Types of Generators and Fuel Economy

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Generators or "gensets" come in various fuel choices that include gasoline, propane, natural gas and diesel. Cheaper gensets are built around gasoline engines running at 3600 rpm. Bigger industrial units tend to use natural gas, diesel or propane with a slower and more frugal 1800 rpm engine. Your model choice depends on factors such as unit capital cost, accessibility to fuel source, ease of use and economy. An environmental perspective would recommend an EPA (Environmental Protection Agency) rated four-stroke engine with slower speeds (about 1800 rpm or less). Urban applications usually go for natural gas.

The types of fuel are:

  • Gasoline: North America is very well versed in small gasoline engines that come cheap and are easily fueled, with a very short life span, especially in demanding situations. Most gasoline engines run at 3,600 rpm which causes rapid wear and tear with high noise output. Off-grid applications offer an estimated 5 years life before a big rebuild is necessary.
  • Natural Gas: Comes in either industrial-sized or converted gasoline form. The latter functions like the gasoline engine with the advantage of no fuel handling due to its direct connection to the gas supply line. The industrial-sized units are heavier, with a slower operation rate of 1800 rpm. Engine life is prolonged and noise is greatly reduced. Natural gas is not always readily available due to the limited pipelines for fuel transport.
  • Propane: Propane works similarly to natural gas and is an off-grid and rural preference. If propane is already being used to fuel some of your home's appliances, generator connection will be easy, while also eliminating another fuel source to your home.
  • Diesel: This type of engine is very durable and long-lasting. Units are heavy and have a slow-speed operation for the best fuel economy. Modern diesel engines offer very good start-up capabilities, even in cold weather conditions and are clean-burning. However, they cost more to purchase and operate with higher noise levels that require a sound-damping enclosure.
  • Biodiesel: This type of engine uses a clean-burning alternative fuel that can be produced from your home's renewable resources. No petroleum is needed, although the B20 blend in an 80:20 ratio – petroleum diesel to biodiesel - works without any major modifications to the engine. Biodiesel is biodegradable, simple to use and non-toxic while being free of aromatics and sulfur. The disadvantages of biodiesel are its lack of availability, high cost and difficult operation in cold weather.

A propane genset of 8 kW consumes 1.93 gallons or 7.3 liters per hour when running at 100% capacity. A similar natural gas-fueled genset consumes 144 cubic feet every hour (4,077 lph). A China Diesel Import model consumes barely 0.78 gallons every hour (3 lph).

A biodiesel or diesel model consumes 40% less fuel than a propane generator of similar capacity when in operation or charging batteries. Over the engine's lifespan, diesel models give great savings on operating costs whereas gasoline engines have relatively bad fuel economy.

Another downside to gasoline is the compulsory "road tax" to be paid at every fill. You can buy cheaper,