FAQs on Efficiency or energy savings of 240 Volt vs 120 Volt appliances & devices:

This article weries describes the difference between wiring an electrical motor, such as a well pump, to operate at 120 volts compared with 240 Volts and answers the common question of whether or not wiring an electrical device to operate at higher 240 Voltage level will save on the electrical bill by using less energy.

The short answer is no, and details are provided below. Sketch courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

FAQs: Does 240V Save Electricity over Wiring at 120V?

These questions and answers about electrical efficiency vs. voltage wiring and other differences between 240V and 120V wiring were posted originally

at EFFICIENCY of 120V vs 240V EQUIPMENT - you will want to review that information.

On 2018-07-09 by Chris - buy a motor rated to be converted between 120 & 240VAC

In the example of the 120/240 volt ac motor, yes you would have twice the voltage and twice the amperage if the motor was rated for 120 vac only.

A dual voltage motor will have another set of taps to convert it to 240 vac so the current will be halved and the motor will operate normally. Purchase motors with dual voltage if you want more options.

If you double the voltage and the resistance stays the same the current will follow the voltage and double also.

Watch out: So for example a space heater with only a 120 volt rating that is connected to 240 volts ac will overload and fail caused by overheating and possible fire hazard.

On 2018-07-03 by (mod) - can I plub my 230V baseboard heater into 120V circuit?

No, Laurent.

Watch out: More likely you'll blow a fuse, trip a breaker, or at worst, set the building on fire. Don't do it.

On 2018-07-02 by laurent

if I have a 230v 1000w baseboard will it give out 500w if I plug it on 120v

On 2018-02-28 1 by lorne kuntz

Mod: so i have very little knowledge of elec but i was told that a meter only reads one side of panel , then doubles for a total usage , or something like that ..

so if not balanced whitch is hard to due with a 110 pump on one side ,with a heavy draw at start up .. and probaly starts more than one may think ,

also does not have its own breaker so i need to run its own circuit anyway ,my only real cost is a 220 breaker as i have wire and a 110 breaker and wire for 220 install but the double breaker may be as high as 80.00 ..not sure about that .

And a plug or disconnect,, if i am away i always unplug pump ,, any comments apreciate your input ,,thanks

On 2018-02-27 by (mod) - 110 vs 220 running for 1 hour equals same cost

Lorne

Perfectly fair and interesting question. I'm doubtful, though, that the voltage difference during motor startup will make a measurable difference in one's residential electric bill. There are better energy-savings targets of opportunity like finding and fixing drafts.

On 2018-02-27 by lorne kuntz

Read your articale but ,, 110 vs 220 running for 1 hour equals same cost .. understood .

but a 110 at strart up draws higher amps for a short pieriod .. does this translate into more watts used ,due to pressure system constantly start and stop , and in this case would a 220 make a difference or not realy ...

On 2017-11-25 by (mod) - 220VAC motor will not work properly nor safely if wired to 120V

Al,

No.

If the fan motor is designed to run only on 230 volts it's not going to work properly in or safely at half that voltage. Some Motors are wired such that you can actually switch between the voltages. Check the wiring diagram and installation instructions for your fan.

An exception is that some motors have tappings that permit changing the motor wiring to run on either 120VAC or 240 VAC but they will be different wire connections.

On 2017-11-24 by Al - can I run my 230V van on 120V?

I have a fan that is marked 230 volts .is it ok to use vers having to by on the to run on 120 volts

On 2017-06-06 by (mod) - If the appliance is designed to run on just 120VAC and you connect it to 240VAC

If the appliance is designed to run on just 120VAC and you connect it to 240VAC (which should be impossible unless you cut off or change the appliance line cord or wall plug) there is a good chance you will burn up the appliance and risk a fire or shock.

If you're lucky a fuse will blow or a breaker trips before the appliance catches on fire.

That's because you are in essence more than doubling the watts delivered to the 120V appliance on the 220V circuit.

That means that an appliance with an electric motor will probably burn up the motor in short order, or an appliance with a heating element like a toaster will burn up quickly.

You can, however, buy a step down transformer that connects to the 240V supply to step down the 240V to 120V and then safely use your appliance. This problem comes up when people take a U.S. or Canadian appliance like a toaster or hair dryer over to the U.K and then try to force-plug it into a UK circuit. Don't do that.

On 2017-06-06 by Anonymous

What happens if I use an appliance with 120 volts in 240v supply

On 2017-05-08 0 by (mod) - why industry uses 220V instead of 120V,

Thanks Angelo, that's a point worth mentioning.

On 2017-05-07 by Angelo

Simple answer why industry uses 220V instead of 120V, it's because you can use smaller wire on a 220 circuit of equivalent power.

Copper wire is not cheap. Industrial equipment typically has larger power loads, they need to minimize installation costs by running the highest voltage requiring the smallest wire. Same reason overhead power lines are at higher voltages.

If you run your pump at 120V you may need 12 gauge wire, but at 220V you would get away with 14 gauge. Much cheaper.

On 2016-12-22 by (mod) -

Hi Nigel.

The wiring should be fine for a 240v bulb, as the current will be about halved, but you may need to change the bulb socket,

I would also check any other controls or switches to be sure that they are rated to handle 240v

On 2016-12-21 by Nigel

Hello. I live in UK. A friend bought an artist episcope with a 250 watt bulb.

He was running it on a step down transformer here in UK. The bulb was 120 volt. If I put a Uk plug top on the USA wiring and get 240 volt bulbs,(still 250 watt), will this work? There is an on/off switch in this circuit. I was thinking that the wiring would usually be carrying higher current. Thanks

On 2016-12-15 by (mod) -

Tom, quoting the article above

The watts consumed (and therefore the size of your electric bill) for running a water pump or other electric motors will be almost exactly the same regardless of whether you are running the pump wired at 120 Volts or 240Volts.

On 2016-12-15 by TomP

I am looking at purchasing a wall mount convection heater, and can get either a 120 volt unit or a 240 volt unit. I have
heard from people that know electricity better than I that it's cheaper to run say a heater as this one on 240 volt.
Can you tell me if this is true or should I stay with the 120 volt usage items.

I personally know very little about electricity other than flipping a switch. Was bitten by a 120 volt wall socket via a fork when I was two and haven't experimented any further with it since.
Thanks much.

On 2016-12-09 by (mod) - Using a U.S. appliance (120VAC) in the UK (240VAC) using voltage converters

Michael

We can't give a number because you don't give the amperage draw of the motor. There are several good voltage-to-watts calculators online but you'll need a bit more data.

On 2016-12-06 by Michael Hadad

Here's my question to which I have not yet been able to find an answer:

I moved from the UK where as most of you will know, the Voltage is supplied at 240. Now I have brought with me most of my household appliances, and one of the, a mixer, has had its motor burnt due to our fault and not due to an improper connection etc. Obviously I am using a very capable step-down transformer.

Now that I am looking to replace the motor on said mixer, rated at 800W running on 240V, what would the aquivalent power be in 110/120 to enjoy the same mixing power from the machine?

I assumed that I needed a 1600w motor, but nowhere you will find home appliances with such high powered motors here in the USA.

Actually i found the opposite to be true, that most appliances are rated in wattage much lower than a similar appliance in the UK.

I would greatly appreciate a clarification. Thank you

On 2016-09-12 by Aaron Sprague

Another benefit of running 240v vs 120v is you can run twice the wattage through your main panel i.e. your service entrance wire using 240v.

For ex. If your panel is rated for 150 amps @ 120v you can use 18,000 watts at maximum amperage (however, using 80% or less amperage than a circuit's ampacity is a safe recommendation). On the other hand, 150 amps @ 240v will allow 36,000 watts @ maximum ampacity. To do this however you will need twice the number of slots on the main panel.

On 2016-08-27 by (mod) - voltage supplied to a building doesn't determine how much electricity is being actually used;

Bobbie, The voltage supplied to a building doesn't determine how much electricity is being actually used; rather it's the amount of "stuff" that's plugged in and running that uses electricity.

You might take a look at electric meter readings.

On 2016-08-26 by Bobbie Burrell

I have a my house friends on 110 and I have an RV in my on my property and it's running on a 240 is the RV on the 240 using more electricity than me on the 110

On 2016-07-15 by (mod) -

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies,

Question: Can I change a motor from 120V to 240V

(Apr 16, 2014) Paul L said:

If a motor has been running on 120 volt is it ok to change the voltage to 230 volt it is a dual voltage motor.

Reply: maybe

Paul

Maybe. Check the data tags.

Some motors can be re-wired to switch to 230V operation from 120V but DO NOT just change the wires at the same terminals. You may burn the thing up. Check the motor data tag for what it is capable of handling and check the installation or wiring guide for what jumpers to move or wire connections to make.

Question: wire for 240V when installing new equipment

(May 3, 2016) Cookie said:
Good article, and I agree with your assessment.

However I would take issue with your statement that rewiring would likely require upgrading wires and components.

My understanding would be that increasing voltage would decrease the required wire size, which in my opinion would be the best reason to use 240. So it may not make sense to rewire for 240, it if you are installing new equipment, 240 does make sense.

Reply:

Well put. A concern is that we don't and can't obtain 240V on a conventional 120V three wire circuit - that circuit breaker occupies just one 120V position in the electrical panel;

you'd need to occupy two positions in the panel and switch to a 240V double pole breaker, converting the circuit and marking wires accordingly.

Question: will a 240V motor run when connected to a 120V breaker?

(June 16, 2016) Easy said:

What if a pool pump is set up already for 230 volts and gets connected to a breaker for 120 volts , will the pool pump turn on ?

Reply: no

Easy

SOME 230V motors might run weakly when only half-voltage is supplied; more likely the motor hums, doesn't run, and might be damaged.

Question: Should I replace my 230v pump with a 120v pump?

2016/07/12 donny47% said:
230v spa pump vs. 120v. Should I replace my 230v pump with a 120v pump?

Reply:

Donny,

In the EFFICIENCY of 120V vs 240V EQUIPMENT article above be sure to read the section

"So what advantages do we get from running an electric motor at 240V rather than 120V?"

...

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