Standby Generator Installation: Process & Cost

Standby generator installation requires permits in virtually all US jurisdictions. You typically need a building permit, an electrical permit for the transfer switch and panel work, and a gas permit for the fuel line connection. Some areas also require a mechanical permit. Permit fees total $100 to $300 in most jurisdictions. Your generator installer handles the permit applications, but the permitting timeline is not within their control. Most jurisdictions take 2 to 4 weeks to review and issue residential generator permits. Some expedited permit programs exist in states with high outage frequency (Florida, Texas, the Southeast). In addition to permits, your utility must be notified before a generator is connected, to ensure the transfer switch is correctly installed so the generator cannot back-feed power onto the utility grid, which is dangerous for utility workers. Notify your utility company as part of the permit process.

The generator must be placed on a level, stable surface. Most standby generators sit on a concrete pad poured specifically for the installation. The pad dimensions match the generator footprint plus several inches of clearance around it. Concrete pad installation costs $300 to $600 for a standard residential generator. Some generators come with pre-formed composite pads at lower cost but less longevity. Placement rules apply: minimum 5 feet from any opening (door, window, or air intake), at least 5 feet from any propane or natural gas meter, and at least 18 inches from the home's exterior wall for most models. Check the manufacturer's specifications and local codes for exact clearances.

The automatic transfer switch (ATS) is the brain of the standby generator system. It monitors utility power continuously. When it detects an outage, it disconnects the home from the utility, starts the generator, waits for the generator to reach stable operating voltage and frequency, then switches the home's electrical load to the generator. When utility power returns, the process reverses automatically. The ATS is installed by a licensed electrician between the utility meter and your main electrical panel, or as a sub-panel protecting specific circuits. Two main configurations exist: a whole-house transfer switch that handles the entire electrical panel (required for a generator large enough to power everything), and a load-management transfer switch that manages priority circuits.

For a natural gas generator, a licensed plumber or gas line contractor runs a new gas line from the nearest branch of your home's gas supply to the generator location. The required pipe size depends on the generator's BTU demand and the distance from the supply. A 22kW generator running at full load consumes roughly 180 cubic feet of natural gas per hour, which requires a supply line sized to deliver that volume at adequate pressure. Most residential gas lines need to be upsized or run as a dedicated branch to meet this demand. Cost: $300 to $800 for a short run under 50 feet, $600 to $1,500 for longer runs. For propane generators, a 250 to 500-gallon propane tank is installed near the generator. Tank installation by the propane supplier costs $800 to $2,000.

The electrical work includes wiring from the generator to the ATS, connecting the ATS to the main panel, running a low-voltage control wire from the ATS to the generator (for the automatic start signal), and installing any load-shedding relays if the system uses load management rather than whole-house coverage. For whole-house systems, the main panel may need to be reconfigured or a new sub-panel installed. Conduit routing from the generator to the ATS location adds labor time, particularly if the run requires penetrating the foundation or routing through finished spaces.

After all components are installed and inspections pass, the installer performs a commissioning test. The generator is started, run up to operating temperature, loaded with a test load, and verified to transfer correctly from the ATS. The automatic exercise cycle is programmed (most standby generators run themselves for 20 minutes once a week to keep the battery charged and lubricate the engine). The installer shows you the key operational controls, explains how to check oil level and battery condition, and provides the first maintenance schedule. Most manufacturers require a first service at 20 to 30 hours of operation. Service intervals after that are typically every 100 to 200 hours or annually, whichever comes first.