Calculator  DC to AC amperage conversion run through an Inverter
So, you’ve got an electrical appliance to run, but no place to plug it in. When you need to run a regular household electrical type device in an area where no regular grid power is available, this calculator will help you figure out what size batteries and inverter you need!
Welcome to our DC/AC conversion tool (with inverter). This calculator is designed to assist you with power usage amounts, when converting from one power form to another using a DC to AC inverter. Just enter power numbers in the fields below, and we will do the calculations for you, including typical inefficiencies and all that other techie type stuff you may not care to calculate. If you are not sure of your numbers, have a look at the walkthrough illustrations below when entering numbers.
Enter AC Device Ratings
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Zuki
October 31, 2012 a 2:47 pm
The calculator uses Ohm‘s Law. Watts = Volts x Amps. We additionally take into consideration an average inefficiency rate of 15% because the power is passing through an inverter. Once you find the watt amount from the AC volts x amps, you can divide the watts by DC volts to get DC amps, plus 15%. Without the efficiency loss, AC or DC watts will always be the same because it is total power. But as voltage goes up or down, in order to have the same power the amps will adjust accordingly.
Tech
October 31, 2012 a 3:09 pm
Very useful. But I believe Watts = Volts x Amps is Watts law. Not Ohms law.
Dave
May 19, 2014 a 2:12 pm
Dave, that is correct. Thanks for the correction. Ohm’s law is V=I*R, Watt’s law is W=V*I, where V=voltage, I= current, R= Resistance, W= Wattage.
Tech
May 21, 2014 a 12:48 pm




Nice tool!
Thanks
Good idea to add the % of losses too!Thanos
November 24, 2012 a 4:30 am 
Nice tool
ThanksRam
November 28, 2012 a 8:20 am 
When talking about current, for example if a device is drawing 3 amps, does that mean 3amps per hour?
So if your drawing 3 amps from a 3amp/hour battery, that battery would last about 1 hour? Right?Tim
February 4, 2013 a 12:04 pm
Yes, power ratings are usually rated hourly. No, a 3 Amp Hour battery will not give you 1 hour of runtime at a 3 amp draw. For an explanation why, please read our article about Peukert‘s Law and Battery Capacity.
/kb/tools/peukertslawanerdsattempttoexplainbatterycapacity.html
Tech
February 5, 2013 a 9:37 am


VERY NICE TOOL.
RAJAVARDHANA NAIDU.G
February 27, 2013 a 2:50 am 
nice tool thanks for your information .can you explain about %loss calculation
Gops
March 19, 2013 a 3:43 am
The loss figured is based upon the average efficiency for Pure Sine Wave power inverters. In this case, 15% loss, or 85% efficiency.
Jeremy Fear
March 19, 2013 a 10:31 am


DC to AC amperage conversion run through an Inverter.
What is the correct explanation of why requires 5 DC amps per each AC amp?Hector
April 4, 2013 a 7:11 am
Amperage is the flow of electricity, while voltage is the pressure. Saying that it requires 5amps DC to 1 amp AC is not a correct statement. What is true is that in a 13volt (12 volt nominal) DC system, ran through an inverter that is about 80% efficient, the total power useage is approximently 78 watts, which would be a little under 1 amp at 115VAC. Wattage is the total power, which is comprised of voltage * amperage. If you change the voltage, but leave the wattage (total power) the same, then the amperage has to change as well.
Jeremy Fear
April 4, 2013 a 9:21 am


Ok I used your tool above (THANK YOU SO MUCH FOR THIS TOOL) to determine the battery I will require to run my 5V 2A device from a 12volt battery. The tool returned .92amp DC. So my question is how can I now determine what size battery in amp hours I require to run this device for 10 hours?
Shelly
April 11, 2013 a 9:05 am
www.batterystuff.com/kb/tools/calculatorsizingabatterytoaload.html
Jeremy Fear
April 12, 2013 a 7:49 am


Would this calculator also work if I wanted to know what a switch that was rated AC would handle in DC?
Jordan
June 17, 2013 a 11:36 am
Jordan, this calculator is a simple AC to DC conversion. It will not work for your situation. Thanks
Tech
May 21, 2014 a 12:35 pm


i wish to power a series of appliances whose total sum of wattage is 720 watts for a minimum of 3 hrs non stop. i have already purchased a 12v – 220v inverter which is rated 1500watts…my questions aer: what rating of one 12v battery (or a system of combined batteries) do i need to achieve this target.Also , what specification of solar panel charging system can charge the battery in a very short time like 2 hours of sunlight…we do have intense sunlight in my region.
thanks
John
May 26, 2014 a 6:41 am
Please email your question to tech@batterystuff.com
Admin
May 27, 2014 a 9:45 am


Hi tbere i am looking to no how long my 240 appliances will last for with 2 110 batteries working of a 1500watt inverter drawing 980watts in total a total of 88 odd amps of dc how long will my batteries last and what size of solar panel would suit to maintain my batteries as i have only a splitt relay wired as a charging system
Jonathan Burns
June 17, 2014 a 9:01 pm
240VAC doesn’t change the total power of the system. The same calculations will work. In your case, you will get roughly an hour 1/2 of run time.
Tech
June 20, 2014 a 11:55 am


I have a 24VDC power bay with a DC to DC convertor (48VDC). If I’m reading 30amps on 48VDC side how much power is my 24VDC bay actually providing?
Mike
June 23, 2014 a 2:52 pm
That depends on the efficiency of the converter. On the 48 volt side, you are using essentially 1450 watts. The wattage on the other side, the 24v side, will depend on the efficiency of the conversion process.
Tech
June 25, 2014 a 9:05 am


This is GREAT stuff.
Thank you ALL for the info.Bill Mertz
August 12, 2014 a 10:07 pm 
Good morning.
I have calculated that I need 300 Amps DC per day.
How many 250 watt 12 volt solar panels do I need to keep up with this demand.
My battery bank is 3000Ahs 12 volts.
Regards
BillBill Mertz
August 13, 2014 a 11:30 am 
Due to the fact that we don’t have all the information for your system we would need you to contact us at tech@batterystuff.com so that we can ask the appropriate questions, to get you the answer that you may need.
Admin
August 15, 2014 a 2:25 pm 
hi,
why do we hav some devices taking negative voltage?
e.g BTS operates in 48V (DC)Najm
August 21, 2014 a 5:14 am 
Either the multimeter is hooked up backwards, or you have forced the batteries to charge backwards. Usually you are reading the reverse terminals.
Tech
August 22, 2014 a 9:45 am 
Thanks, this was very helpful, but mainly to give me an idea of the current draw on the batteries so that I can work out what circuit breaker/fuse to get.
Sambo
August 26, 2014 a 4:13 am 
Great tool.
If you add inverter efficency as an optional input that might be good as well.
Fizi
September 6, 2014 a 4:51 am
Glad to help! I will send your recommendation up the food chain and see if we can make it happen!
Tech
September 12, 2014 a 1:07 pm


I have a portable 5000 BTU air conditioner unit. The tag shows that it uses 504 watts and 4.5 to 4.8 Amps. It runs very well with a 1200 watt generator. How long can it run using an inverter, a 100 amp hour AGM battery rated at 1200 watts?
Ron
September 11, 2014 a 9:19 am
504 watts / 4.8 Amps = 105 VAC. This would pull 46.37 Amps DC, so you could run about an hour before you start to excessively discharge the battery.
TECH
September 25, 2014 a 10:18 am


Can I use this in reverse? I have a 100A 240V sevvice but need to power a DC rectifier shelf that is capable of 200A. If I use this calculator and input 100A AC, 240VAC, 48VDC then the calculator shows 552A DC. DOes this mean that the 100A AC service can supply up to 552A DC?
Jason
October 31, 2014 a 11:53 am
In reverse it would be a charger vs an inverter, however if the charger runs off 240VAC and draws a 100A then it will put out approximately 552A on a 48V system, but it might vary depending on the efficiency of the charger.
Tech
November 19, 2014 a 10:23 am

This was exactly what I was looking for. I would like to have the formula though just in case I need to do it the old fashioned way.