So, what is the difference between an air-cooled and a liquid-cooled generator? Both are automatic, permanently installed systems designed to restore power within seconds of an outage. With a few exceptions noted below, their operation and installation processes are very similar (see also: How Whole-Home Backup Generators Work).
The primary factor when choosing between air-cooled and liquid-cooled is power demand. Secondarily, noise level may also be an important consideration for some homeowners.
Both air-cooled and liquid-cooled generators operate on the same basic principle. A combustible engine powered by natural gas or liquid propane drives an alternator that produces electricity for your home during a power outage.
The difference lies in engine size and how heat is managed. The names describe exactly how each generator is cooled.
Air-cooled generators
Air-cooled generators use smaller engines, slightly larger than a riding lawn mower engine, and rely on a fan blowing air across the engine to regulate temperature. This design keeps the generator compact and cost-effective.
Generac air-cooled generators typically use 2-cylinder engines, either 816cc or 999cc, operating at 3,600 RPM, with output ranging from 14kW to 28kW.
Liquid-cooled generators
Liquid-cooled generators use much larger engines and circulate coolant through a radiator, much like a car engine. This allows them to handle higher electrical loads while running more efficiently and at lower engine speeds.
Generac liquid-cooled generators designed for residential use typically use 4.5-liter inline 4-cylinder engines, producing 22kW to 80kW, with larger models available beyond that range.
That single design difference affects capacity, sound levels, longevity, and installation complexity.
Air-cooled generators are the most common choice for residential use and work well for most homes.
They are typically a strong fit for homes in the 1,500 to 5,000 square foot range, though generator sizing depends more on electrical demand than square footage alone. With proper design, many air-cooled systems provide true whole-home backup.
Air-cooled systems can be paired with smart load management to prioritize essential equipment and prevent overload during high-demand moments. In homes with two electrical panels, a single air-cooled generator may power both panels, or in higher-demand situations, only the primary panel may be backed up.
They commonly support:
Liquid-cooled generators are built for higher demand and larger electrical footprints.
They are often selected for larger homes with multiple HVAC systems or properties with heavy motor loads. Generator sizing is driven more by power-hungry appliances than home size alone.
These systems provide more power capacity, which can reduce or eliminate the need for load shedding.
They commonly support:
The gas plumbing and electrical work are similar in nature for both generator types. Liquid-cooled generators require larger gas lines and heavier electrical wiring, but the overall installation process follows the same general steps.
Air-cooled generators can typically be moved and set in place by one technician using a specialized generator cart. It is installed on a pad approximately 4.5 feet by 2.5 feet, and usually requires a 40-inch gate or easement for access.
Liquid-cooled generators require heavy equipment such as a forklift or telehandler for placement. These units require a larger pad, typically 7 feet by 3.5 feet, and a gate or easement large enough for heavy equipment access, generally 9 feet or wider.
Many homeowners assume a larger generator must be louder. In practice, the opposite is often true.
Air-cooled generators operate at higher engine speeds, typically 3,600 RPM, which creates more mechanical noise and a sharper sound profile.
Liquid-cooled generators operate at 1,800 RPM, which is half the speed. Combined with:
…the result is often a lower-pitched, smoother, and quieter sound, especially noticeable during weekly exercise cycles.
Most of the cost difference comes from the generator itself, which can double or triple in price, along with larger concrete pads and the need for heavy equipment during installation.
Air-cooled generators are an excellent solution for most homeowners who want reliable whole-home backup power. Liquid-cooled generators are better suited for larger homes with multiple HVAC systems or higher electrical demand. The right choice is determined by a proper load calculation, fuel supply capacity, and site layout, not just square footage.
Contact Guardian Home Generators today for a hassle-free site assessment and quote!