The Don Rowe Blog

Jun 28

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Power Inverters and Air conditioners

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I get a lot of questions about running an air conditioner on a power inverter. The air conditioner is one of the hardest household appliances to run off of an inverter. The first thing to do when getting ready to run an air conditioner on an inverter is to get all of the specifications for the AC unit. The most important spec that you will need is the LRA rating. What this stands for is locked rotor amps. The LRA rating is what the AC unit will draw from the inverter while the compressor starts up. This is a very important spec when sizing an inverter for use with an AC unit. After you get this spec you will multiply it by the voltage and this will be the startup wattage needed by the inverter.

For example if your LRA is 60.6 amps if you multiply this by 115 you will get roughly 7000 watts at start-up.

The next thing to take into consideration for a AC unit is battery bank size. The best batteries that we have found that work well with inverters are the 6 volt golf cart or solar batteries. These are more cost effective and on average have higher amp hour ratings then the traditional group 27 12 volt deep cycle batteries. The 6 volt batteries will be connected in series. This will double the voltage to 12 and keep the amp hour rating the same. The inverter will see this as one big 12 volt battery. Your average 6 volt battery is 220 amp hour and sells for approx. 65.00. and your average deep cycle 12 volt battery group 27 is 115 amp hour and sells for 130.00. So if you get two of the 6 volt batteries it is twice the size at 12 volt s and you pay just about the same amount . If you want any kind of run time with a air conditioner it will require a large battery bank. I would have to say a minimum of 4 6 volt batteries wired in series to get longer then an hour. One of your best sources for the 6 volt batteries is a golf course. Reason for this is because the golf courses will really only use the battery for 6-9 months before getting rid of them.

Your next step in setting up a system for use with an AC unit is finding a sufficient recharge source for the batteries. You will want to have a minimum of a 150 amp alternator to recharge a system with a small AC. There are also many other options avaiable such as solar, wind or hydro.

This will get you started. I will post more about air conditioners and inverters as the questions come in.

20 Responses to “Power Inverters and Air conditioners”

  1. Texas_Bill says:

    Great BLOG! I have spent the past couple of years on and off trying to learn about all of this stuff. Perhaps you could post some information about the difference between stand alone inverters and utility intertie inverters. One of my current projects is to learn the electronics behind how the intertie inverters synchronize phase and voltage with the utility. For everyone out there, do NOT connect your inverter to your house breaker box unless it is designed for this purpose. There are multiple hazards that could result from this, including electrocution of a line worker who does not know that, even though utility power is off, your inverter is energizing the utility line. Thanks again for this resource, and I will post more later, with your consent.


  2. hojo says:

    I’ve been looking at buying a large power inverter that would let me temporarily run an AC unit or microwave on my RV using my truck.

    Inverter specs:
    Motor Trend (Model MT2400)
    2400 Watt-4800 Watt Power Inverter
    (2400 watts continuous power, 4800 watts peak)power
    Provides 20.86 Amps (AC)

    Air conditioner specs:
    I dont have the exact specs but I believe the thing probably uses 1200 watt / 10 amp VAC. The surge draw is probably about 4500 watts I am guessing. So I believe that equates to 100 amp VDC at 12 volts continuous power.

    The alternator in my 03 Chevy Avalanche puts out 145 amps.

    Is there any problem running the air conditioner or microwave of equivalent amp draw using this power inverter on my truck for indefinite period of time? Will it handle the initial surge OK?

    Do you recommend a smaller or larger inverter, or is this one sized appropriately?

  3. jon says:

    Texas Bill…I will see what i can do about getting some info posted on some intertie inverters for you. Thanks for reading my blog.

  4. jon says:

    Hojo…The Motor trend 2400 may be a little small for your AC unit. The surge time on the Motor trend 2400 is about 500ms. This may not be long enough for the AC unit you have. The best thing to do to get accurate specs. is to call the manufacturer and ask them what the LRA (locked rotor amps) are for the AC unit and how long it will surge for. Please post what you find out and the AC manufacturer and model number. Thanks

  5. Anonymous says:

    I was curious on how I could use solar power considering I live in sunshine Arizona I thought this could be of some benifite! I plan on running two freezers on a ice cream truck. I want to buy the biggest inverter because I do plan on hooking more things up ps2,monitor, and hopefully ac. Any help would be greatly appreciated. Sorry don’t know much about all this but willing to the truck is a 16′ panel van

  6. MR Pagan says:

    Mr Don , I need A Trace DR 3624 Power Inverter Owner Manual. My Inverter Was Bay in 1999 Tanks very much for Your help,

  7. Anonymous says:

    Ijust purchased and connected a 2500/5000 Vector inverter with 6ft of 2/0 cable as recommended to my 2005 F350 with dual 750 amp batteries. This setup will run a hairdrier, a curling iron, plus a 7.5 inch portable saw simultaneously, but will not run my average sized refrigerator which starts at 7.5 amps on house current.
    Any ideas as to the problem?

  8. Anonymous says:

    I ran my 20 cubic foot frige off my 1000 watt inverter with two 12 volt car batteries during the 2004 hurricane season. It was tricky, and had to advance the timer in the frige past the defrost cycle, with operates a heating element during this cycle, which the inverter was not able to run. Also unscrewed the light bulbs, as this put an added drain on the system too.

  9. Anonymous says:

    I ran a 5000BTU window A/C unit from my Xantrex 1000watt cont. Inverter,connected to 6 12volt,88 AH gel cell batts wired in parrellDuring Katrina.
    The A/C unit listed 5 amps on the tag.
    ran for a few hours with no problems.
    Now I have an old A/c that pulls 7.5 amps,& I don’t think it will run it(Used the generator to tun that one)
    I think the key is a NEW A/C ,with a ROTARY compressor.These seem to have the lowest LRA.

  10. Anonymous says:

    Hi, this is a great BLOG…I have a 2500/5000 watt Gorilla inverter…any info on the surge time on this and what you’ve heard about it’s reliabilty, etc?


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  12. Anonymous says:

    I have a toyota Prius. What is the largest Inverter load can I handle. Can I run a small AC? I have a large deep cycle battery I plan to put in the system.

  13. william Serge says:

    I have aquired 9 1300 watt invertors, and want to get them in line for a grid tie system. These are commercial rated froma cell site..
    What battery bank amperage size would I need, and woulda wind turbine 500 watt wind generator be amle source, along with a few panels. what size (watts) [panels) should I buy? also combined with the generator (wind be enough to run my home grid tie?

  14. Anonymous says:

    I have a problem. i’m tryin to run a AC in my semi truck. I have a 2000 watts inverter an it just shuts off on me. all connections are good. I dont know what to do anymore. the AC output is 980 watts and 8.2 amps

  15. Jon Hardwick says:

    Your batteries and/or the inverter may not be large enough to handle the locked rotor amps that the AC requires for start-up. I would suggest calling the manufacturer of the AC unit and asking them what the LRA rating is. Let me know if you have any questions, thanks.


  16. Rain says:

    It’s really true that having an air conditioning unit at home will cost high on our electric bills. And that’s what I’m experiencing right now, since I installed an a/c unit in my room, I got high bills on electricity but still I have to accept it because I installed it to comfort me when I’m warmed.

  17. asamerkley12 says:

    Perhaps heat, air conditioning, cable tv and wifi in the garage seem a little excessive, but we have a good reason for making our garage nicer than our house.
    heating and air conditioning san antonio

  18. Anonymous says:

    I have a Coleman 3000 watt inverter and I need a remote for it?
    It has a three pin screw on plug.

  19. Anonymous says:

    want to install an inverter to run a window unit.all window units i can find are digital readout/control.will this work with modified sine wave inverter.true sine wave inverters are high dollar.

  20. Swati Pathak says:

    Air Condition normally takes 2200 Watt, so its hard to run them at normal inverter. But many brands(like: Su-kam, Exide, Amaron, Prestolite etc.) are launching there power backups so that they can also run AC very easily.