So you are wanting to convert volts, amps, and watts. This is a rather simple conversion you can do with a calculator, you don’t need any special devices, but there are some devices out there that will convert volts, amps, and watts for you. Every electrical device in your home should have it’s voltage and amperage or voltage and watts printed on it. If not you will need to use a multimeter to find the voltage and amperage or voltage and watts.

But for those electrical devices in your home that have volts and amps or volts and watts printed you can convert amps to watts or convert watts to amps depending on what measurement you want.

If your electrical device in your home has the voltage and amperage printed on it you can convert this to watts by multiplying the voltage and amperage.

Voltage * Amperage = Wattage

So if you have a laptop that has 20 volt 4.5 amp printed on the power supply then that power supply is capable of using 90 watts.

20 volts * 4.5 amps = 90 watts

Pretty simple to convert volts and amps to watts. For those of your electrical devices that have voltage and wattage printed on the power supply, you can convert volts and watts to amps simply by dividing the wattage by the voltage.

Wattage / Voltage = Amperage

Now if your laptop’s power supply has 20 volt 90 watts printed on it, then you can take the watts and divide them by the voltage to get the amperage.

90 watts / 20 volts = 4.5 amps

Now if your electrical device does not show the voltage, amperage, or wattage you can use a multimeter to measure the voltage and amperage, then convert this to wattage.

Thank you for reading this tutorial on how to convert amps, volts, and watts. If you have any questions please leave a comment on this conversion formula and Go Green in Your Home will try to respond back as soon as possible. For more tips on saving electricity or ways to go green continue reading through Go Green in Your Home! Have a great day!

January 3rd, 2017 at 6:19 PM

Garry,

watts is the same whether it’s 110VAC or 12VDC, but your 27watt light is probably pulling 27watts, but to make that 12VDC from 120VAC is using power as well. You have a power inverter installed that is taking the 120VAC and converting it to 12VDC, the efficiency of this power inverter will not be 100% efficient. So you are using electric just to convert from 120VAC to 12VDC. The best I’ve seen is 95% efficient. So you’re using 5% more electric just to convert. So your 27 watt light bulb is using 27 watts itself and another 1.35 watts to convert the power totaling 28.35 watts. That’s if your power inverter is 95% efficient. I’m sure you can look up the make/model of yours and see what it’s efficiency is.

To answer your question about leaving a 27 watt bulb (using 12VDC) and a 100 watt light (using 120VAC) the voltage doesn’t matter, 100 watt is more than 27 watts. Hope this helps. Thanks for visiting!

November 17th, 2016 at 1:52 AM

Im pulling my hair out trying to figure out why my RV is so expensive to run off of 120 (AC) volt…it has a converter that flips the 120AC to 12 volt DC…..if a 1156 bulb that pulls 27 watts on 12 volts (DC) is on….what is it the same as in 120 volt AC….like if you leave a 100 watt light bulb on is leaving a 1156 (27 watt 12 volt) bulb more or less power? is this confusing or did I say it all right? lol

September 5th, 2016 at 12:37 AM

Dewald,

You’ll need a transformer and a disconnect breaker. I don’t know how many amp service you are wanting, but you’ll need to know this to size your wire, transformer, and breaker. I’d recommend breakers on the primary and secondary of the transformer.

August 7th, 2016 at 9:03 AM

I need to covert incoming 150kw to usable 240 volt. How do you do that? What equipment is needed if the 150kw is fed from a sub-station? Please help.

July 12th, 2016 at 5:40 PM

Smith,

I’m going to guess that you are wanting to know the difference between plugged into socket or plugged into grid? You don’t plug into a socket. You can either be off-grid, or on-grid. Off grid is you do not have anything from electric provider, just your power you generate and store in batteries. On grid is where any excess you generate goes back to electric company and you get paid for it. If you don’t generate enough you pull from the electric provider like you normally would.

July 12th, 2016 at 5:37 PM

Stephen,

There is a kwh calculator on my website here that you can plug your numbers into and it will calculate it for you. For me to calculate this for you I’d need to know the voltage. 50amps * voltage = watts, which you can find that formula on my site as well.

July 12th, 2016 at 5:31 PM

Chinna,

100kwh = how many of what units? I don’t know what unit of measurement you are wanting to convert to.

July 12th, 2016 at 5:11 AM

deference between solar plugged into socket or to be plugged into grid to run the house

July 7th, 2016 at 6:45 PM

If I use 50 amp constantly for one hour how many kw have I used

June 29th, 2016 at 3:29 AM

100kwh=how many units

May 14th, 2016 at 11:08 PM

Vikrant,

You can use a MPPT charge controller that will allow you to charge 12 volt battery bank with 24 volt solar panels.

March 14th, 2016 at 3:46 PM

Hi,

I have 5 pannels of 300w 24 volt my problem is how to charge my battery bank which is at 12v if i make my battery bank of 24 volt then i wont be abel to run my fan as it oprates at 12volt

Secondly distance of farthest fan from battery bank is around 100mtr is it ok to connect dc fan with battery at this distance….pls help a diagram will be great help

March 12th, 2016 at 10:01 AM

Kris,

I’m not sure what you mean by 91,000 watts? Is that 91,000 watt hours? 91kWh? Yes, people can use alternators to generate power, you still need a method of turning the alternator. If you put fan blades on it, you’ve basically made a wind generator.

As far as the fan being around 100 meters away, that should be fine as long as you have adequate gauge of wire to carry the required amperage. I would also be sure to have a fuse or circuit breaker at the beginning of the circuit closest to the battery in case that long wire gets a ground or a short it will pop the fuse or breaker so you don’t damage your equipment or get hurt.

March 12th, 2016 at 9:57 AM

Vikrant,

First we need to calculate how much power you’ll be using.

There will be 104.16 amps being drawn constantly, so make sure your wiring is sufficient, fuses, etc.

25watt x 10 hours = 250 Wh / 1000 = .25kWh each fan

.25 kWh x 50 fans = 12.5kWh each day

Your 12v 150Ah battery holds 12volt x 150 A = 1800 Wh / 1000 = 1.8kWh

You need 12.5kWh each day and each battery is 1.8kWh. So you’d need 12.5 kWh / 1.8 kWh = 6.94 batteries.. So 7 batteries.

This is perfect charge, discharge, no surge, efficiency of charger, temperature of batteries, etc. All if those things will effect tgevamount if power you truly get from your batteries.

Now you have 7 batteries required to be charged. Which will most likely be 8 or 10 batteries after you factor in all those other factors I mentioned. You can either put 2 batteries in series to make 24volt which will leave you with 4 or 5 of those sets to wire in parallel. You could also take 4 or 5 batteries, wire them in parallel which now gives you 2 sets to wire in series. Now use your 24 volt panel to charge.

You will also need to know your 300 watt solar panel will not keep up with this load. You will need around 1283 watts if you are generating 100% from the panel 6 hours a day. Not sure if your area and sunlight you get, as that will effect this number as well.

March 10th, 2016 at 5:18 PM

I’m trying to figure out what kind of power supply I need to run my house. I use 91000 watts every 30 days. I’ve seen people use high out put alternators from a vehicle to charge car batteries for the house then they put in a power converter.

March 9th, 2016 at 2:46 PM

Hi,

I want to run 50 DC Fan (12 Volts 25 watt)

I have 12 volt 150 Ah battery.

I need to Know…?

1) How many batteries do i require to all the fans for

Ten Hours every day.

2) How can i charge these batteries using solar panel

I have 300 watt 24 Volt solar panel.

12 Volt panel is not available in my area :(

February 4th, 2016 at 10:58 PM

Gail,

38 amps * 243 volts = 9234 watts

9234 watts / 1000 = 9.234 kWh

9.234 kWh * $0.11 = $1.01574 per hour

You can use the kWh calculator on my site to do this calculation for you. It will tell you cost per month and year.

I hope this helps you. How many miles do you get from 1 hour charge? You can then use that to calculate how much it costs per mile to drive this car.

January 28th, 2016 at 8:59 PM

I want to know how much it costs to charge my car per hour. It charges at 38 amps, 243 volts. and I pay about .11 kWh I multiplied 38*243=9196 * 60(minutes) * 60 (seconds)/.0000036 (1mega Joule) to get 11.92 kWh. Do you think this is correct?

November 18th, 2015 at 7:11 AM

Speedy,

They both would he the same. 100 watt draws 100 watt regardless of the voltage.

October 28th, 2015 at 7:12 PM

so I have a question regarding 110vac vr’s 12vdc? if Jack was to run a 110ac 100 watt bulb and Jan was to run a 12vdc 100 watt bulb would it cost the same per hour?

September 16th, 2015 at 10:38 PM

Micah,

Hi, thanks for visiting my green site! First, I’m going to assume that in your “in an emergency” scenario, you’re wanting to have enough electricity stored in batteries to power what you need for 3 days without getting a charge from solar panels. So first we need to figure out how much power you’ll use in 3 days.

The refrigerator is 1,725 watts? Seems kind of high. That may be the max surge or maybe what it will use in 1 day? I’ll use this spec as you have it, but I think something is wrong with it. Your refrigerator alone at 1,725 watts running for 3 days will consume 124.2kWh. 8-10 LED lights being turned on and off is hard to give an exact number, but we’ll use 1.5kWh in 3 days for LED lights, 450 watt heater for 5 hours each day, will consume 6.75kWh, a 450 watts blender for 30 minutes a day will consume 0.675kWh, and finally an 80 watt crockpot used 3 hours a day, will consume 0.72kWh.

So we now have a total of 133.845kWh used in 3 days. You’ll need to be able to store this amount. Also being that your battery bank will be DC voltage, you will need an power inverter which will give you AC voltage. These are not 100% efficient, so you will loose a little bit of your power. If need roughly 135kWh you may need to store 150kWh to be able to supply 135kWh due to the efficiency of the power inverter. I think some of them may be up to 95% efficient. So you’ll need to factor that in.

So if you need 133.845kWh, with an inverter at 95% efficient, using 12VDC batteries, you will need 3 95AH 12VDC batteries wired in parallel to last you 3 days. If my calculations are correct! I’m not too great with batteries yet. They have their own efficiency and can only be discharged to different percentages (you don’t want to drain them completely). Hope this helps you out! Please come back and visit.

You can use my Electric Formulas and Calculators to do most of what I’ve done here for you. Except the actual battery bank part, sorry, I’ll try to work on making a calculator for this right on my site to make it easier for visitors to get this information.

September 12th, 2015 at 6:03 PM

Hey. I found this page online after searching for a way to figure out what voltage/how many batteries I need for storage on a solar power system. I’m looking at a system with 12 310 watt panels, to get 400 kWh monthly. We get between 4.2-5 hours of sunlight average. I’d like to have enough stored in the batteries to last three days in an emergency, but all of the other sites I’ve found to calculate battery amounts seem weird in their results.

A little more information:

All that will be running off of solar is a fridge (115 Volts, 15 amps – 1725 watts), 8-10 LED lightbulbs which will only be on intermittently, an electric heater during the cooler months (and only when necessary, as I’m hoping to take care of most of this with passive solar), which operates at 450 watts, and occasionally a blender (450 watts) and crockpot (80 watts). I also want a solar water heater, but haven’t figured out where to even start with that yet. Cooking will be propane, so the range doesn’t factor into this.

I also want the option to tie into the grid at RV parks and the like, but want to be entirely capable of generating full capacity with solar. I just can’t figure out the batteries for the life of me.

July 17th, 2015 at 7:32 PM

Revathi,

Usually amps or watts are printed on a tag, if not you could look up the year, make, and model of the refrigerator and see if you can find any specifications for power consumption. You could also measure using an ammeter or even something like the kill-a-watt, but I’m not sure what voltages the kill-a-watt is made for.

July 15th, 2015 at 7:36 AM

Hi

I have a small fridge which consumes 250 volts. How do I know how many amps required as the wattage is not printed anywhere?

Basically, my query is how do i know for a fan or a light, it need to be connected to 5 amp.. or 7 amp.. so i would like to calculate it

June 24th, 2015 at 12:32 AM

pls i want to build a device that can convert current to voltage and the amount of current use.

July 24th, 2014 at 11:53 AM

Afnan,

If you your pumping station consumes 150kw for 8 hours/day, 365.25 days a year and your cost is $0.45/kWh your kWh for a year would be 438300 kWh and would cost $16,436.25/yr. You can use the kWh calculator on this site using this link http://gogreeninyourhome.com/electricity-conversions/calculator-to-calculate-kwh/ you just enter your data and it will calculate this for you!

July 18th, 2014 at 9:19 AM

Hi, My pumping station consumes 150KW. It runs 8hr/day,30days/month & 365 days/year. The cost is .45 So what will be my KWH and per/year cost.

May 27th, 2014 at 4:57 PM

Nice job!

January 22nd, 2013 at 9:41 PM

Kris

This depends on what size batteries you have and how many. It also depends on how much you’re using on average.

December 25th, 2012 at 8:47 PM

Hello, We live off the grid and have a 48v solar system with back up batteries. In the evening when the sun has set and we look at our inverters it says the batteries are at 50 volts (which is fully charged). My question is how can I translate that into available watt hours? Meaning how much electricity can I use before I run out of electricity? Our system will stop running, to protect the batteries, when the volts drop down to 45.

Thank you, Kris

October 15th, 2012 at 8:25 AM

Is power factor make any effect on utility bill for residence.

September 27th, 2012 at 7:10 AM

I am an ancient wireless fitter, so do not comprehend the modern 200va . I wish to build a power supply capable of supplying 28 volts at a maximum of 25 amps.Can you please tell me what transformer would I need.

June 16th, 2012 at 10:53 AM

Garth Blain,

Converting watts to amps or amps to watts is the same for AC power and DC power.

May 29th, 2012 at 5:44 AM

Thank you for a comprehensive coverage of the subject. I still have a question though. Dividing watts by volts to calculate current drawn (in amps) is fine for DC but in the back of my mind there is a question about an adjustment needed in the case of AC. What would the current draw be for a device of 3000 watts at 220v AC?

I would be so glad to have your response.

Garth Blain.

May 21st, 2012 at 10:47 AM

Hi, thanks for replying

Sorry yes I’ve got a 500w inverter I’ll be using. the thing is thier main lights in a shop an also I’ll be having more solar panels to my 30a charge controller an adding more battery’s, so I can run a small LCD screen (for CCTV ) an a freezer, aswell as lights , I’m starting with 6 lights, how long would they last for? I’m wanting to run 6 11w 220v for 9hours on a 110ah battery is that possible ? Cheers

May 20th, 2012 at 10:20 PM

Rich,

The lights would not operate properly if you connected them to a 12VDC battery. You would need to use an inverter to step up the voltage and to create AC power. A 12V battery is DC, where the lights are 230V AC. You can buy an inverter to go from 12VDC to 230VAC and then be able to run the lights. But buying an inverter just to run some lights I think is silly. I would recommend buying 12VDC lights to connect to the battery. You could find many different lights to run on 12VDC. Even car headlights are 12VDC. Depending on what kind of lighting you need. You can search on amazon.com and find all kinds of 12VDC lights.

May 19th, 2012 at 1:52 PM

Need help I’ve got 6 – 11watts lights 230volts. that I want to run off a 12volt battery 110ah how long will it last for ??

May 10th, 2012 at 8:00 PM

Brian V,

If you dropped 5amp off of each phase that’s

480volt x 5amp = 2,400watts saved

2,400watts x 12 hrs x 365.25days / 1,000 = 10,519.2kWH per year saved

10,519.2kWh x $0.11 = $1,157.112 saved per year

May 8th, 2012 at 1:41 PM

What is the cost savings. I power washed the coils on my AHUs.I dropped 5 amps off of each phase.480volt unit. What is my cost savings over the year if they run for 12 hours each day 365 days a year. My cost is .11cent per klh

January 31st, 2012 at 11:38 PM

Isaac,

You need a charge controller as well. I don’t have a diagram handy, but you want your positive (+) side of the solar panels connected to the positive (+) of the charge controller input, do the same with the negative (-). Now connect the charge controller battery side or output to your battery in the same manner, positive (+) to positive (+) and same with the negative (-). Then the battery gets connected to the inverter the same way. Then the inverter can have devices plugged into it directly, or you can wire it to your circuit breaker box to power a certain set of devices/outlets, or you can have it power entire home.

If you are connecting the inverter to the breaker box, install a separate breaker for the inverter with it’s own outlet. This way you can switch from power company to solar, or solar to power company. If used as a backup, you can turn off mains from power company then turn on breaker from inverter so your electricity doesn’t get passed through the lines to people working on the power lines.

January 31st, 2012 at 5:04 AM

pls i need help on connecting my solar panel with an inverte and batteries can u help me with diagram on how to connect it..pls i will be grateful . thanks

January 23rd, 2012 at 11:49 PM

Tom,

Is this a 76kw wind generator? Gas, solar, etc.? This will help me understand how long the generator will be running each day. Thanks!

January 22nd, 2012 at 1:16 AM

How many average 2,000 Sq Ft homes in the northeast would a 76 KW generator be able to power? Assume no central air, and oil fired furnaces (no electric heat).

Thank you.

November 6th, 2011 at 10:42 AM

Ram,

Sorry I don’t understand your question. Not sure what 200 units means. 200 hours?

November 4th, 2011 at 12:36 PM

hello..if load is 500 watt,monthly consumption is 200 units ,so how can i calculate the kwh?

June 9th, 2011 at 7:53 PM

Jean-Marc,

A computer power supply pulling 50amps!?!? That can’t be correct. 120V x 50amps = 6,000watts.. Most likely the 50amps is on the 12v side of the power supply 12v x 50a = 600 watts. Which seems more likely. The power supply will probably say 600watts on it. With a 600watt pull that would be 600watt / 120volt = 5amp. So your computer power supply will be pulling 5amp.

May 29th, 2011 at 10:40 PM

hello there i am loking for buying a new power supply for my computer, and i got a little question about it

it says on the information, that the power supply can generate up to 50 amps of power, my question is, i live in an appartement and my electric box uses fuses, i got a 20 amp fuse and a 25 fuse, my question is, does a power supply convert volts into amp or smthing or will it take raw amp and make my buse break all the time?

May 19th, 2011 at 7:52 PM

Kenny,

This depends on if the amp meter is running after the voltage is 120VAC or if its before the inverter on the 6VDC battery side. Im going to assume it is after the inverter on the 120VAC side.

5amp x 120V = 600watts

6amp x 120V = 720watts

So your constant pull is 600 – 720watts

With your AC or water heater on you are pulling

15amp x 120v = 1,800watts

17amp x 120v = 2,040watts

So you are pulling around 1,800 – 2,040watts when AC or water heater is running.

Hard for me to figure out the ac or water heater for cost as I don’t know how many hours they are running. As for the constant, I can help you there as it is 24 hours everyday.

I’ll use the 720watts for this calculation.

720watts x 24hours x 365.25days / 1000watts / 12months x $0.12 = $63.12 plus some companies may tack on an extra $10-$30 for “delivery” basically a charge to use their electric lines.

As for the water heater and AC you can use this formula to figure out how much the cost is per month instead of the formula above:

I’ll use the 17amp but yet subtracting the constant since we have that calculated already.

1,320watts x plug in hours per day here x 365.25days / 1000watts / 12months x $0.12 = cost per month with ac/water heater running, now add that to the constant $63.12

Hope that answers your question, have a great day and remember to visit often!

April 12th, 2011 at 11:30 AM

LOTS OF GREAT INFORMATION I NEED SOME HELP I LIVE IN A MOTORHOME AND TRAVEL ALL OVER I HAVE SOLAR PANNELS ON MY ROOF AND FOUR 6 VOLT BATTERIES IN STORAGE. MY QUESTION IS MY POWER METER READS IN AMPS. AND DURNING A NORMAL DAY I AM USING 5 TO 6 AMPS AS A CONTANT. IF I TURN ON THE WATER HEATER OR THE AC IT WILL JUMP TO15 TO 17 AMPS. WHAT I WANT TO KNOW IS HOW DO I CONVERT AMPS TO WATTS SO I CAN GET A FAIR IDEA OF HOW MUCH POWER I AM USING AND WHAT IT COSTS IF I HAVE TO BUY IT FROM A SOURCE AT SAY 12 CENTS PER KWH

THANKS FOR YOUR HELP

KENNY

March 20th, 2011 at 12:18 AM

Anita,

I would need the PF (Power Factor) to be able to do any calculations for you. The standard/average is a PF of 60% or 0.60, but this is not always the case. Depends on the generator, transformer, etc. whatever your appliance is. You may be able to find this info on the unit’s power ratings. If you can get me that information I’d be happy to help you out. Thanks and have a great day!

March 11th, 2011 at 12:09 PM

Hi, I have an appliance in my shop that is 7.5Kva. Can you tell how to measure the power consumption per hour for this,thanks

February 15th, 2011 at 7:50 PM

36,000 sq. meters producing 10 watts each sq meter = 36,000 x 10 = 360,000 watts

(360,000 watts x (8 hrs each day x 365.25 days a year)) / 1,000 = 1,051,920 kwh per year ($115,711.20/year)

1,051,920 kwh / 12 = 87,660kwh per month ($9,642.60/mo. based on $0.11 / kwh)

hope this helps, let me know if you need any other help.

February 15th, 2011 at 4:38 PM

I have 36,000 sq. meters of area that can produce 10 watts per sq. meter for min of 8 hours a day.

how much savings based at 11 cents a kwh.

could you help me with some KWH per day costs, savings, etc.

January 2nd, 2011 at 2:51 AM

What is the voltage? I need the voltage of the 90 amps to convert it to watts.

December 28th, 2010 at 5:25 PM

how much would it cost to run 90 amp electric heater for 24 hour @12 cents a kwat hr thank you

August 8th, 2010 at 11:06 AM

Well most solar panels I’ve seen go by wattage, not amperage. Is this 1550kWh per year? per month? per day? Are you going to run directly from solar panels or are you going to have batteries charging as well? These are things that need to be know to be able to figure out what type of solar panels are needed, and how many.

July 30th, 2010 at 7:09 PM

Sorry, I still need help. I want to go to solar backup. How do I convert my current average of 1550 kwh to amps so I can choose the correct ampage on a solar panel.

September 25th, 2009 at 8:00 AM

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