What size generator to run AC??

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.