, or electric tension) is the difference in electric potential between two points -- which is defined as the work needed per unit of charge to move a test charge between two points.

Using the amperage (A) x volts (V) = watts formula the available wattage of a given circuit can be calculated.  If you look at the list below you will note as the wattage demand on a circuit increases, you need to provide a circuit breaker with a higher amperage to protect that circuit.

So, let’s look at this list below and maybe start with an example of an electronic device that draws 3 amps at 120 volts which would be rated 360 watts. So, this 3-amp 360-watt electronic device can lead our list as an example. It would be powered by a 15-amp 120-volt circuit. Its 3 amps of required current flow multiplied by 120 volts would equal 360-watts using the Watts Law formula (the formula’s reordering variations are shown just below the following list.)  

  • 3-amp 120-volt circuit:   3 amps x 120 volts =  360 watts
  • 15-amp 120-volt circuit:15 amps x 120 volts = 1,800 watts
  • 20-amp 120-volt circuit: 20 amps x 120-volts = 2,400 watts
  • 25-amp 120-volt circuit: 25 amps x 120 volts = 3,000 watts
  • 20-amp 240-volt circuit: 20 amps x 240 volts = 4,800 watts
  • 25-amp 240-volt circuit: 25 amps x 240 volts = 6,000 watts
  • 30-amp 240-volt circuit: 30 amps x 240 volts = 7,200 watts
  • 40-amp 240-volt circuit: 40 amps x 240 volts = 9,600 watts
  • 50-amp 240-volt circuit: 50 amps x 240 volts = 12,000 watts
  • 60-amp 240-volt circuit: 60 amps x 240 volts = 14,400 watts

So, if amps (A) multiplied by volts (V) equals watts (W)

or A x V = W

We can reorder the formula as:

Watts = Amps x Volts or

Volts = Watts / Amps or

Amps = Watts / Volts

This blog’s information may be important to you if you are considering calculating the amount of solar power generation capacity you would need to correctly size a solar powered generator system that would meet your household power needs.

Let’s look at another example. We’ll say the rating on the manufacturer’s face plate is 8.3 amps. So, using the formula (A x V = W) we multiply 8.3 amps by the home’s circuit voltage of 120 volts and we arrive at 996 watts. However, you might only use that appliance (let’s say it’s a microwave) for only 2 hours a day so then you would multiply 996 watts the 2 hours of use per day to arrive at 1992-watt hours (Wh) per day for that microwave appliance.

 Let’s look at how to calculate a circuit load.

For any given household branch circuit, you can identify the appliances and lights and other devices that will be used by that circuit.  Then you want to calculate whether some of these devices will be running at the same time.

For example, let’s look at a hypothetical 120V bathroom circuit. It would not be unusual to have the bathroom fan vent (120-watts), a three-light over-the-sink light fixture (three 60-watt bulbs = 180-watts), and maybe even a 1500-watt hairdryer (using the variation of Watts Law: watts divided by volts equals amps would be 1500W divided by 120V equals 12.5 amps). 

Could electronic devices on the circuit be drawing power at the same time?

Because in our hypothetical bathroom all these fixtures and devices could be turned on and drawing power at the same time it means the 120-volt 15-amp bathroom circuit with a total capacity of 1800-watts would be maxed out. Therefore, an electrician would add a 20 percent safety margin to ensure that the maximum load is no more than 80 percent of the circuit’s available amperage and wattage.

So, in our example a 20-amp 120V circuit which would provide 2400-watts of available power would be used instead of a 15-amp 120V circuit with only 1800 watts of available power. With this upgrade, the 1800-watt load could be easily accommodated with a 25 percent safety margin remaining, and you would not have to worry about inconveniently tripped breakers.

The lesson we can take from this last example is the importance of slightly oversizing your electrical systems to give a safety margin. This safety margin also ensures that if the next appliance or device you buy is slightly larger or more powerful than your current one, your electrical system can handle it.

Let’s look at an example of a dedicated 240V appliance circuit.

If we have a 240V electric water heater rated for 5,500-watts we can calculate the requirements this dedicated appliance circuit will need using the above Watts Law formula A=W / V.

22.9 amps = 5500 watts divided by 240 volts

So, because this dedicated appliance circuit needs a 20 percent safety margin the circuit would need to provide 27.48 amps (that is 120 percent of 22.9 = 27.48 amps). This means a 30-amp 240-volt circuit would be needed to serve this 5500-watt water heater on this dedicated appliance circuit.

Appliances with motors can draw extra power on start up.

When we think of our home’s different electrical appliances, several will have a motor, like refrigerators, air conditioners, washers, dryers, dishwashers, disposals, etc. Most of these motorized appliances, according to the National Electrical Code, need a dedicated circuit (either a separate 120V circuit or for heavier electrical load appliances 240 V).

To determine the correct specifications for a dedicated appliance circuit, review the appliance’s power demand and ensure that demand can be accommodated within the circuit’s capacity. Also, you will want to add the 20 percent margin as a safety buffer to ensure the appliance’s demand is within the circuit’s capacity even when it is pulling more power in its startup phase.

Appliances’ critical data can be found on their face plate.

To find an appliance’s wattage requirement ratings locate its face plate. (Ironically these face plates are often located on the back of the appliance.) The face plate should have the appliance’s critical data. If you know the appliance’s amperage rating and you know the voltage of your household circuit, then you can figure the wattage capacity required for the safe operation of the appliance.

Information needed to correctly size a solar powered generator system.

All the information we have discussed in this blog may be important to you if you are considering calculating the amount of solar power generation capacity you would need to correctly size a solar powered generator system that would meet your household power needs. The quickest method if you’re looking at a whole home solar system is to look at your current electric bills and see how many kilowatt-hours (kWh) of electricity you use. (If you do not keep your electric bills, you can probably access your account online to retrieve this information.)

Annual kWh usage easiest way to right-size whole-home solar generator.

To give you an idea of the average annual kWh usage, according to the U.S. Energy Information Administration in 2020 the average was 893 kilowatt-hours per month, or about 30 kilowatt-hours per day, which is about 10,680 kWh per year.  So, you can check your own electric bill information to find your household’s exact usage and with that information you can calculate what your power requirements would be for a whole-home solar powered generator system.

Powering essential appliances and devices with solar powered generator.

If you are not interested in a whole home solar system, but just want to power certain important appliances and devices during an emergency power outage or if you want to take certain appliances offline and run them on solar power during peak use times, then you can use the above information to calculate the wattage the different branch circuits in your home’s electric panel draw and make sure you correctly size your backup solar generator system.

Because Nature’s Generators are powered by clean renewable solar powered energy, they emit no toxic fumes and they are quiet when they operate, you can roll the portable Nature’s Generator into your home and simply plug in which ever devices and appliances you select without having to pay for any installation. Our systems were designed for this -- easy-peasy.

(IMPORTANT SAFETY WARNING: While you can safely bring a solar-powered generator into your home, we want to be clear that to keep your family safe you can never bring a fossil fuel (gas, diesel, propane) powered generator into your home or even locate it outside your home within 20 feet of a door or window. There have been far too many tragic stories about families being killed by the carbon monoxide emitted by fossil fuel powered generators.)

With the information provided in this blog you can make sure you size your generator so that it can handle the electrical load of the devices you will want to plug in and power every day or during an emergency blackout.

A second way to use our Nature’s Generator solar powered systems is to purchase a power transfer switch kit. (We do recommend using a licensed electrician for this installation because our Power Transfer Kit will tie directly into your home’s main electrical panel,) With a Power Transfer Kit you can select which of your home’s branch circuits that you want to power.

Solar powered generators and power transfer kits.

Nature’s Generator’s Power Transfer Kits are extremely affordable. There are several different sizes depending on the Nature’s Generator you select.  A 4-breaker Power Transfer Kit for our starting Gold solar powered generator system is only $239.99.

What a Power Transfer Switch does is make it easy for the homeowner to prioritize their home’s most important household circuits to be able to transfer power from the failed utility grid in a blackout to be able to power a home’s most essential devices and appliances by only flipping a switch – it truly makes transferring the power from the grid to your solar-powered system as simple as turning on a light.

The other thing Nature’s Generator’s Power Transfer Kits can facilitate is the ability to take these selected important circuits offline during higher utility-rate times during the peak-use periods (usually between 4 and 9 PM) to keep the homeowner from having to pay these higher Time of Use rates.  Again, switching from utility grid power to your own solar-powered generator system can be done by only flipping a switch.  With our extremely affordable Power Transfer Kit you will substantially lower your electric bills even if you don’t opt for a whole-home solar powered generator system.

How to use the above information to right-size a generator system.

We can take some of the lessons we’ve learned above and apply them to calculating the right-sized solar powered generator system either as a partial backup system to keep some of your important devices running during a blackout and to take devices offline in peak-use times to avoid higher-rates, or to create a whole-home solar system that could be capable of running your entire household -- offline if necessary.

The information in this blog can help you correctly size a solar powered generator system to harness the free energy of the sun to help power your household. Millions of people around the world are transitioning their homes to cleaner, greener, renewable energy to power their homes and keep their families safe during power outages and to help combat the climate crisis we currently face.

Nature’s Generator solar powered generators are affordable.

We want you to be aware that Nature’s Generator has a complete line of different size solar-powered generators that can be scaled to meet your household’s power needs. Each of our generators are stackable and can be run in a parallel operation meaning that you can daisy chain two or more of the same model generators to get the power that you need.

Our gold system which includes the 1800-watt portable generator and a portable solar panel and the connecting cables, starts at only $999.99. All Nature’s generator systems are scalable and can be infinitely expanded -- even our newest Powerhouse ($2999.99) which was designed (as the name suggests) to power a house can be daisy-chained to expand its capacity.

Combat climate change --- transition to renewable solar powered energy.

Why it is so important for all of us to do our part and transition to clean, green, renewable energy is our world is facing a global climate change crisis that our relentless burning of fossil fuels for power and transportation has been exasperated by our continually releasing tons of greenhouse gases into our atmosphere. Scientists have told us we have less than a decade to try to correct this problem and stop adding to the accumulated greenhouse gases in our atmosphere -- or we will reach a tipping point where things will get exponentially worse.

Even now climate change is dramatically changing our “normal” weather patterns and replacing them with more extreme weather patterns – longer drought periods, increased intense rainfall causing flooding, more extreme hurricane systems, etc. Because we have a short time to correct the climate change crisis, we must transition to clean renewable energy to power our lives so we can help clean up this environmental mess ASAP.

Affordable solar power to the people will help combat climate change.

Nature’s Generator wants to be part of the solution. Nature’s Generator has a complete line of different sized solar powered generators that can be scaled to meet your household’s power needs from our Standard Gold system to our whole-home Powerhouse designed to power a house. Each of our generators are stackable and can be run in a parallel operation meaning that you can daisy chain two or more of the same generators to get the power that you need. Most importantly, our products are affordable to the average family.

We understand that we can have the greatest product in the world, but if it is not affordable for the average family -- then it will not be used. We want our solar powered generators to be affordable so that everyone can afford to help combat climate change. 

Nature’s Generators are affordable ecofriendly wunderkinds.

Each Nature’s Generator is a clean, environmentally friendly, solar powered wunderkind of a generator that does not require professional installation which will also save you money.

If you remember only one thing about our Nature’s Generator company, please remember this – our goal is to give everyone access to reliable electricity by harnessing the free power of the sun to provide their family with affordable reliable power for everyday life and for safety in the event of a blackout emergency. To this end our company’s founders have not increased the price of the Standard Gold system for over seven years! So, with our products think: “Affordable”.

If you want that idea in the form of a slogan, think:                                                      

“Nature’s Generator, the most power for your dollar.”


We started this blog to examine 120V vs 240V power differences and to touch on several things people should know about their home’s electrical power systems. We segued into how to right-size your solar powered generator systems and how the renewable-energy solar-powered Nature’s Generator systems can help combat climate change.

To wrap up, one last planet-saving product plug.

At Nature’s Generator we fight to keep our prices low and affordable to give everyone the ability to harness the free solar power from the sun. We understand that if everyone can afford to transition to a solar powered generator system, then collectively we can make a faster transition to clean renewable power so we can help reduce greenhouse gases and help fight climate change. So, if you want to remember our prime motive in the form of a catchphrase from a bygone era it would be:

 “Solar power to the people!”

Please check out our affordable products at