Friday, December 9, 2022


SoftStartRV – Run an air conditioner with a small generator


By Dave Helgeson

Camping high in the Blue Mountains

Earlier this year I installed a SoftStartRV™ on my RV’s roof air conditioner.

You can read about the installation and my first impressions here. Impressively, the SoftStartRV™ allows me to run an air conditioner with a small generator. It does so by significantly reducing the power requirements at startup.

My 2,200-watt Honda generator running in ECO (Economy) mode was able to supply ample power to start a 13,500-BTU air conditioner while also powering the refrigerator (on AC) and the power converter in the RV.

I also promised a follow-up report after I had the opportunity to field test the unit over the summer under varying conditions. My main point of interest was could I still run an air conditioner with a small generator at higher altitudes? As RVers, most all of us have experienced reduction in power (3% for every thousand feet of altitude gained) as we have driven our RVs over high mountain passes. This is due to less air available to support combustion in our engines.

The same principle applies to fossil fuel-powered generators. While my generator easily powered the air conditioner with a SoftStartRV at my home, which is very near sea level, it might struggle or be unable to in higher elevation settings like the mountains.


Fortunately for testing the SoftStartRV there was a hot spell while dry camping at just over 5,000 feet in the mountains. This was a great opportunity to run an air conditioner with a small generator that is now generating approximately 15% less power (5 x 3%).

Here is what I experienced: I started the generator on ECO mode like I had been doing all summer at lower elevations. The generator started the air conditioner with considerable effort and went into “overload” in less than 5 minutes of operation. Then I turned the ECO mode off and restarted the generator. While it ran longer than 5 minutes, it was soon in “overload” mode once again. Finally, I switched the RV refrigerator from “Auto” to “LP Gas,” which prevented it from running on electricity (120 volts) supplied by the generator without any further overload incidents.

Let’s take a look at what was going on

The 2,200-watt Honda generator with a maximum output of 2,200 surge watts and 1,800 rated watts at sea level was reduced to approximately 1,870 watts surge and 1,530 (85% of 1,800) watts rated at the altitude of 5,000 feet.

Using Ohm’s law we can determine 1,530 rated watts works out to a mere 12.75 amps of constant power. If you will review the “SoftStartRV Video” from my earlier entry you will see my RV drew up to 12.9 amps once the air conditioner compressor had been started. This is slightly more than the 12.75 amps expected in the approximation* above.

Therefore, in the first two attempts, the generator was just able to power the  air conditioner. When the refrigerator then most likely called for cooling it activated the 120-volt heating element (1.2 amp draw). This additional draw increased the load to approximately 14.1 amps, which was just too much for the generator.

No need for a big noisy generator with a SoftStartRV

If you are looking to run an air conditioner with a small generator, here are some things to consider

  • Power requirements will vary with the size and make of the air conditioner and RV.
  • Some generators may be more efficient than others when it comes to operating at higher altitudes.
  • Take into account other 120-volt power draws within the RV such as the converter / charger, refrigerator, etc. Then decide if those loads can be eliminated when operating the air conditioner via the generator.
  • Keep in mind the temperature drops three degrees for every 1,000 feet of altitude gained. Therefore, as your generator loses the ability to power your SoftStartRV-equipped air conditioner at higher elevations, it also becomes less likely you will need to operate your air conditioner. Example: It is unlikely you would ever need air conditioning when camping at 9,500 feet in the Big Horn Mountains of Wyoming.
  • If you RV solely at lower elevations like the southeastern United States, you can likely get by with a 2,000-watt generator.

Where does all this leave RVers that want run an air conditioner with a small generator?

If you dry camp often and don’t want to lug around a 3,000-watt generator or run two smaller generators in tandem, a SoftStartRV unit installed on your RV’s air conditioner is a GREAT alternative. It performs as advertised – you just need to understand the limitations of your smaller generator.

For me it’s been a game changer and I highly recommend the product.

Click here to receive a special discount and 90 Days Risk Free Trial on SoftStartRV for your RV’s air conditioner.

*Assumes that the generator is sized exactly to its engine’s size and loss of power at higher altitudes is proportional.


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Tommy Molnar
9 months ago

We live at about 5,000 feet. My Champion 2000 watt generator will run the A/C with the soft-start but it won’t do it from the Econ mode. It has to be on full bore power.

Tom M
9 months ago

I have a 2000 watt Honda and a soft start installed on my trailer. At 800 ft elevation it works fine at 2800 ft. it goes into overload. I would suggest nothing under a 2200 watt generator. I had the honda before the trailer so will be looking to upsize.

Mike Sokol(@mike)
2 years ago

In case anyone’s interested, here’s a video I made last month showing how to install a SoftStartRV unit on a Dometic Penguin II air conditioner. Should take you less than an hour to do, as long as you’re careful up on the roof of your RV. For many senior citizens I recommend that you find a local RV repair shop that can do the job.

2 years ago

Great article and very informative. My question is where do I find someone to install the Soft Start unit? I bought 2 for my Coleman Mach A/C units but no local RV shop will install them and I’m too old to crawl on the roof to do it myself.

Tommy Molnar
2 years ago
Reply to  Cal

I had a mobile RV repair guy install mine. Do you have any mobile guys around you? SoftStart has many installation videos on their site for various a/c brands and models.

Chuck Woodbury(@chuck)
2 years ago
Reply to  Cal

Cal, it’s pretty easy, I’m told. You can actually connect via your smart phone with a tech who will take you through the process as you are on your roof doing the installation.

Jack Hall
2 years ago
Reply to  Cal

Where are you? There is a guy named Darin (SP?) In the Washington/Oregon area who does mobile RV repair. He has done several youtube videos. His channel is something like “Happy RV”. He even has a video on the SoftStart.

Walt Howard
2 years ago

Dave! Well written! Very good piece! FYI We live in the NC Mountains (Beech Mountain, 4600 feet, 1st floor condo) in the summer and the OAT never gets above 79. We have ceiling fans and leave doors & windows open. Beech Mountain Golf Club advertises a free round of golf if you’re golfing and it gets above 79!

Mike Sokol
2 years ago

Dave, great writeup! This tracks closely with my own lab results testing the SoftStartRV controller.

Dave Helgeson
2 years ago
Reply to  Mike Sokol

Mike, Thanks! It’s good to know we are seeing the same results.

Jesse Crouse
9 months ago
Reply to  Dave Helgeson

I got the same results on a 95 degree day and when I ran 2 Honda 2000’s companioned together I could start and run 2 15kw Coleman heat pumps with no problems.

harold smith
2 years ago

At 9000′ elevation my sons Onan 5.5kw gas generator would not start. It had an adjustment on the carburetor that would go up to 5000′, but that was not enough. Talking to local RV repair shops, they say it’s a very common complaint up there. My Onan 12.5kw diesel generator had no problems when I exercised it a few times with a moderate load.

Tommy Molnar
2 years ago

I installed the SoftStart in our a/c on our TT. We live at 5,000 feet so big increases in altitude are rare. I have two Champion 2,000 watters which we could hook up in tandem for powering our a/c – if we needed to. Too much added weight, and too much lost space. Enter the SoftStart. Works as advertised. We can run our a/c easily with only one of our generators. However, if the generator is set to “eco” before the a/c is turned on, it will simply die. If the generator is NOT in “eco”, it easily starts and runs the a/c.

Last edited 2 years ago by Tommy Molnar
Dave Helgeson
2 years ago
Reply to  Tommy Molnar

Tommy, Good to know you are experiencing similar results at higher altitudes. Totally agree with your “Too much added weight, and too much lost space” comment.