Generator glossary
The terms installers use in quotes and spec sheets, explained in plain English.
- Air-Cooled vs. Liquid-Cooled
- Air-cooled generators use a fan to cool the engine and are the standard choice for most residential systems up to about 26 to 28 kW, depending on the brand (Generac's air-cooled line goes to 28 kW). They're less expensive and adequate for typical home backup needs. Liquid-cooled generators use a radiator-based cooling system similar to a car engine, allowing for larger capacity than air-cooled units, at a higher price point. Most whole-home residential installations use an air-cooled unit; liquid-cooled units become more common for larger homes or light-commercial applications.
- Related: Standby Generator, Run Time
- Automatic vs. Manual Transfer Switch
- An automatic transfer switch (ATS) detects a power outage and starts your generator/switches your home over within seconds, with no action needed from you. A manual transfer switch requires you to physically flip the switch and start the generator yourself. Nearly all whole-home standby generator installations use an automatic transfer switch; manual switches are more common with portable generators.
- Related: Transfer Switch, Portable Generator
- Backfeed
- The dangerous condition where a generator connected without a proper transfer switch sends electricity backward through your home's wiring and out onto the utility grid. Backfeed can seriously injure or kill utility line workers who assume the grid is de-energized during an outage while making repairs, which is why a code-compliant transfer switch is a non-negotiable safety requirement for any permanently connected generator, not just a convenience feature.
- Related: Transfer Switch, Automatic vs. Manual Transfer Switch
- Cold Start Kit
- An optional add-on, mainly relevant in colder climates, that includes a battery blanket and/or engine block heater to help a standby generator start reliably in freezing temperatures. Less commonly needed in Texas and Florida installations covered by this directory, but worth asking about if your property is in a region that sees regular hard freezes.
- Related: Standby Generator
- Decibel (dB) Rating
- A measurement of how loud a generator is while running, typically listed by manufacturers at a standard distance of 23 feet. Manufacturers rate residential standby generators at roughly 61 to 70 dB(A) at 23 feet while running (Generac's air-cooled models 61 to 67, Kohler's 20 kW 20RCA 70), and lower during the weekly exercise. For comparison, a normal conversation is about 60 dBA. Lower dB ratings matter most when the installation site is close to a bedroom window, a patio, or a neighboring property line, since local noise ordinances in some cities can also factor into equipment placement decisions during permitting.
- Related: Standby Generator, Air-Cooled vs. Liquid-Cooled
- EGSA (Electrical Generating Systems Association)
- A trade association for the on-site power generation industry, including generator manufacturers, distributors, and installation professionals. EGSA membership and certifications (such as its Certified Generator Technician program) are sometimes used by installers as a credential alongside their state electrical contractor license, though the electrical contractor license itself, not EGSA membership, is the legal requirement to perform installation work.
- Related: NEC (National Electrical Code), Standby Generator
- kW vs. kVA
- kW (kilowatts) measures real, usable power: the number generator brands advertise and the figure used for sizing your system. kVA (kilovolt-amperes) measures apparent power, a related but slightly larger number due to a factor called power factor. For most residential standby generators the two numbers are close enough that kW is the only figure you need to pay attention to when comparing units or sizing a system.
- Related: Load Calculation, Standby Generator
- Load Calculation
- The process a licensed electrician uses to determine how much electrical capacity (measured in kW) your home actually needs from a generator, based on the specific circuits and appliances you want backed up during an outage, not a square-footage estimate. A proper load calculation reviews your electrical panel's circuit list and accounts for both continuous loads (refrigerator, lighting) and high-draw starting loads (AC compressors, well pumps) to recommend an appropriately sized system.
- Related: kW vs. kVA, Standby Generator
- NEC (National Electrical Code)
- The National Electrical Code is the model electrical safety standard adopted, often with local amendments, by most US states and cities to govern electrical installations, including standby generator connections, transfer switch requirements, and grounding. Local building departments enforce their adopted version of the NEC through the permit and inspection process, which is why permit requirements can vary somewhat between cities even though they're all ultimately based on the same national code.
- Related: Backfeed, Transfer Switch
- Portable Generator
- A gasoline-, propane-, or diesel-fueled generator that is not permanently installed. It must be manually set up, fueled, and started when a power outage occurs, and is typically connected to specific appliances via extension cords or, with a manual transfer switch, to a subset of your home's circuits. Portable generators are generally lower-cost than standby systems but require active management during every outage and must always be run outdoors due to carbon monoxide risk.
- Related: Standby Generator, Automatic vs. Manual Transfer Switch
- Run Time
- How long a generator can operate continuously on a given fuel supply. Natural-gas standby generators have effectively unlimited run time as long as utility gas service continues, since they draw directly from the gas line rather than an on-site tank. Propane and diesel units are limited by their tank size, and a larger on-site propane tank extends run time but requires more space and periodic refilling. Portable gasoline generators typically have the shortest run time per tank and require the most frequent manual refueling.
- Related: Standby Generator, Portable Generator
- Standby Generator
- A permanently installed generator, connected to your home's electrical panel through an automatic transfer switch and fueled by natural gas or propane, that starts automatically within seconds of a power outage. Unlike a portable generator, it requires no manual setup during an outage and typically remains outdoors on a permanent pad or mounting bracket. This is the equipment type this directory focuses on.
- Related: Portable Generator, Transfer Switch, Automatic vs. Manual Transfer Switch
- Transfer Switch
- A device installed between your utility meter and your home's electrical panel that switches your home's power source from the utility grid to your generator during an outage, and back again once utility power is restored. Required by electrical code for any permanently-installed standby generator. Without one, backfeeding your generator's power into the grid is a serious safety hazard for utility line workers.
- Related: Automatic vs. Manual Transfer Switch, Backfeed, Standby Generator
- Weatherproof Enclosure
- The outdoor housing that protects a standby generator's engine and electrical components from rain, sun, and debris while it sits outside year-round. Manufacturers rate enclosures for specific weather conditions, and in coastal or hurricane-prone areas like Miami and Orlando, installers often need to confirm wind-rating and, in some jurisdictions, provide NOA (Notice of Acceptance) documentation as part of the permitting process.
- Related: Standby Generator, Decibel (dB) Rating
- Whole-House vs. Partial-House Backup
- Whole-house backup means every circuit in your home stays powered during an outage, requiring a larger generator (typically 22 kW or more) sized to handle your home's full simultaneous electrical load. Partial-house (or "essential circuits") backup powers only a selected subset (refrigerator, well pump, some lighting, one AC zone) using a smaller, less expensive generator (commonly 10 to 14 kW) and a load-management or circuit-selection setup at the transfer switch. Most residential installations fall somewhere between these extremes, tailored to which circuits actually matter to the homeowner.
- Related: Load Calculation, Standby Generator