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Hughes Autoformer: Shield Your RV From Low Voltage Shore Power

Hughes Autoformer: Shield Your RV From Low Voltage Shore Power

In over 20 years of full-time RVing, we can’t begin to count the number of times we’ve hooked up at RV parks (even expensive high-end parks) and seen readings on our voltmeter that are way too low. Many years ago we learned about the Hughes Autoformer, and we haven’t had to worry about low voltage conditions damaging the expensive appliances and equipment on our RV since.

Low voltage can cause valuable electronic equipment to draw more amps, or current, which can lead to overheating and premature failure. RV low voltage problems can cause serious damage to expensive appliances like air conditioners, microwave ovens, washers & dryers, and (120V AC) residential refrigerators. It’s also harmful to the many components in our electrical cabinet including our RV internet solutions.

Our Hughes Autoformer solves the problem. In this post, we’ll show you why an RV autoformer has long been a critical piece of our RV gear.

What Does a Hughes Autoformer Do?

The word “autoformer” actually refers to an autotransformer, an RV power protection product that acts as an RV voltage regulator. An autoformer is a particular type of transformer that uses a non-isolated winding to step the available line voltage from a power pedestal up or down to match the load’s requirements.

So, if your RV is connected to a power pedestal that suffers a voltage drop and you run your RV air conditioner, for example, your AC unit could be damaged by that low voltage. Appliances with motors are most vulnerable to low voltage conditions, but any of your rig’s appliances or electronics (and your entire RV electrical system) could potentially suffer long-term damage from repeated/extended exposure to low voltage power.

A Hughes Autoformer will step up the line voltage to better match the requirements of your AC unit, protecting it.

A Hughes Autoformer

This is our 50-amp Hughes Autoformer. It’s also available in 30-amp size for 30-amp RVs.

Technically, an autoformer uses the voltage-amperage relationship defined by Watt’s law to boost the voltage supplied to your RV. This prevents damage to sensitive equipment and helps it operate more efficiently.

But there are two types of electrical loads: resistive and inductive. It’s important to note that autoformers help 100% with inductive loads. They do not draw more power but instead enable the device or electrical load to pull only its required amperage. However, they do actually result in more current being pulled (though for less time) for resistive loads.

So, for the sake of clarity, let’s look briefly at the difference between resistive and inductive electrical loads in RVs (it gets a bit technical, so bear with us).

Resistive Loads

A resistive load is a type of electrical load that converts electrical energy into heat or light. Resistive loads are simple loads where the sine waves of the current and voltage are in phase with each other, but there is simply resistance to the flow of current.

When the voltage supplied to a resistive load drops, the required input current doesn’t increase. But, the output power (watts) of the device/circuit will decrease, so the load will have to run longer to do the job.

An example of a resistive load in an RV would be the heating element in your water heater. If the input voltage decreases, the heating element doesn’t get as hot, so it has to run for a longer period of time to bring your water to temp.

Inductive Loads

An inductive load is a different type of electrical load where the incoming current is converted into a magnetic field. An opposing force (inductive reactance) resists any change to the current’s flow, causing the current in the powered circuit to lag behind the voltage.

Inductive loads are more complex loads where the current and voltage are out of phase, so a secondary voltage is created that moves in opposition to the supply voltage. This is why they tend to create power surges when turned on (a sudden inrush of current required to overcome the resistance to starting) or off.

Inductive loads include motors and magnetic coils (transformers). In an RV, the fan and compressor in the air conditioner(s) are examples of inductive loads, since they are both run by electric motors. Transformers are another inductive load that’s built into virtually all electronics since they’re used to convert the incoming power to different voltages.

The windings of wire in electrical motors and transformers create an inductive load.

The windings of wire in a motor or transformer, converting the flow of electricity into a magnetic field, create an inductive load.

Why Is It Important for RVers to Use an Autoformer?

A high-quality autoformer is a valuable piece of RV gear because low-voltage shore power can be found anywhere. The national electrical code standard is a range from 114-126 V. There are many campgrounds with power pedestals that are old and/or poorly maintained, and our voltmeter has frequently identified much lower voltage readings.

We’ve even found low-voltage issues at expensive high-end RV parks… which suggests that RV park power diagnostics may not be looked at very frequently. So, a low-voltage condition (or a condition that results in high voltage, which can be equally dangerous) can be found just about anywhere you connect your rig to power.

Moreover, low-voltage shore power is becoming more and more of a problem as RVs get larger and require more power (more A/C units, more electronics, etc). In addition, rising temps result in more people running their air conditioners to stay cool, so brownouts are becoming more and more common. (Brownouts are periods of reduced voltage in the electrical grid, sometimes intentional and sometimes as a result of excessive load.)

So, having a device that can help protect your RV’s expensive electronics and appliances is becoming an increasingly important issue. A Hughes Autoformer isn’t cheap when you make the purchase, but it sure turns out to be cheap insurance if it protects you from having to replace AC units, electronics, your microwave, etc.

Is an Autoformer the Same as a Surge Protector?

Absolutely not. An autoformer is not the same thing as a surge protector.

As we note in our full post on RV surge protectors, a surge protector offers protection from an electrical surge that can come through the power pedestal into which an RV is plugged. An electrical surge can damage RV electronics and appliances (both those that came with the RV and anything plugged into a 120V AC outlet). So, a good RV surge protector effectively manages and protects your electrical system.

A Power Watchdog surge protector

Here’s John with our surge protector, a Power Watchdog. We had it hardwired into our RV, but we no longer needed it once we had the Hughes Autoformer on board.

A high-quality RV surge protector has the ability to cut the power coming in from the power pedestal automatically when a dangerous electrical event occurs (like loose connections or a bad circuit breaker at the pedestal). A good surge protector also automatically restores power to the RV once power is detected as being safe and the electrical event is no longer a threat.

With a Hughes Autoformer, you don’t need an additional surge protector because this autoformer offers advanced surge protection in addition to being a voltage booster when a higher voltage is required. (Note that not all autoformers offer advanced surge protection, however, the Hughes products do.)

Before we knew about the Hughes Autoformer, we had hard-wired in a surge protector which we thought would offer adequate protection for our rig’s appliances, electronics, and electrical system. If we had to do it over again, we’d skip the separate surge protector entirely and simply hard-wire in a Hughes autoformer, which can replace a surge protector entirely. (Hard-wiring it in would have eliminated the need for a 50-amp extension cord for us.)

The bottom line is that even if your RV has a high-quality surge protection system, your rig is not protected from the low-voltage conditions found in many campgrounds and RV parks.

Operating with low voltage power could cause an electrical fire.

Repeated/excessive operation in low voltage conditions could lead to an electrical fire in your RV.

Do Autoformers Steal Power?

This is an understandable question and one we’ve often heard, but no – autoformers do not steal power. Many people think they do because autoformers generally aren’t very well understood. Let’s take a look at a quick example to clarify:

If you’re at a campground or RV park during a period of very hot weather when many RVers are running their air conditioners and there’s a voltage drop due to the high demand, you may find that some RVers are able to continue to run their A/C units while others are not.

What you’d be witnessing is RVs with autoformers being able to function normally because they are regulating (stepping up) the line voltage, and RVers who can’t run their A/C units due to the low voltage condition.

If you’re interested in more information and testing to show that using an autoformer isn’t stealing power, check out this YouTube video:

Remember – low voltage can damage your RV’s equipment over time. If you don’t carry a voltmeter with you in your RV, you should. If you see a voltage reading outside the national electrical code standard of 114-126 V, you’ve identified a condition that could result in damage to your appliances, electronics, or even your RV’s electrical system.

Again, low voltage isn’t good for any equipment, but the things most vulnerable to damage are devices with motors in them like air conditioners, microwave ovens, washers & dryers, and (120V AC) residential refrigerators. Low voltages cause these appliances to draw more amps (current), which can lead to overheating and premature failure. Smaller electronics can be damaged as well. For example, our computer power supplies get noticeably hotter when plugged into poor power… which will shorten their lifespan.

We’ve long protected our RV and everything on board by using a Hughes Autoformer. We simply plug the autoformer into the RV park’s power pedestal and plug our RV into the autoformer. This not only gives us a voltage boost but also surge and spike protection. We wouldn’t be without it.

To see our Hughes Autoformer in action under various conditions at several RV parks, we encourage you to take a look at our YouTube video on this topic:

And since we shot the above video, we’ve done an updated version, showing how we use our Hughes Autoformer in conjunction with a Hughes Power WatchDog (an advanced RV surge protector) for the ultimate electrical protection for our RV:


Which Hughes Autoformer Do I Need to Protect My RV?

Hughes makes autoformers for both 50-Amp RVs and for smaller 30-Amp rigs. Depending on the amperage of your RV, you’d want to order accordingly. Note that if you have a 50-Amp RV and you’re at an RV park or campground with a 30-Amp or 20-Amp power pedestal, you can use a dogbone adapter to connect your autoformer to 30-Amp or 20-Amp power. For more on dogbone adapters, see our post on plugging in an RV (Dogbones 101).

Hughes Autoformers are available directly through Hughes (with a discount available… see below):

Hughes also makes installation kits that allow the autoformer to be permanently mounted inside the RV. This offers both theft and weather protection. For more on this, see our YouTube video above.

If you choose to buy any of these products through Hughes, be sure to use our RVgeeks Hughes Autoformers Affiliate Coupon (10% off using coupon code RVGEEKS at checkout):

Hughes Autoformers Logo

Hughes 10% Discount



Make sure your RV is protected from low voltage, bad RV park wiring AND power surges when connecting to shore power with a Power Watchdog and/or Hughes Autoformer. We never hookup without ours (we have both), and know our RV's electrical system and all our electronics are being protected.

Watch our Hughes Autoformer video
Watch our Hughes Power Watchdog video

Save 10% on your entire purchase when ordering from Hughes!

SAVE 10%
Hughes Autoformers Logo
Hughes 10% Discount

Make sure your RV is protected from low voltage, bad RV park wiring AND power surges when connecting to shore power with a Power Watchdog and/or Hughes Autoformer. We never hookup without ours (we have both), and know our RV's electrical system...Show More

Make sure your RV is protected from low voltage, bad RV park wiring AND power surges when connecting to shore power with a Power Watchdog and/or Hughes Autoformer. We never hookup without ours (we have both), and know our RV's electrical system and all our electronics are being protected.

Watch our Hughes Autoformer video
Watch our Hughes Power Watchdog video

Save 10% on your entire purchase when ordering from Hughes!

Show Less

If you’d like to use Amazon to check out user reviews and/or to make a purchase (occasionally, prices on Amazon even beat the direct price with the discount):

Power Watchdog Hughes Autoformers RV 2130-SP, Voltage Booster with Surge Protection, 30 Amp
  • Fit type: Universal Fit
  • Fully automatic 10% voltage boost when needed, Boost indicator

Hughes Autoformers RV220-50-SP, Voltage Booster with Surge Protection, 50 Amp
  • 50 amp- 12,000 Watts Capacity, 4,800 Joules of Advanced Surge Protection Built-in with indicator light
  • Fully automatic 10 percentage voltage boost when needed, Boost indicator light when needed

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Sunday 12th of November 2023

The only time we ever needed an Autorformer, the park was apparently well aware of their voltage problems because they had several of these on hand to lend. It worked as advertised, and we bought one - at no small cost (in $$ or weight). We haven't used it once in two years, so hopefully the day that we do need it, the thing will work. The Autoformer is probably a "nice to have" for most, not a "must have" like a surge protector. Whether you're a full-timer or a part-timer, an Autoformer is definitely good insurance.


Monday 13th of November 2023

Thanks for sharing your experience, Bee. One point... the Autoformer can only do its job and provide you that protection and "insurance" from low voltage, a surge, etc... IF you have it plugged in. Keeping it in your bay for a future need is great... but a park's electrical system can have low voltage or a failure that can affect you at ANY point during your stay. Be careful out there! 😉


Sunday 12th of November 2023

Typical thorough explanation on voltage strength, and the ability of the Hughes Autoformer to help when power is both low, and to high too:)!

We too have been able to comfortable power our AC's at times when many around us were not able to do so.

Over the years, we've had two of the earlier generation Hughes that did not include the current generation Hughes Surge Protector. So those who are buying used units, be aware they do not have the Modularized Surge Protector unit on board.

For those with the newer units, that depend upon the Hughes Autoformer with Modularized Surge Protector to be and All-in-One pathway into their RV's - I recommend carrying a spare Modularized Surge Protector component. For those with the older units, or in our case even with the new Modularized Surge Protector - I recommend having a Stand Alone Surge Protector, first in line, as the power flows in.

Shore Power > Surge Protector (We had ours on board in the coach, with the Shore Power cord modified with a Female Plug for the Progressive Surge Protector to plug into. This way, if it Takes one for Team from a spike - we can bypass it by moving the plugs around.) > Hughes Autoformer (Also Male to Female plug, for more redundancy to bypass as needed.) > On into the coaches OEM Combo Surge/Automatic Transfer Switch > And on into the coaches 120V Circuit Board.

Please let me also share this story, power related too..

On this years travel, at Eagles Nest RV Resort in Polson, a 2019 Dutch Star 43' coach, ended up being salvaged from a lightening strike that hit the ground approximately 100 yards away. The gent did have a good quality Surge Protector at the Shore Power Pole... But, he had his Jacks Down, without Snap Pads or Wood/Rubber pads... The power of that lightening strike, worked it's way up and into the coach. Taking out many, many coach, and Freightliner, electronics components. I share this, because besides Low/High Power being an item to be aware of - Mother Nature has the ability to thrill us with her power. (We had unplugged from Shore Power, and were Air Leveling only. So were lucky we were not impacted a few others further away from the strike, lost some electronic items too - but that Dutch Star's (And it could have been ANY coach...) being knocked out so hard - was an eye opener.


Thanks for the as always, informative knowledge sharing. Travel safe, and best to you and all - Smitty

B. Hislop

Sunday 12th of November 2023

Virtually all electronics made in the last 20 years use small, light weight switching power supplies rather than transformer based. A switching power supply usually has a wide range input voltage for world-wide use and doesn't really care what the waveform looks like (have you looked at the output waveform of a small UPS?). Just checking two laptops here and both power supplies are rated 100-240VAC. My cellphone charger is 85-250VAC. Most newer RV power converter/chargers are also based on switching power supplies. Motor and transformer based devices are the ones most affected by low voltage.

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