Thursday, November 30, 2023


RVelectricity: Hughes Autoformer – A cure for low campground voltage?

By Mike Sokol

Dear Readers,

Not a week goes by without me receiving at least a few emails and questions about the Hughes Autoformer. This is advertised as a cure for low campground voltage, and its users are adamant about how great it works, and everyone else at the campground is shutting down while their own air conditioner is still working, etc.

Note that in the 2020 National Electrical Code any voltage boosting transformers have been made a violation of NFPA 1192, allowing campgrounds to force you to disconnect or leave. This is based on the premise that an Autoformer (or autotransformer) increases the amperage draw of your RV’s electrical system to make up for the lower voltage.

There’s nothing magical about the Hughes Autoformer since it’s basically an autotransformer with a voltage sensor and transfer relay. When the incoming voltage goes below a certain value, the relay kicks in adding a 10% voltage boost. I’ve been installing autotransformers (the manual version of this product is called a buck/boost transformer) in industrial buildings and churches for more than 40 years, and I know exactly how they work.

According to the NEC, these autotransformers increase the amperage load in a campground electrical grid because they draw 10% more amperage than the RV should be using. But according to Hughes, they actually help reduce overall amperage draw because air conditioner and refrigerator compressor motors tend to draw more current as the campground voltage gets lower.

According to me, I know that both of these statements are true to some extent, but I don’t know which one has the greater effect on campground power. Do RV air conditioners really draw more amperage as the voltage goes down? All my textbooks say so. Does the Hughes Autoformer have the ability to negate that extra amperage draw enough to make up for the extra amperage it uses to boost the voltage? Heck if I know for sure. I can run textbook calculations all day long, but it’s hard to know all the variables.

However, I do know one way to find out. I’ve just bought a 3kVa variable transformer (a VariAC) that can vary the line voltage from 0 to 140 volts. And my HRDL (High Speed Data Logger) meter can monitor both voltage and current going in and out of my VariAC with extreme accuracy. And while I’m at it, I’ll also do this experiment with both a SoftStartRV controller and the factory starting capacitor on a Dometic Penguin II 15KBTU air conditioner.

Finally, if Hughes will send me a 30-amp Autoformer to try out, I’ll be glad to put that in the circuit as well and share all my test data with them as well as you. Be be aware, this will be a warts-and-all review, so whether it works as Hughes says it does or not, I’m publishing either way. That’s my guiding principle.

Sadly, I have no budget for any of this so I’ll have to spend dozens of hours and hundreds of dollars to do this experiment. But I think it’s worth it in the long run to answer the Hughes Autoformer question for the RV industry once and for all.

Stay tuned for a real scientific study on this technology. See you then.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.




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Al Buckner (@guest_89917)
3 years ago

Mike, going back to a statement in the article “Note that in the 2020 National Electrical Code any voltage boosting transformers have been made a violation of NFPA 1192″… Is the updated code a broad statement or more refined… asking because aren’t all those large transformers all around the campground (installed by the power company) doing the same thing to regulate the campground power from the power company?

Al Buckner (@guest_90025)
3 years ago
Reply to  Mike Sokol

Thanks Mike, that is what I thought… just wanted experts confirmation.

Michael (@guest_89614)
3 years ago

I remember from my quite abbreviated career as a EE college student (I mean REALLY abbreviated) that electrical power is measured by multiplying voltage times amperage. Since a transformer only changes voltage, then power in equals power out (less any inefficiencies in the device). How a bunch of smart electrical guys didn’t know that implies someone might have had an ax to grind.

Sure it will promote more power consumption. When the voltage drops low enough, those of us with power protection will disconnect and sit there hot and dark. If we condition the electricity we’re paying for, we’ll use it.

Shame on Hughes if they made unrealistic claims. I guess you reap what you sow.

Drew (@guest_89556)
3 years ago

Just as an aside to this- I quit using the 30a. receptacle at the campground pedestal years ago. I use a 50 to 30a dog bone to use 1 leg of the 50 for my power. The design is superior to the 30a. and it should handle higher amperage better. In addition- one leg of the 50 is 50 amps, where the only hot of the 30 is just 30 (in a park where the 30a. receptacle is new or nearly new.)

Al Buckner (@guest_89911)
3 years ago
Reply to  Drew

Drew, I’ve actually ran into RV Parks that prohibit dog-bones on any kind… 30-to-50 or 50-to-30. Their real reason to ban both is because of the 30-to-50 that they claim you will be trying to pull 50amps out of a 30amp circuit and damaging their pedestal!

rsdata (@guest_89555)
3 years ago

“But fact is, many of them are in serious trouble trying to supply power through an antiquated power grid.”

Mike this is your comment and I agree 100%. I the last two weeks my local energy coop has limited ( thru electronic monitoring installed) my AC usage when it is really hot. The AC is turned off and back on automatically according to overall grid usage and health. Campgrounds I am sure are in the same boat.

Steve (@guest_87176)
3 years ago

So Mike, Reading you column and thanks it is great, Interested in the hard start cap test.

But with the Autoformer I have a question. If my voltage goes to say 100 vac and the Autoformer kicks in, I understand that the amps increase. W= VxA. So if I pull more amps, wouldn’t I be limited by the 50 amp breaker at the pedestal? So using that logic, If the campground is properly configured for power and 50 amp pedestals, you really should not overload the system. In theory, the system should not be affected, however I am sure most systems are not built for full 50 amp draw on a continuous basis. Interested in your thoughts!

TomS (@guest_86866)
3 years ago

Sounds to me that the campgrounds need to be brought up to code and the autotransformer wouldn’t be needed.

David Kendall (@guest_86779)
3 years ago

I look forward to your test results. Thanks for your research and dedication.

I suspect that our RV electric appliances have a shorter life from poor campground voltage. Wonder if a test could show if an AC run at 120 volts lasts longer than one run at 110.

Lynn (@guest_86552)
3 years ago

Plan A: Use your autoformer and have a good day.
Plan B: Have your A/C struggle, drawing serious amps, and burn out like the others.
Plan C: Sit in the dark and heat since your overpriced EMS shut you down.

Does anyone believe that a campground full of struggling, over-heating and damaged air conditioners is a safe thing?

Bob Berends (@guest_86438)
3 years ago

Mike, you are a rock star. Oh, wait a rock star equipment guru.

David (@guest_86617)
3 years ago
Reply to  Mike Sokol

Any pictures? It’s nice to read about another side of you, other than the RV electrical genius we’ve come to know you as! 😜

Fred (@guest_86433)
3 years ago

I’ve had a 50 amp Huges transformer for the last 5 years of our fulltiming & it’s the most wonderful piece of equipment I’ve added, along with my air conditioner Soft Start module. We’ve been in so many parks where the voltage drops well below 110V when the air is running, especially when the parks are full on a hot day. The transformer does a wonderful job of bringing the voltage back up to an acceptable level. My 5th wheel set up allows me to have the transformer inside my basement, near the electrical plug in point of the rv, so no one knows I am using a transformer.

David (@guest_86618)
3 years ago
Reply to  Fred

I’m right there with ya, Fred. I was able to shoehorn mine in next to my cord reel so it’s never seen. It will be interesting to read what Mike comes up with, however.

Al Buckner (@guest_89914)
3 years ago
Reply to  Fred

Fred, after encountering several neighbors at several campgrounds complaining to me that my (visible next to the pedestal) Hughes was stealing their power… I did some rewiring inside my electrical bay and just installed the Hughes in there (out of sight
). Just looks like a 50amp cord coming out of the RV directly to the pedestal… No More Complaints for the last 3 years!

Last edited 3 years ago by Al Buckner
David Kendall (@guest_86418)
3 years ago

If you’re paying for 30 or 50 AMPS, you can legally use it. Are we going down the road of banning things because campgrounds have outdated electrical systems? Thanks to Mike, I began monitoring campground voltage last Winter. My wife said it nearly ruined our camping because I saw how terrible campground voltage was and was reluctant to turn on the AC. Prior to being “educated “, I was dumb and happy and ran AC as much as we wanted.

Mike (@guest_86380)
3 years ago

There is a breaker on the pedestal, anything that doesn’t trip it should be legal.

Ralph Williamson (@guest_86351)
3 years ago

Obviously anything plugged into a 30A or 50A circuit breaker is not going to draw more than 30A or 50A, except for a very short duration. So I don’t understand the argument against them.

Last edited 3 years ago by Ralph Williamson
mike henrich (@guest_86321)
3 years ago

The first time I used my Hughes at a campground was last weekend. I tried it at home but it never went into boost mode. So at the campground, while I was working at the picnic table, I had a multi meter plugged in next to me. I could hear the AC get louder and seem to slow down. I looked at the meter, and watched the voltage drop. As soon as the voltage hit 112, it jumped to 120. I could hear the AC run normal as it was breathing a sigh of relief as it wasn’t struggling anymore. For me, if it will extend the life of my RV components, it’s worth it. Next time out I’m taking my ammeter with. I’m also going to be trying something else. I ordered a 50 amp dog bone adapter with 2-30 amp outlets. I plan on seeing if 1 leg has a higher voltage, I plan on plugging into that one which should help the campground situation. Unless the installer took time to split the 30 amp legs from site to site, 1 side of the 50 amp should have higher voltage.

mike henrich (@guest_86869)
3 years ago
Reply to  Mike Sokol

Yes exactly what I meant. reversing legs from pedestal to pedestal would split the loads, so to speak. But, when most of these systems were put in, who would think it would be an issue.

Allen Gayken (@guest_89652)
3 years ago
Reply to  Mike Sokol

I do it throughout our park and it make a big difference.

Mojo (@guest_89862)
3 years ago
Reply to  Mike Sokol

Alternated the feeds 35 years ago to help balance the loads. Problem is that most of us never envisioned three air conditioners, electric water heaters, electric unit heaters, washers and dryers, electric frying pans, electric hair dryers drawing 15 amps, etc., etc. now being included in RV’s. Makes it cheaper for the manufacturer to build but much more expensive for a campground to meet these requirements. Campgrounds that properly meet these requirements will need to fairly charge to meet these demands.

Dave (@guest_86288)
3 years ago

I’ve never understood the campground’s concern with autotransformers. If it is plugged into 30 amp service at the pedestal then it isn’t going to draw more than 30 amps no matter how hard it tries to offset the low voltage condition. If the campground’s electrical infrastructure can’t handle the rated amperage that would seem to be their problem.

J J (@guest_86444)
3 years ago
Reply to  Dave

Three RV’s are having electrical problems but one is not and it has an Autoformer sitting at the pedestal. Clearly, that RV is stealing power from the other three and causing the complaints and the problems. (insert “rolls eyes” emoji here)

It’s a lot easier and cheaper for a campground owner to deflect blame away from themselves than to correct the problem. Because if everyone is having problems, it must be the electric company’s fault, right? (insert “rolls eyes” emoji here)

That’s why mine is mounted inside the electrical bay. Out of sight, out of mind, and when people say they’re having electrical problems I just nod my head and say nothing.

To be fair, the National Electric Code, which is neither “national” or a “code”, does not require that 100% of the pedestal rating be available to 100% of the sites and 100% of the time. I think the current requirement is 80% capacity because they understand that no one runs at 100% capacity on their entire system.

Drew (@guest_86862)
3 years ago
Reply to  Mike Sokol


I can’t wait for your review! This week during days with temps in the 100 degree range, voltage inside my rig averaged from 108 down to 98 volts during peak usage hours. My ems shut down the rv at 102 but by then I shut off both ac’s and other big loads…then sat outside in the shade. My rv got to 90 degrees inside and I wasn’t able to use my ac’s until around 8pm when voltage stopped sagging and returned to a range around 110 volts. Please, please do this review asap- I want to be able to use an Autoformer- or a competing product.

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