What size generator do I need to power an RV?

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Stainless steel refrigerators, microwave ovens, and air conditioners (ACs); modern recreational vehicles (RVs) are truly home away from home. In fact, some of the large and luxurious RVs feature RV generators that are more powerful than the back-up power generator you might be using at your home. 

You might feel overwhelmed as you try to find the right size generator to power your RV. There are lots of options in the market and terminology around watts, amperages and volts. Meanwhile, there are simple methods you can use to narrow your options. In this article, you will find the answers to common generator sizing questions. If you are new to RV generators, check out RV generator basics for an intro.

What size generator do I need for my RV?

While the size of the generator you need depends on specific equipment you have within the RV, below is some high-level guidance. 

Generator sizes for different RVs
  • Class B Van with one AC unit: 2,000 to 3,600 watts
  • Class C RV with one AC unit: 2,800 to 4,000 watts
  • Class A RV with two AC units (15,000 BTU each): 5,500 to 8,000 watts
  • Class A RV with three AC units (15,000 BTU each): 10,000 to 12,500 watts
  • Fifth wheel with two AC units: 5,500 to 7,000 watts 

Please keep in mind, these ranges could change based on your specific equipment. 

Let’s take a more detailed look at the equipment within your RV, which will help identify the generator size you need. 

The first consideration is the electrical power needed by each appliance and device. Here is a list of common appliances and the amount of electricity they each need. 

Electricity consumed by RV appliances
  • AC units are often the appliance that requires the most power in an RV. AC units 13,500 to 15,000 BTU need between 1,200 and 2,400 watts of electricity to run. If you have multiple AC units, you can multiply the wattage needed accordingly.
  • Dishwasher: 1,200 to 2,400 watts 
  • Stove: 900 to 2,500 watts
  • Hair dryer: 1,200 to 1,875 watts
  • Clothes iron: 1,000 to 1,800 watts
  • Washer: 1,000 to 1,500 watts
  • Coffee maker: 900 to 1,200 watts 
  • Microwave: 750 to 1,500 watts 
  • Toaster: 800 to 1,400 watts 
  • Refrigerator: 400 to 1,000 watts
  • Blender: 450 to 700 watts 
  • TV: 43 to 600 watts 
  • Radio: 50 to 200 watts
  • Gaming console: 70 to 180 watts 
  • Laptop: 20 to 50 watts 

Please note that some appliances have large compressors and motors. These could require higher wattage when they start.

The second consideration is looking at the usage pattern for the appliances and devices. For example, you would likely not operate all these appliances at the same time. In addition, some appliances like refrigerators will run more frequently than others, like toasters. 

The final consideration is the difference between starting and running power. Some appliances need more power for a short time at the beginning of their operation. For example, AC units would draw much more power when they first start. 

What is the difference between 30-amp and 50-amp RV?

Let’s start with the basics. Electricity is simply the flow of electrons. You can read more about it in our article explaining the difference between electricity and energy. Amperage is the volume of electrons that flow, and a higher amperage means more electrons flowing and consequently more electricity. 

Thirty amp and 50-amp are the two most common electrical service capacities used within RVs. A 50-amp service can handle more electric power than a 30-amp service; this is because a 50-amp service can handle a higher volume of electrons. When you multiply amperage with voltage, you find the electrical power. Most electrical equipment in RVs operate at 120 volts, independent of 30-amp or 50-amp service. 

To find how many watts of power you have available, you need to multiply volts times amps. For example, a 30-amp RV with a 120 V electrical source would be capable of handling about 120 x 30 or 3,600 watts of electric power. 

What size generator do I need for a 30-amp RV?

An RV with a 30-amp shore power connection and with 120 V equipment would be capable of handling a maximum of about 3,600 watts of electric power. This means a 3,600-watt generator would give you the same amount of power as shore power. Meanwhile, you can also get a 4,000-watt generator for these coaches to give additional electrical motor-starting power. 

A 2,500-2,800-watt generator is often a good minimum threshold for 30-amp RVs that have AC units. 

What size generator do I need for a 50-amp RV?

An RV with a 50-amp shore power connection typically has two separate 50-amp feeds. This is different than a 30-amp RV with only one 30-amp feed. A 50-amp RV with a 120 V electrical feed is capable of handling 12,000 watts of electric power. This means a 12,000 or 12,500-watt generator could be your top end choice.

You can also get a better sense of the generator you need using the bullet points in the first section of this article, under “What size generator do I need for my RV” header.

Now that you have a better idea on the generator size you need, don’t forget to check how to find a quiet generator for your RV.

Get the most out of your RV! Sign-up below to receive periodic tips and insights any RVer would enjoy . 

Aytek Yuksel - Cummins Inc

Aytek Yuksel

Aytek Yuksel is the Content Marketing Leader for Cummins Inc., with a focus on Power Systems markets. Aytek joined the Company in 2008. Since then, he has worked in several marketing roles and now brings you the learnings from our key markets ranging from industrial to residential markets. Aytek lives in Minneapolis, Minnesota with his wife and two kids.

Cummins Custompaks are being used for water management as Thailand struggles with its water crisis

CustomPak on site

Water crisis

Sixty Cummins Inc. CustomPaks are in service in Thailand as part of a critical water management plan aimed at easing the country’s water crisis – a crisis that has caused enormous economic and social damage and stirred conflict among communities.

Over the past several decades, Thailand has continually faced water problems caused by severe drought. Water reserves in dams and reservoirs are insufficient while water resources are often contaminated with toxins caused by urban communities and the industrial and agricultural sectors.

Severe flooding is a threat, too, at a time when the realities of climate change are hanging over the country.

As a result, the allocation of precious water resources, which must be shared among various stakeholders including new and existing industry, large and small agriculture, and cities and villages has become a flashpoint.

Kittithanapat Engineering Co. (KTP), has been involved in the water management system since 1996, working closely with authorities such as the Royal Irrigation Department, Department of Water Resources, Bangkok Metropolitan Authority and others.

CustomPaks on site

600 hp CustomPaks

To help KTP meet its often urgent requirements, Cummins DKSH (Thailand) has recently supplied 60 Australian-built CustomPaks – 45 powered by Cummins’ X15 engine rated at 600 hp, and 15 powered by the QSL9 rated at 325 hp. These fully self-contained powerpacks are emissions certified to Tier 3.

The CustomPaks are coupled to hydraulically-driven, large-volume submersible water pumps sourced by KTP from US company Moving Water Industries (MWI); KTP is the exclusive distributor in Thailand for these MWI Hydroflo pumps.

Prior to Cummins’ involvement, KTP was using another diesel engine brand but service support wasn’t up to the standard required.

Long-serving KTP engineer Kittisak Thanasoot says Cummins DKSH’s reputation for technical and aftersales support along with the reliability of the Cummins product were a key reason behind KTP’s decision to specify the CustomPaks for the Royal Irrigation Department.

The ability of Cummins DKSH to respond to short delivery times was also important.

“Supplying large quantities of high horsepower diesel engines for emergency situations such as flash flooding can be a challenge for KTP,” says Kittisak Thanasoot.

“Responding to the needs of the government agencies to manage such problems in a timely manner and with least impact on communities, KTP has found the answer in our partnership with Cummins DKSH.”

Power, pride and passion

Parked semi truck

The switch back to Cummins power has been beneficial for iconic New Zealand company Uhlenberg Haulage. It's all about whole-of-life costs.

Uhlenberg Haulage is closing in on 60 years in business, having been founded in 1966 by Mike and Carol Uhlenberg.

Based in Eltham, Taranaki, in New Zealand’s North Island, the operation is today owned and operated by their sons Chris, Daryl and Tony Uhlenberg.

Describing the Uhlenbergs as “old school family truckies”, Daryl talks about the company’s time-honored journey with a definite tone of pride, especially the work of his parents in laying the foundations for what is today an iconic fleet in its own right.

Cummins Inc. made its debut in the Uhlenberg fleet in 1971 with an NH250 powering a second-hand Kenworth K923 used in logging. A second Kenworth, a new W924 with a Cummins NTC335, followed soon after hauling an LPG tanker.

The Uhlenberg operation today comprises 40 prime movers and a variety of trailing gear to cater for the myriad of a jobs the fleet is involved in.

A number of Peterbilts feature in the fleet although Kenworth is now the brand of choice with six new units to be delivered over the next 12 months to cater for business growth.

Cummins’ X15 Euro 5 engine rated at 550 or 600 hp is the preferred power specification, with 18 red engines currently in the fleet.

Uhlenberg family in front of truck

Whole-of-life support

“The switch to Cummins has been a very good experience for us. We have nothing but praise for the Cummins organization,” says Daryl.

“The whole-of-life picture is the key thing for us and we’ve got that nailed with the support we get from Cummins – parts availability, scheduled maintenance, life expectancy and in-frame rebuilds.

“So the red engines turn up, we run them to life, which is 900,000 to 1.2 million kilometers, and then Cummins does an in-frame overhaul in a timely manner. If there’s an issue, parts and support are close by.

“The support we get from Cummins Palmerston North is fantastic, second to none.”

Daryl recently looked under a Kenworth that was in the workshop for a service and was surprised to see no oil leaking from the one-million-kilometer X15. “I remember when I was a fitter we had to wear a raincoat when working under a truck,” he jokes.

Fuel agnostic

Acknowledging that the push to decarbonize is now “very real”, Daryl likes the idea of Cummins’ fuel agnostic concept where one base internal combustion engine, optimized to run on diesel, can also be customized to run on ultra-low and zero-carbon fuels like renewable natural gas and hydrogen.

“My father was a pioneer of linehaul trucking in New Zealand and he always embraced new technology. He was never scared of it,” he says.

“I tend to be a little more cautious but I can see where a 500 hp natural gas or hydrogen engine would work for us in short haul applications,” he admits. “We’re certainly willing to look closely at these alternative fuel technologies when suitable infrastructure is in place.”

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