Fuel Storage

Your generator will need fuel. Fuel that you will need to store from the time it is delivered to the time it is used. Your selection of a storage tank will depend on

• What type of fuel you are storing--whatever your generator uses

• How fast you use fuel, which in turn depends on how much electricity you expect to use

• How long you want to be able to last between "fill ups"

Fuel Types

Our generator will use one of three different fuels: propane, gasoline, or diesel.

Propane

Propane is stored in a special high pressure tank that is generally leased from your fuel supplier. The tank will be installed at your site by the fueler when you begin service and they will refill it on whatever schedule you need. The initial installation charge will include running a pipe from the tank.

One advantage of Propane is that it can be used not just for generating electricity but for water heating, house heating, and cooking as well. This means only a single fuel must be purchased and stored. This makes Propane the quickest and easiest setup for an off-grid retreat.

The most significant disadvantages of Propane are its the low energy content per volume and the use of modified gasoline engines in the generator set. Propane generators are nearly all built on converted gasoline engines. The conversion to Propane leaves intact all the complexity and short life of these engines. Propane does allow a gasoline engine to run cleaner and somewhat more quietly, but the engine design is unchanged, so reliability issues remain.

An off-grid retreat that is not used as a full time residence is a perfect candidate for Propane power. Such a homestead could be setup to use Propane for every appliance in the house, including refrigeration. The relatively limited life expectancy of the (converted gasoline) generator would be offset by infrequent use.

Gasoline

Generator sets that take gasoline as a fuel are very common and available from large home improvement and department stores. These units owe much of their heritage to the construction industry where they have traditionally provided on-site power at job sites. Gasoline engines are very light weight for their power output so that even a substantial generator can be made portable.

The problem with gasoline generators is three fold: reliability, cost, and safety.
Gasoline engines are the most complex internal combustion engines in common use requiring an ignition and fuel system that are composed of dozens of small parts. Since any part will eventually fail, the high failure rate of gasoline engines can be easily understood by looking no further than the total number of parts.

Compare a gasoline engine to a diesel. The diesel has a fuel pump that produces high pressure to an injector in each cylinder. The gasoline engine has a carburetor with at least three or four adjustments and a dozen moving parts and an ignition system comprising numerous mechanical and electrical parts that drive spark plugs in each cylinder. It is a wonder that they run at all!

Gasoline is the most expensive of the fuel choices available.

It blows up! Gasoline is incredibly dangerous. If we didn't use it in our cars, I'm sure the BATF would regulate it like other explosives.

The application of gasoline generators is simple. Just don't. Unless you need portable power at a job site [I own one for precisely that purpose] you should use Propane or Diesel instead.

Diesel

This is the safest of the fuels and the most economical. Diesel is just another name for the fuel oil that still heats many American homes. It is available for delivery nearly anywhere in the country and is cheaper than either Propane or gasoline.

It is also nearly impossible to light it by accident. A burning match can be put out by dipping it in diesel fuel--not so with gasoline!

Diesel engines are the simplest and most reliable internal combustion engines in common use. They have the fewest moving parts, fewest total parts, and fewest adjustments.

How Much to Store

That depends on two things:

• How much power you intend to use, and

• How much power each gallon of fuel will produce.

Power usage is a personal thing. Different folks in the same property will use different amounts of power. Your best estimation method is to look at your "in-town" power bill and extrapolate from their. A typical non-frugal suburban home can use as much as a 900 Kilowatt-hours per month. In a frugal "cabin" setting, even one that is occupied full time, a usage of 200 Kilowatt-hours per month or less is very possible.

The different generator and fuel combinations provide varying amounts of energy per gallon. Diesel is typically the most efficient at about 10 Kilowatt-hours per gallon. Gasoline will be about half the energy output of diesel (5 KWH/gallon) and Propane can be expected to provide ?? KWH/gallon.

Here's a simple example. Let's suppose that our expected energy consumption is 450 KWH/month (about 15 KWH/day). Let's also decide that a one to two month supply of fuel is what we would like to have on hand at any given time. A diesel generator will need 45 gallons of fuel oil per month for this usage level. A two month supply is 90 gallons.

Does that mean that a 90 gallon tank will do? Not quite. Since the tank must be used and refilled on some sort of schedule, our average fuel supply will be less than our total tank volume. If we have a tank that is sized for three months usage, then we can refill it at the 1/3 full mark and have anywhere from 1 to 3 months of fuel on hand at any given time.

Who is going to fill that tank? A commercial fueler is probably not going to be happy with delivering only 45 gallons to a remote property. You might need to either deliver (relatively small amounts) of fuel yourself, or use a larger tank that is refilled very infrequently.

Suppose we use a 500 gallon tank? At our (example) usage rate, this will last almost a year! There will be no trouble at all getting a commercial fueler to deliver 200 or so gallons when the tank reaches the half way mark about twice each year and you can rest assured that even the most sever weather will not outlast your fuel supply.

Used fuel tanks in large sizes are quite often available for a song. I have one that stores 750 gallons that I bought for $200. Some tanks I have seen offered for free just to get rid of them.