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What size generator to run AC??

supercub
Explorer
Explorer
Looking at buying a +/-28 foot travel trailer, with one AC unit. What size generator should I have to run the AC and lights, TV, etc?
Thanks
45 REPLIES 45

Microlite_Mike
Explorer
Explorer
Gdetrailer wrote:
Additionally, you get nailed on the price of propane in small portable cylinders since in small cylinders they sell it by the pounds.


I haven't purchased Propane in my travels (West of Rockies mostly) where my "portable" tanks were filled by weight. The person filling just connected hose to tank, pumped in propane, then gave me a ticket with meter reading written on it for cashier. Truck Stops, Propane Distributors, Campgrounds, Gas Stations, and even places like Tractor Supply and Convenience Stores, all BY THE GALLON.

In my State any scale used for "Commerce" has to be tested and certified by our State Dept of Agriculture weights and measures division. The meters are easier for them to test, certify, and seal, than a scale which could be "altered" once the inspector's vehicle is out of sight.

I also haven't had to remove my tanks from the tongue of my Trailer for decades. I stop my Trailer where it can be reached by the hose and they're filled in place.

As for my 3500W Inverter Dual Fuel, I run propane when I need the A/C overnight. I get 6-7 hours on a tank of gasoline with A/C running and I can get twice that from a 20# tank of propane (which I carry two of in my truck).

For me it's a matter of not having to interrupt my sleep to tend to the generator's fuel when it's hot and muggy all night.
"Knowledge is realizing that the street is one-way, wisdom is looking both directions anyway."


~ Albert Einstein

valhalla360
Nomad III
Nomad III
Bobbo wrote:
valhalla360 wrote:
With the 5 gal jug, I then need to hold it up while pouring, using the asinine eco-spouts that require 6 hands to operate and still drizzle fuel over the top of the generator for 2-3 minutes




I actually have a syphon hose but regardless, you still have to hold the jug while the fuel is transferring...so it's a bit lighter but you still have to lift it for much longer.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

Bobbo
Explorer II
Explorer II
valhalla360 wrote:
With the 5 gal jug, I then need to hold it up while pouring, using the asinine eco-spouts that require 6 hands to operate and still drizzle fuel over the top of the generator for 2-3 minutes


Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab w/Max Tow Package 3.5l EcoBoost V6
2017 Airstream Flying Cloud 23FB

valhalla360
Nomad III
Nomad III
Gdetrailer wrote:
Regardless, propane is overall less desirable "alternative" to gasoline when it comes to loss of wattage (the terminology you are looking for is "DE RATED").

Propane contains LESS energy per GALLON than gallon of gasoline.

.............


to build a trailer to haul a 250 gallon propane tank with you you are stuck with retail by the pound pricing.

Propane gens also have additional demand regulator, which can foul up, propane doesn't vaporize fast in cold temps which can cause fuel starvation and can even stop vaporizing in cold temps..

Propane isn't always propane, some areas you may get butane at a higher mix in your propane and butane is less BTUs and burns at a slower rate which affects just how well your engine performs and final wattage output.

Something else to consider, "dual fuel" setups are a "COMPROMISE" and overall most small engines are built and tuned for gasoline, the timing and compression are typically optimized for gasoline and not propane..

It sounds good on paper, but in real world use, a compromise is a compromise..

If you don't mind moving 20 lb to 30 lb cylinders (which weigh 38 lbs and 58 lbs each respectively) all the time while camping then have at it, but myself that sounds like a real hassle..

Some of you guys are really way over dedicated to making camping a lot more about doing chores than relaxing.


If you are trying to operate on a single 2000-2200w generator, the derating is an issue as you are marginal running the air/con at the full gasoline rating. When talking about a 4500w generator or a pair of 2000w generator's ganged together, the derating is irrelevant as it's still more than enough power.

Yes, propane is less energy dense but propane is also cheaper per gallon. Largely it's a wash (or close enough that I don't care):
- 4.6gal propane (#20lb tank) is equivalent to 3.4gal of gasoline in terms of total stored energy. I paid $20 to fill a 20# tank last week. At current prices, that would be $17 in gasoline. I don't run the generator 24/7 for weeks on end, so it's close enough as to not matter.
- If you are comparing to a 250 gal propane tank, you would need 185 gal gasoline tank...neither is a great option when mobile though if you are talking about a seasonal site, lots of propane places will drop a big tank for free if they can bring the truck by and fill it up for you (In fact, we have friends who did just that).

Extreme cold is an issue at peak loads but I don't usually run the air/con in those conditions.

Any place with lots of butane in the mix is not going to have extreme cold. Of course, in N. America, it's largely urban legend with most places having less than 5% even in warm areas.

Yes, propane cylinders weigh a little more but it's lift out of the truck and set next to the generator...done. With the 5 gal jug, I then need to hold it up while pouring, using the asinine eco-spouts that require 6 hands to operate and still drizzle fuel over the top of the generator for 2-3 minutes...so as you say...on paper it sounds good being lighter.

But really the driving issue is reliability. Propane is far less likely to gunk up. Even if after 10yrs, the regulator fails, that's a 5min replacement to swap out with a new one. I fought with the old Yamaha gas generator for a couple years surging. Even had a couple small engine guys try with limited success. $300 for a new carb that will gunk up again or sell it for $300 and get a bigger dual fuel unit for $800.

Yes, there are use cases where gasoline makes sense but for your average RVer who uses it a few days per year, propane is really the way to go.

PS: With dual fuel, I can always revert to gasoline if I do run across a use case where gasoline is preferable.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

Huntindog
Explorer
Explorer
As noted, all of the propane downsides are true.
There is one and only one advantage to propane. No carb to gum up.

Now this is an important advantage to those that do not use their generators much... And that covers a lot of people.
As I have said here before, "Propane is well suited for light users. Gas is s better choice for heavy users.
I was a heavy user for many years. My two EU 2000s never had any carb issues. Boondocking as I do in remote locations, propane was an unworkable fuel for us.
Now with 1860 watts of solar, my usage is less most of the time. But I am keeping the Hondas around for those cold weather winter hunts that require a LOT of generator use.
Huntindog
100% boondocking
2021 Grand Design Momentum 398M
2 bathrooms, no waiting
104 gal grey, 104 black,158 fresh
FullBodyPaint, 3,8Kaxles, DiscBrakes
17.5LRH commercial tires
1860watts solar,800 AH Battleborn batterys
2020 Silverado HighCountry CC DA 4X4 DRW

bgum
Explorer
Explorer
There you folks go using facts again to support your position.

Gdetrailer
Explorer III
Explorer III
valhalla360 wrote:
Gdetrailer wrote:

You forgot to mention a few "downsides" of propane for a generator..

First and foremost, propane has less energy density than gasoline, this means your engine will deliver less HP which translates to less generator wattage available per gallon of fuel.

It appears you are mixing two things together.
- On propane, the engine will produce less wattage (or HP which is the same thing) but it's nor per gallon. Of course with a 4500w generator or paired 2500w generators, that's a non-issue on a 30amp RV to run the air/con.
- The stored energy per gallon is about run time not maximum wattage.


You will burn through a lot more propane in the process, not a big issue if you are not mobile or moving about and can tap into a large propane tank..

But you will burn thru less gasoline and in a pinch with dual fuel, you can switch back to gasoline.

A 20lb propane tank or a 5 gal gas jug eats up close enough to the same space in the truck bed.


20 lb portable cylinders hold a max of 4.6 Gallons of liquid propane, if you use propane "exchanges" you do not get 20 lbs worth of propane, you get max of 15 lbs, roughly 3.6 gallons of propane..

Yes, the swap places typically give you 15lb but the fill places you get the full amount.

.........

There are also far, far fewer propane dealers than gas stations and most propane dealers shut their doors after 5 PM and may not be open on weekends. Pretty easy to find gas stations open up to 11 PM or even open 24hrs and open on Sat and Sun..

I prefer filling but in a pinch, it's easy to find swap places. Also, I'm filling a tank when it's empty, so I'll just switch to a full tank if it's 11pm.

So, basically one would need to have multiple 20 lb - 40 lb cylinders just for the gen, switching them out to run a gen for a week. Not to mention handling/hauling them around to camp and to a propane dealer while camping. A full twenty pound cylinder weighs approx 38-39 lbs, 5 gallon gas can will weigh around 31 lbs and get longer run time.


Running the generator 24/7 for a week...we'd probably move to a campground in those conditions, so we could plug in. We have 2 tanks on the trailer and 2 in the truck bed. Since 1 tank will easily last us a month or more, in a pinch, we could steal one of the ones off the trailer giving us 3 available for generator use.

If small engines didn't have the carbs get gunked up, I would agree that gasoline is the way to go but the simplicity and reliability of propane shifted us in favor of a dual fuel unit.


Regardless, propane is overall less desirable "alternative" to gasoline when it comes to loss of wattage (the terminology you are looking for is "DE RATED").

Propane contains LESS energy per GALLON than gallon of gasoline.

For instance..

Per HERE

Propane- 1 gallon = 91,452 Btu
Gasoline- 1 gallon = 120,286 Btu

So what you say?

Well less BTU content means less work done and in the case of a generator it takes MORE propane in gallons than gasoline to do the SAME work as gasoline.

Additionally, you get nailed on the price of propane in small portable cylinders since in small cylinders they sell it by the pounds.. Bulk sellers once you get into large tanks sell it by the gallon but unless you want to build a trailer to haul a 250 gallon propane tank with you you are stuck with retail by the pound pricing.

Propane gens also have additional demand regulator, which can foul up, propane doesn't vaporize fast in cold temps which can cause fuel starvation and can even stop vaporizing in cold temps..

Propane isn't always propane, some areas you may get butane at a higher mix in your propane and butane is less BTUs and burns at a slower rate which affects just how well your engine performs and final wattage output.

Something else to consider, "dual fuel" setups are a "COMPROMISE" and overall most small engines are built and tuned for gasoline, the timing and compression are typically optimized for gasoline and not propane..

It sounds good on paper, but in real world use, a compromise is a compromise..

If you don't mind moving 20 lb to 30 lb cylinders (which weigh 38 lbs and 58 lbs each respectively) all the time while camping then have at it, but myself that sounds like a real hassle..

Some of you guys are really way over dedicated to making camping a lot more about doing chores than relaxing.

valhalla360
Nomad III
Nomad III
Gdetrailer wrote:

You forgot to mention a few "downsides" of propane for a generator..

First and foremost, propane has less energy density than gasoline, this means your engine will deliver less HP which translates to less generator wattage available per gallon of fuel.

It appears you are mixing two things together.
- On propane, the engine will produce less wattage (or HP which is the same thing) but it's nor per gallon. Of course with a 4500w generator or paired 2500w generators, that's a non-issue on a 30amp RV to run the air/con.
- The stored energy per gallon is about run time not maximum wattage.


You will burn through a lot more propane in the process, not a big issue if you are not mobile or moving about and can tap into a large propane tank..

But you will burn thru less gasoline and in a pinch with dual fuel, you can switch back to gasoline.

A 20lb propane tank or a 5 gal gas jug eats up close enough to the same space in the truck bed.


20 lb portable cylinders hold a max of 4.6 Gallons of liquid propane, if you use propane "exchanges" you do not get 20 lbs worth of propane, you get max of 15 lbs, roughly 3.6 gallons of propane..

Yes, the swap places typically give you 15lb but the fill places you get the full amount.

.........

There are also far, far fewer propane dealers than gas stations and most propane dealers shut their doors after 5 PM and may not be open on weekends. Pretty easy to find gas stations open up to 11 PM or even open 24hrs and open on Sat and Sun..

I prefer filling but in a pinch, it's easy to find swap places. Also, I'm filling a tank when it's empty, so I'll just switch to a full tank if it's 11pm.

So, basically one would need to have multiple 20 lb - 40 lb cylinders just for the gen, switching them out to run a gen for a week. Not to mention handling/hauling them around to camp and to a propane dealer while camping. A full twenty pound cylinder weighs approx 38-39 lbs, 5 gallon gas can will weigh around 31 lbs and get longer run time.


Running the generator 24/7 for a week...we'd probably move to a campground in those conditions, so we could plug in. We have 2 tanks on the trailer and 2 in the truck bed. Since 1 tank will easily last us a month or more, in a pinch, we could steal one of the ones off the trailer giving us 3 available for generator use.

If small engines didn't have the carbs get gunked up, I would agree that gasoline is the way to go but the simplicity and reliability of propane shifted us in favor of a dual fuel unit.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV

Gdetrailer
Explorer III
Explorer III
Baja Man wrote:
supercub wrote:
Thanks for the replies, sounds like perhaps the best way is to get a couple of portable 2000 watt gens.


Just what I did.....

Two Champion Dual Fuel 2500W inverters

I didn't want to carry gasoline, clogged carbs from gas sitting, etc.
Propane is clean and readily available.

Each inverter is 39#
dBA is 59 at 23' (Honda is 48-57 at 23')

I believe my set up is great. Light, easy to handle, plenty of power, can use just one if no AC is being used, two fuels, and portable enough for other uses.


You forgot to mention a few "downsides" of propane for a generator..

First and foremost, propane has less energy density than gasoline, this means your engine will deliver less HP which translates to less generator wattage available per gallon of fuel.

You will burn through a lot more propane in the process, not a big issue if you are not mobile or moving about and can tap into a large propane tank..

20 lb portable cylinders hold a max of 4.6 Gallons of liquid propane, if you use propane "exchanges" you do not get 20 lbs worth of propane, you get max of 15 lbs, roughly 3.6 gallons of propane..

Typically with say a 3Kw gen, you most likely will burn through a full twenty pound cylinder (not an 15 lb exchange cylinder) every 24hrs assuming you run the gen 24/7!

HERE is a website that helps calculate your propane use by a generator..

There are also far, far fewer propane dealers than gas stations and most propane dealers shut their doors after 5 PM and may not be open on weekends. Pretty easy to find gas stations open up to 11 PM or even open 24hrs and open on Sat and Sun..

So, basically one would need to have multiple 20 lb - 40 lb cylinders just for the gen, switching them out to run a gen for a week. Not to mention handling/hauling them around to camp and to a propane dealer while camping. A full twenty pound cylinder weighs approx 38-39 lbs, 5 gallon gas can will weigh around 31 lbs and get longer run time.

pianotuna
Nomad II
Nomad II
I prefer a single remote electric start generator.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Baja_Man
Explorer
Explorer
supercub wrote:
Thanks for the replies, sounds like perhaps the best way is to get a couple of portable 2000 watt gens.


Just what I did.....

Two Champion Dual Fuel 2500W inverters

I didn't want to carry gasoline, clogged carbs from gas sitting, etc.
Propane is clean and readily available.

Each inverter is 39#
dBA is 59 at 23' (Honda is 48-57 at 23')

I believe my set up is great. Light, easy to handle, plenty of power, can use just one if no AC is being used, two fuels, and portable enough for other uses.
2023 GMC, 3500HD, Crew Cab, 6.6L Gas/6 Speed Auto, 4X4, Standard Bed; SRW
2011 Outback 250RS - Anniversary Edition
Equal-i-zer 10K

TomG2
Explorer
Explorer
supercub wrote:
Looking at buying a +/-28 foot travel trailer, with one AC unit. What size generator should I have to run the AC and lights, TV, etc?
Thanks


To supercub. Most RV parks and your trailer have 30 amp ratings. 30 X 120 = 3,600 watts. That is what I shoot for if I want the same capability as the shore power in most parks.

72cougarxr7
Explorer
Explorer
I went with a Champion 3400 inverter and couldnt be happier!
Quiet, wheels around nicely, electric start so my wife can start it. Runs my ac easily, it sounds like its running at half throttle or less with ac on.
Maintenance is easy. I bought it in 2019 and have not had 1 issue with it.

supercub
Explorer
Explorer
Thanks for the replies, sounds like perhaps the best way is to get a couple of portable 2000 watt gens.