Diesel and Propane Generators

In most off-grid renewable energy systems, a fossil-fuel generator is a necessary part of the system. This is because solar, wind, and hydro are all dependent on environmental factors that fluctuate according to natural cycles and perhaps some random chance added to keep things interesting. For most people, the time will come when natural sources just don't gather enough energy for their needs, or some equipment failure necessitates a good backup plan. That's where the generator comes to save the day.

For grid-connected people, a generator is a good investment when nature drops a hurricane on your head, or some other event puts out the lights in your community. A good generator keeps the food in your freezer and refrigerator from spoiling and provides an alternative power source for the essential systems in your home.

Choosing the right generator for your needs is the key to success, but all too often people are swayed by shiny paint, low prices and wishful thinking. Yup, we've been there, along with lots of other unfortunate folks that we've spoken to. Sadly, one of the most common brands in America is also one of the worst choices, as evidenced by many tales of woe delivered by people searching for a replacement for the generator that failed to deliver as promised. Most generators commonly seen in hardware stores are not suitable for anything beyond occasional use. They are noisy, burn lots of fuel, and most are not wired properly to supply their full output in a useful way. Many who purchase this class of generator are disappointed.

If you don't see what you're looking for in our generator section, give us a call! Our suppliers offer a wide range of quality generators to fit most any need. We'll be happy to find jsut the right unit for you.

A Note About Generator Fuels

Most generators use either gasoline, propane, natural gas, or diesel fuel to provide power. A few "triple-fuel" models can use propane, natural gas, or gasoline interchangeably. There are certain advantages and disadvantages to each fuel type, and in the interest of making an informed purchase, I'll outline some of the differences:

DIESEL contains the most "heat energy" per-gallon of the commonly available fuels. That means the engine can produce more power for every gallon of fuel burned, and in most cases this provides the best economy. In many areas, tax-free "off-road" diesel is available for heavy-equipment and generator use. Diesel engines are usually built with heavier construction and tend to have a longer lifespan. Diesel engines do not have ignition systems that fail or require maintenance. These are some of the reasons that most heavy equipment and big trucks use diesel engines. Diesel engines produce higher torque at lower speeds, making it possible for the generator to run at only 1800 RPM. Slower speed contributes to longer engine life and usually means a quieter generator. Diesel fuel does not flow well in cold temperatures, requiring additives. Water contamination can be a problem, causing fuel lines to freeze and cause damage to fuel injectors. Fuel must be kept very clean and dry. Fuel additives and special filters usually overcome all of these obstacles. Diesel engines don't start easily in cold weather, so they have electric glow plugs as a starting aid. This usually solves cold weather starting issues.

GASOLINE has less heat energy than diesel, therefore offering lower fuel economy. Gasoline is readily available, and gasoline engines are less finicky about moisture in the fuel, but water can still cause poor performance, freezing fuel lines and plenty of trouble. Gasoline gets "stale" and can plug a carburetor if the engine is not exercised regularly. Gasoline engines have spark plugs and an ignition system that can fail. This is less of an issue with modern engines due to advances in electronic ignition systems. Gasoline engines generally generate less torque than diesel engines, therefore most gasoline generator sets run at 3600 RPM, instead of 1800 RPM for diesel engines. This creates more noise and faster wear. Gasoline engines are usually lighter in weight and generally start well in colder weather.

Propane (LPG) and Natural Gas have less heat energy per gallon than the other fuels. A triple-fuel generator engine will produce less horsepower when operated on these fuels, and therefore will usually consume more gallons-per-hour than either gasoline or diesel. Propane and natural gas are delivered and stored in sealed containers, so contamination isn't an issue. Cold weather starting is not usually a problem. Engines tend to have a longer life with these fuels (compared to gasoline), since they introduce few contaminents. Propane supply can sometimes be a problem in remote areas if a delivery is needed in winter and the fuel truck can't get in. Natural gas has the advantage of an endless supply, but the disadvantage of limited distribution. Most of these generators run at 3600 RPM, but some have sufficient horsepower and torque to run at slower speeds.

Generator Output Wiring

When shopping for a generator, it's important to get one that is wired correctly to fit your application. That's right, they're not all the same and buying the wrong one will ruin your day. Here's some general information that will help you make the right choice. If you're not sure, contact us for help.

Small, suitcase-size generators are built for portability and usually range from 800 to 2,000 watts. Most of these units are wired for 120 volt output only and this is appropriate for their use, which is generally just small appliances and lighting. These generators are appropriate for very small battery/inverter systems only, where there are no 240-volt loads.

"Hardware store" generators are the sort that you'll likely see in your local home improvement center, generally ranging from 3,000 to 10,000 watts. They're designed to be portable, but not to be carried by one person. Usually, these units have a split-phase alternator that delivers both 120-volts and 240-volts. There will usually be several 120-volt outlets available and at least one 240-volt outlet. Some of the 120-volt outlets are connected to 1/2 of the alternator wiring and the other 120-volt outlets are connected to the other 1/2 of the winding. This means that the generator can only supply 1/2 of its output wattage to a single 120-volt load. If your inverter system runs on 120-volts, you can only use 1/2 of the generator power! So a 6,000 watt generator will only supply 3,000 watts to that 120-volt outlet, which probably won't be enough to power your system. Sometimes the generator is configured so that the full output wattage is available at the 240-volt outlet, but often it is not. Even if the 240-volt outlet is wired for full power, you can't use it unless you have a 120/240-volt split-phase inverter system. Note that there are rare exceptions (mostly a few Honda models) that have the ability to supply full generator output to a single 120-volt outlet with the use of a selector switch.

High-grade generators usually have a 120/240 volt split-phase alternator that can be easily altered (by changing a few connections) to supply full power at 120-volts, OR wired for standard 120/240 split-phase operation. Although there are many model choices, we usually supply generators that have this feature and are designed to be direct-wired to your system. This eliminates expensive plugs, bad connections, and inadequate wire sizes.