Six Common Types of Generators … and One That May Surprise You

  1. Gasoline

    Of all the options on the list, gasoline generators are among the most common, primarily because gasoline is readily available and these generators are on the low-end of the cost scale. However, gasoline is usually unavailable during power outages, because it requires electricity to pump. Gasoline generators are available in small sizes, ideal for portable models, but the fuel is highly flammable.

    Gasoline lasts less than one year when stored, and gas prices are comparatively higher than diesel, propane, and natural gas. Gasoline generators produce relatively high emissions, do not typically last as long as some other models, and do not tend to start well in colder temperatures.

  2. Diesel Fuel

    Diesel is the least flammable of all the fuel sources, and is almost as readily available as gasoline. These engines have long lifespans, and perform more efficiently while lasting longer under heavy, rigorous use, so long as they are properly maintained. Diesel generators are affordable to operate, though these units typically cost more than gas generators. Some states, counties, and municipalities allow farm operations to purchase diesel at a reduced tax rate, or without tax levies at all. Additionally, diesel generators start relatively easily in cold environments.

    However, diesel fuel is only good up to 24 months in storage, and storing large quantities can be expensive. Like gas, it’s often impossible to pump diesel during power outages. Because diesel engine emissions are quite high, some areas limit the number of hours these engines can be operated per day due to environmental concerns.

    Moisture in the fuel ruins it (unless it is emulsified diesel, discussed below), so it is not well suited to wet environments, such as those near lakes and rivers or outdoors in the elements. Diesel generators require regular maintenance by a qualified mechanic, and are heavier engines, therefore less portable.

  3. Bio Diesel

    Bio diesel fuel is made from a mixture of diesel and another biological source, such as vegetable oil or animal fat. The pros and cons of bio diesel are similar to those of ordinary diesel fuel, only with more environmental benefits. Bio diesel uses less of the non-renewable energy source of fossil fuels, and burns with lower emissions and less waste. This makes it an environmentally friendly option compared to regular diesel. All diesel fuels are less flammable than the other liquids and gasses on this list, but these engines are also noisy.

    Like diesel, bio diesel lasts two years or less in storage, and is sometimes unavailable during a power outage because it cannot be pumped. It is also harder to find in some regions. Because the mixture of diesel to oil must be kept at a ratio of 80:20, it is considered more difficult to work with.

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  4. Emulsified Diesel

    Emulsified diesel is a mixture of diesel fuel and water blended with a mixing agent. It shares the pros and cons of diesel and biodiesel fuels. As with bio diesel, emulsified diesel produces fewer emissions than ordinary diesel and consumes less fossil fuels. It too has a shelf life of two years or less, and maintaining the proper ratio of water to diesel is challenging, especially in hectic work environments.

  5. Propane Gas (Vapor and Liquid)

    Propane boasts a longer shelf life than gasoline or diesel fuels, and burns far cleaner. It is easily stored in any quantity, and is readily available even during power outages. Propane produces relatively low emissions, and is not subject to “wet stacking” common in diesel generators. Propane generators are generally affordable, and last a long time. Propane also starts easily in cold temperatures, and offers quiet operation.

    On the con side, propane is kept under pressure, and is highly flammable, even explosive. The fuel systems are more complex, therefore subject to failures that are more frequent. Installation costs are higher, because a qualified technician must install the gas lines. Propane generators are more expensive to buy and operate, burning about three times the amount of fuel as comparable diesel engines. Additionally, propane units typically do not have long life expectancies compared to some other generator types.

  6. Natural Gas

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    Natural gas is readily available in almost every location, and the new shale reserves opened up by fracking techniques mean a virtually limitless supply. Because natural gas lines are run to the site of operation, these generators never run out of fuel or need to be refilled. This also means that the generators are not portable.

    Natural gas generators burn cleanly with very little waste, and the gas is readily available even in the absence of a power supply. These units are also affordable in comparison to other choices. Natural gas also starts well in cold conditions, and runs relatively quietly.

    The disadvantages of natural gas generators include higher installation costs, due to running the gas lines. These generators do not typically last as long as diesel generators, and if the gas lines are broken this could lead to a dangerous leak. Like propane, there is no issue with “wet stacking” when operating a natural gas generator.

  7. Surprise! Hydrogen

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    Since the 1800s, people have worked on developing a generator that could produce power from hydrogen. Hydrogen is tremendously abundant (particularly from water sources), is non-toxic, clean, cheap, and produces more energy per pound than any other fuel source.

    In the 1940s, experiments began to create a hydrogen powered vehicle, and attempts continue today. Though not as readily available as some other types of generators, hydrogen generators are portable and useful for many environments, including laboratories. When equipped with proper safety features, hydrogen generators are also safe and portable.

    The primary consideration when choosing a generator is the type of environment where the equipment is pressed into service. Balance budgetary requirements with safety factors, the need for portability, the temperature of operating conditions, and how easy it is to refuel when supplies are low.