From: jgd@dixie.com (John De Armond)
Newsgroups: misc.consumers.house
Subject: Re: propane generator
Date: 10 Oct 92 03:59:01 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.

randyw@iplmail.orl.mmc.com (Randy Walker) writes:

>  I am planning to determine the size generator I need by adding the wattage
>  used by such items as my well pump, refridgerator, microwave oven, a few
>  ceiling fans, solar water heater pump, etc.

It's a bit more complicated than that because anything with a motor 
requires much more power during starting.  My experience with a wide
variety of consumer-grade generators is don't figure on much more than 
about half the capacity  of the generator in load if the load is 
significantly motor in nature.  Your well pump in particular will require
a lot of power to start.

>  I want to buy a propane generator or convert a generator to run on propane.
>  The reasons are:

>  1. I want have a supply of fuel on hand, and gasoline has a limited shelf
>     life, where propane's shelf life should be unlimited.
>  2. I can store several "gas grill size" propane bottles in a small area.
>  3. I think that a bottle of propane will run a generator for quite a while.

It is a pretty straightforward calculation to compute how much energy
is in a 20 lb tank of propane.  It contains just a bit more than 4 gallons.
Propane provides about 80% of the energy per unit volume of gasoline.  My
latest experience in long term use of a generator was after my house burned
last year.  My 3800 watt Yamaha generator running about 3/4 loaded
consumed about 6 gallons of gasoline a day.  This was to run 2 'friges,
a freezer and a bunch of temporary lighting.  You should be getting
the idea that grill tanks are pretty useless in this application.

If you want to run on propane, I'd consider burying a 500 gal or even
a 1000 gal propane tank and plumb the generator in semi-permanently.
The tanks are not very expensive.  Burying will protect it from
disasters.  Figuring 8 gallons of propane a day (worst case, perhaps),
500 gallons would give you 63 days.  The great  unknown, of course, is
how fast propane filling service comes back after something like the 
hurricane.  I have no guesses on that.

I recently did a computation using local energy rates and in the summer
when I pay almost 12 cents a kwh, it would be cheaper for me to run
a natural gas fired generator.  I have not looked at propane since NG is
available to my house but it very well might look as good if you buy
in sufficient quantity.  The 1000 gal tank has a lot going for it there.
I used to operate a propane filling station at my store and when I 
swapped out the 500 gallon tank for a 1000 gal one, I could get significant
discounts.

Northern Hydraulics sells a line of dual fuel (propane/ng) generators,
though I'm not terribly enamored with them.  They use a Briggs and
Stratton engine.  My experience has been these obsolete engines consume
as much as twice the fuel as one of the modern OHV hondas or yamahas or
Wisonsins.  After the fire we temporarily had a B&S-powered 4 kw 
generator.  It was almost exactly a gallon an hour to run the same load
as the Yamaha ran on about 6 gallons a day.

You might also want to look at diesel generators.  They are more efficient,
quieter because of the lower speed and will probably last your lifetime.
Diesel/fuel oil is still slightly cheaper per BTU than propane and is
easier to store and handle.

John

-- 
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