RV Generator Size

[Tulecreeper]

I know quite a bit about generators - I have two, one one for power tools, and one that runs the house through an emergency transfer switch when there is a power outage. What I don't know about are inverter generators.

I'm thinking that even with a 50A service in my RV, a 4000W - 4500W (33 amps - 38 amps) generator should be acceptable. Even with two A/C's running, the odds of both compressors coming on at exactly the same time are slim. So, I'm looking for suggestions for that size genny that weighs as little as possible...say no more than 120-pounds. I don't have a 25-year-old back anymore. And again, thanks a bunch for the info!

 

[Martian]

To make use of both AC units you will have to supply both 50 amp legs with power. As far as generator size goes, add your two AC units and any other draw you will be using and use that as a starting point as start up of a compressor will draw a considerate amount extra for a short time. I am sure others have details on how to feed both legs.

 

[Mark_K5LXP]

The hazard you run into with inverter gensets is startup loads - some handle transient currents better than others. So while the running amps of the A/C unit might be within ratings, the startup draw becomes the question. Some gensets handle it better than others. One way is to over spec the generator but that adds cost, weight and fuel. Managing the peak load with a "soft start" kit can help. Careful with under-spec'ing your use overall, even with just one A/C unit all it takes is a couple "sneaky" loads like a compressor fridge and the converter charging house batteries and you're tripping the overload.

Mark B.
Albuquerque, NM

 

[Tulecreeper]

The hazard you run into with inverter gensets is startup loads - some handle transient currents better than others. So while the running amps of the A/C unit might be within ratings, the startup draw becomes the question. Some gensets handle it better than others. One way is to over spec the generator but that adds cost, weight and fuel. Managing the peak load with a "soft start" kit can help. Careful with under-spec'ing your use overall, even with just one A/C unit all it takes is a couple "sneaky" loads like a compressor fridge and the converter charging house batteries and you're tripping the overload.

Mark B.
Albuquerque, NM

Thanks for the reply.

Yes, I'm installing a soft-start kit on each A/C. That should help quite a bit. A 15k A/C pulls about 13 amps when running, and peaks at about twice that (26 amps) for a couple seconds when the compressor kicks on. Cost for the generator is not much of a consideration, so I'll pretty much pay for whatever I need. One of the things I "need" is a genny that weighs in at no more than 120-pounds. If I could get a 6500W generator in that weight class I'd pay for it. Unfortunately, the only ones I've found in that range are no more than about 4kW.

 

[UTTransplant]

It takes an awfully big generator to run equivalent to 50 amp shore power. My MH uses an 8000w generator to do it, and the rigs with 3 ACs get a 10,000w generator. You won’t be picking up anything like that. Can you survive on just one AC while running your water heater on propane? If so, two 2000-2200w inverter generators will fit the bill. Each weighs less than 50 pounds. Note the 4000w version runs ~120 pounds.

 

[Tulecreeper]

It takes an awfully big generator to run equivalent to 50 amp shore power. My MH uses an 8000w generator to do it, and the rigs with 3 ACs get a 10,000w generator. You won’t be picking up anything like that. Can you survive on just one AC while running your water heater on propane? If so, two 2000-2200w inverter generators will fit the bill. Each weighs less than 50 pounds. Note the 4000w version runs ~120 pounds.

I can absolutely adjust usuage to manage for amp-draw. My question was basically, how big of an inverter generator can I get and still keep it below 120-pounds? I really don't want to be dealing with running 2 generators hooked in parallel, but would be willing to look at some if they don't have a very large "footprint" and can fit in available storage..

 

[Tulecreeper]

For some reason I cannot edit my posts, so I have to just add another one.

I think another way to ask my question is: What is the smallest generator I can get with a 50A outlet on it? It will have 4 pins and say "120/240 AC" above the plug. If I have to buy a generator with a 30A outlet and use a 50A-30A dogbone adapter then I am defeating the purpose of having a 50A service.

 

[Steven L]

For some reason I cannot edit my posts, so I have to just add another one.

I think another way to ask my question is: What is the smallest generator I can get with a 50A outlet on it? It will have 4 pins and say "120/240 AC" above the plug. If I have to buy a generator with a 30A outlet and use a 50A-30A dogbone adapter then I am defeating the purpose of having a 50A service.

Here's the lightest one I'm aware of that includes a 50A outlet, but its rated to only 8000W running with a 10,000W surge capability. Just a touch under 210#, and other makes and models I've seen only grow in weight from there right out to 350#.

Gas Portable Generator 10000W Remote Start 120/240V

Whether you prepare your home for an approaching storm or power up for your next event, this generator provides power on demand with 8000 running Watts and 10000 starting Watts. The FIRMAN P08004 is an ideal choice of portable generators from our class of performance generators and can do almost...

firmanpowerequipment.com

 

[ButchW]

GeneratorBible.com - Leader In Portable Generators Stats & Comparison

Use our specialized tools to compare detailed stats of 517 portable generators across 25 brands and purchase the generator of your dreams.

generatorbible.com

This list a lot of generators by different criteria… Maybe it’ll help…
Butch

 

[Steven L]

GeneratorBible.com - Leader In Portable Generators Stats & Comparison

Use our specialized tools to compare detailed stats of 517 portable generators across 25 brands and purchase the generator of your dreams.

generatorbible.com

This list a lot of generators by different criteria… Maybe it’ll help…
Butch

Using the site above I found only 3 Inverters that would run in excess of 7500W which also have a 50A outlet available as well. This link should get you to that list all of them are within 5# one way or another of 240# however.

Inverter Generators - All Models & Specs

Browse our impressive selection of 226 inverter generators to find the best unit for your needs.

generatorbible.com

 

[Gary RV_Wizard]

My 50A/220v motorhome had a lot of electrical appliances but still operated everything nicely on about 45-50/120v amps total (5400-6000 peak watts), spread over two hot "legs" . If I was willing to accept a little more breaker risk, 35 amps (4200 watts) would do it, but the second a/c would trip occasionally. With two a/c, a water heater and the fridge cycling on their thermostats, there is going to be the occasional overlap in amp draw that breaks the bank.

I get the weight limitation, though. Find a 4000W genset that has a high enough peak rating that it can tolerate a 1500W surge for a couple minutes and you should find it manageable. Or do what many others have done, i.e. use two generators that can be paralleled. E.g. two Honda eu22001 or similar. That way you only have to deal with about 65 lbs at a time.

 

[Babe2201]

When we had our TT we used a 4650 watt champion generator and it ran A/C fine but we only had 1 not 2 so not sure if that would have worked or not. I am wondering if you could only use one of the A/C units at a time. I think that would be better than taking a chance on both kicking on at same time and shutting off generator.

 

[Mountain high]

Power loss due to high elevation is what I account for in our generators. We own three with one in our 2023 TT. Our home is at 6,000 feet and the local campgrounds are at or above 10,000 feet.

March 2006 dated article...

"Power Loss at High Altitudes

Any engine will produce a given amount of power based upon how much fuel and air it consumes. High power loads and RPMs consume more fuel. Because fuel and air are in a somewhat constant ratio, the engine will require more air at higher power outputs. Unfortunately, as we drive our motorhomes up into higher elevations, the air gets thinner and the engine loses it's ability to produce it's maximum rated power. This results in a corresponding drop in generator output wattage.

Different engines will react in varying amounts. For instance, the output wattage of the Onan Marquis Gold series of gasoline powered generators will lose 3.5% for every 1,000' in altitude gain over 3,000'. The Onan QuietPower Diesel 10,000 watt will derate 3.5% for every 1,000' over 500' and it further derates by 1% for every 10� F increase in temperature over 85� F. A good rule of thumb for most gensets is that you will lose 10% of the rated output every time you gain 3,000' in altitude. This means that a 7,500 watt generator running at 9,000' of altitude will only be capable of producing a bit over 5,000 watts at that altitude.

Diesel engines are pretty well able to handle the fuel injection requirements at higher altitudes but carbureted gasoline powered engines do not have that luxury. The Onan Marquis Gold series of generators uses carburetors. These gensets do have an altitude compensation adjustment on the carburetor. By dialing in a higher altitude you will lean out the mixture to prevent spark plug fouling and excessive smoke. It is very important that you also dial it back when descending to lower altitudes or else the engine will run lean and you will burn the engine's valves."

RV Tech Library - Power Loss at High Altitudes

 

[Steven L]

...Or do what many others have done, i.e. use two generators that can be paralleled. E.g. two Honda eu22001 or similar. That way you only have to deal with about 65 lbs at a time.

I have a EU2200i as well that I plan on running in series with the companion EU2200ITAN1 as my workhorses to start off with.

I definitely want to stay with quieter units than the 5000W dinosaur of a Devilbliss we use up at deer camp. You can literally hear that noise bomb well over a couple country miles away

 

[Tulecreeper]

GeneratorBible.com - Leader In Portable Generators Stats & Comparison

Use our specialized tools to compare detailed stats of 517 portable generators across 25 brands and purchase the generator of your dreams.

generatorbible.com

This list a lot of generators by different criteria… Maybe it’ll help…
Butch

Using the site above I found only 3 Inverters that would run in excess of 7500W which also have a 50A outlet available as well. This link should get you to that list all of them are within 5# one way or another of 240# however.

Inverter Generators - All Models & Specs

Browse our impressive selection of 226 inverter generators to find the best unit for your needs.

generatorbible.com

Both great sites...thanks!

 

[Tulecreeper]

My 50A/220v motorhome had a lot of electrical appliances but still operated everything nicely on about 45-50/120v amps total (5400-6000 peak watts), spread over two hot "legs" . If I was willing to accept a little more breaker risk, 35 amps (4200 watts) would do it, but the second a/c would trip occasionally. With two a/c, a water heater and the fridge cycling on their thermostats, there is going to be the occasional overlap in amp draw that breaks the bank.

I get the weight limitation, though. Find a 4000W genset that has a high enough peak rating that it can tolerate a 1500W surge for a couple minutes and you should find it manageable. Or do what many others have done, i.e. use two generators that can be paralleled. E.g. two Honda eu22001 or similar. That way you only have to deal with about 65 lbs at a time.

I found a couple in the 4000W-5000W range (working wattage) that will probably do the job just fine, and that weigh less than 120#'s. They're not all inverter-types, though.

 

[Tulecreeper]

When we had our TT we used a 4650 watt champion generator and it ran A/C fine but we only had 1 not 2 so not sure if that would have worked or not. I am wondering if you could only use one of the A/C units at a time. I think that would be better than taking a chance on both kicking on at same time and shutting off generator.

Since we plan on homesteading in southern AZ, there is a 100% certainty that we will need both A/C's at times between July and September. The odds that we will need both AND be running on generator power simultaneously is slim but I want the capability for short periods if necessary.

 

[ButchW]

Both great sites...thanks!

Y/W.. I found this pretty easy... I don't know how accurate or comprehensive it is, but there is a lot of usable info...
Butch