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Electric Power & Utilities/240V VS 120V Power Consupmtion


Hello Bob, I was told that cost wise a 500W at 240v appliance will cost same as 1000w 120v on my electricity bill and I not certain about it...

Can you please clarify: If I run 2 appliances for One Hour. One is rated 500W at 120v and the other 500W at 240V  - What will be the cost on my electricity bill? Is the first (120v) going to cost me half than the other (240v) or same?

Thank you,


Wattage consumption is the bottom line and your "appliance" scenario  illustrates that fact perfectly. When you run the numbers through the formula's below the voltage and the amperage numbers can be different but the wattage still comes out the same. In other words voltage has a direct effect on any given appliance's amp draw but the wattage always stays the same. Lets say your appliance example is a waffle iron and you have the option of hooking it up for 120 or 240 volts. The iron will always consume 500 watts wether its hooked up for 120 or 240. The difference is the amp draw. Notice higher voltage less amps. Lower voltage more amps. But the bottom line remains the same.

It is a common misconception among lay people that an appliance will consume less power hooked up to the higher voltage which simply isn't true and the numbers below bear that out.

500W/240= 2.08 amps  ,  500W/120= 4.166 amps


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PV Electric Bob Mossman


Master Electrician licensed (29 years) 6165B Contractor in Closter New Jersey with 38 years total experience in Residential - Commercial - Industrial work. Emergency Service - General trouble shooting and repair work - Paddle fans - Kitchen & Bath exhaust fans - AC lines - Smoke detectors - Telephone lines - Cable TV lines - Computer network cabling - Exterior lighting - Recessed lighting - Security lighting - (200 - 150 - 100 amp service up grades) - Electric Heat - New circuits - New appliance hook ups - Back up generators - and more ! FREE ESTIMATES Fully insured 201-358-1552


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