The Best Backup Power: Types of Generators

Portable Generators – 1kW to 10kW Output

As their name implies, portable generators are small and light enough to be moved from place to place. They can be stored and brought into use when needed and don’t need to be permanently wired into your home or business’s electrical system. Portable generators are self-contained, affordable and easy to use but, by their nature, are limited in total capacity and endurance. You may find that you will have to be selective about what equipment and systems you run when relying on a portable generator – all but the very largest models won’t have the capacity to run things like air conditioning, refrigerators and electric cookers simultaneously. Portable generators also carry their own fuel supply, which also limits their endurance.

1. Gasoline Portable Generators

The most affordable and portable generators use gasoline engines, which are cheaper to manufacture and lighter than diesel engines of the same power. They’re also significantly quieter and are better suited to long periods of running at light or variable loads.

Gasoline portable generators range from little ‘suitcase’ units that can easily be moved by one person and house all their moving parts in a clean and soundproofed casing, to larger types that have an open-frame design – this makes inspection and maintenance easier but increases noise. Larger units have carrying handles or wheels to move them.

With gasoline generators you may find a significant variance between the rated capacity (the electrical power the generator can generate continuously) and its peak capacity (which it can deliver momentarily to meet surging loads such as when an air-conditioning unit starts up) – this can be as much as 20 or 25% higher than the rated capacity. Many generators are sold and named after their peak capacity, so make sure that you’re buying a unit suitable for the loads you’ll be wanting to power with it.

Gasoline is not a stable fuel. As well as the fire risk of storing large quantities, it degrades with time. Old gasoline left in the fuel system of a generator can produce sludge and varnish, so when you need your generator the most it won’t work! Gasoline generators are ideal for occasional light-duty use but less suited for regular heavy duty purposes. Lower-cost portable generators may not produce power that is sufficiently consistent in voltage and frequency to run sensitive electronic equipment without going through an uninterruptable power supply or inverter.

2. Diesel Portable Generators

Diesel engines are heavier and more expensive than a gasoline engine of the same power. They are also creating significantly more noise – especially when air cooled as many small, lower-cost portable units are. Their advantages are that they are significantly more fuel-efficient than gasoline engines and much better suited to long period running at heavy or full load (although they can be damaged by long periods of low-load running). They also respond better to sudden load changes, and diesel generators usually have peak capacities much closer to their rated load.

Diesel fuel represents a much lower fire hazard when stored and does not degrade with time. Diesel engines also lack an ignition system. These factors mean that they can be relied on to start even after long period between uses. If your budget allows, a diesel portable generator is better suited to running large electrical demands in a home or business for long periods – days at a time.

Self-Contained Generators – 10kW to 75kw Output

For those who require more capacity and capability than is feasible with a portable generator, a self-contained generator is an attractive solution. While some are large industrial gasoline engines (often adapted to run on Liquid Natural Gas), most use diesel engines derived from those used in industrial equipment and commercial vehicles to deliver reliable, efficient and long-lasting power.

These units are built into self-contained weatherproof and acoustically-damped casings, often built to the dimensions of international shipping containers for easy transport. Although not easily mobile, they are usually mounted on steel box section runners so they can be moved by fork-lift trucks or loaders, and have attachments so they can be lifted into place by a loader crane. These units usually have an integral fuel tank sufficient for many hours of running time as well as fittings to draw fuel from a much larger external tank.

These units will be sized, designed and engineered for long periods (or even continuous) running at high loads. Their electrical equipment will respond quickly to changes in demand and will produce electricity with a well-controlled frequency and a very ‘clean’ sinewave, making them suitable for running electronic equipment and fully replacing mains power when needed.

Installed Generators – 50kW to 100kW+

For businesses and other locations that need dependable and self-contained back-up power, getting a diesel generator set permanently installed in your facility is the ultimate option. These will often be the same engine/generator sets as provided in self-contained units, although when installing them permanently this opens up the chance to fit larger units with more capacity. Instead of a moveable acoustic case, a permanently installed generator will sit on structural foundations in a dedicated room – often in the basement of a business or a bespoke outbuilding.

This is the most expensive way to give you backup power capability, but can also guarantee reliable high-capacity power that is entirely under your control. A fully installed generator can have equipment that will automatically start and connect the generator if mains power is lost, as well as systems that will maintain the oil and water temperature of the generator when it is not in use, reducing maintenance needs and ensuring that it can quickly develop full power if needed.