Should I repair or replace an old standby generator?

Repair an old standby generator when the engine and alternator are sound and the problem is a part. Replace it when the expensive core has failed, when parts and dealer support for your model have dried up, or when the unit no longer fits what your house needs. The deciding step is a written diagnosis from a qualified technician that names the failed part, the repair cost and the condition of everything else.

Start with a diagnosis, not a sales pitch

Many generators that "need replacing" have an ordinary fault. Kohler's service manual tells technicians: "When troubleshooting, always check for simple problems first."^[1] Its list of common problems is loose connections or damaged wiring, a dead battery, an inadequate fuel supply, a fault shutdown and incorrect controller settings.^[1] Its troubleshooting chart for engines that will not crank or will not start runs through weak or dead batteries, poor battery connections, spark plugs, a clogged air cleaner, a closed fuel valve or empty propane tank, the starter relay and the starter itself^[1] before it reaches the engine and alternator.

Some faults are even cheaper than parts. Kohler says nuisance shutdowns seen with earlier firmware versions of one of its controllers are eliminated by updating the firmware.^[1] Ask the technician to read the controller's fault and event history before quoting.

If a company recommends replacement without telling you what failed, get a second opinion. For the common no-start causes, see why a standby generator won't start.

When repair is the better value

Repair usually makes sense when:

• the failed part is a wear item or accessory: battery, charger, spark plugs, air cleaner, starter, fuel valve or regulator, a sensor or a relay
• the engine has good oil pressure, starts and runs smoothly once the part is fixed, and has a reasonable number of run hours for its size
• the alternator tests healthy. Kohler notes that "Under normal operating conditions the generator set alternator does not require scheduled service,"^[1] and its schedule calls for measuring the alternator windings' insulation resistance every 3 years, which Kohler marks as authorized distributor/dealer only.^[2] A good reading is a reason to keep the unit
• parts for your model are still available and a dealer will support it
• the unit still covers the circuits you need in an outage

A well-kept generator lasts longer. Kohler's manual tells owners to have an authorized distributor/dealer service the generator set at the designated intervals in the service schedule for the life of the generator set.^[2] A unit with a full service record is a better candidate for repair than one that has been ignored. See what a standby generator service visit includes.

When replacement is worth pricing

The core has failed. A seized or badly worn engine, or a failed alternator, is usually among the costliest repairs a generator can need. Ask for the repair quote and a replacement quote side by side.

Parts and support are gone. Manufacturers move on. Kohler's installation manual for its current home models lists an earlier model as no longer available and notes that one of its controllers has been discontinued.^[3] Ask the dealer whether parts for your model, and especially its controller, are still made. Generac says its Authorized Service Centers provide parts, service, and information on Generac equipment, regardless of where it was purchased,^[4] so a Generac owner can ask any of them.

Repairs keep coming. Several repairs in a short span, each on a different system, point to a unit at the end of its life.

Your needs have changed. A heat pump, a well pump, an EV charger or a home office can change what you need in an outage. Generac notes that "There are many factors that impact the generator sizing and power needs for your home,"^[4] and sizing is the dealer's job. Remember, too, that "The backup generator is designed as a backup to utility power only and should not be used as a primary power source."^[4]

Check the warranty first

Before you pay for anything, check whether the unit or the part is still under warranty. Any Authorized Generac dealer can perform warranty service.^[4] Generac's 5-year warranty applies to a unit bought and installed through one of its dealers and is applied after installation and activation.^[4] Find your purchase paperwork and the serial number on the nameplate, and ask the dealer to look up the coverage.

What replacement costs

For a sense of scale, when we checked on October 27, 2026, Generac's website listed its 22kW WiFi-enabled home standby generator starting at $6,119.00 and its 14kW Guardian Series unit starting at $4,569.00.^[5] That is equipment only. Generac says the cost of installation is determined by the dealer and will vary based on several factors,^[4] and a replacement can need a new pad, transfer switch, fuel line or wiring. For ongoing costs, see how much standby generator service costs in Virginia.

A new unit is installed to its own manual and to current code, not the old one's. In Kohler's installation manual, the required distance from a structure depends on state and local codes,^[3] and furnace and similar air intakes must be at least 10 feet from the exhaust end of the generator.^[3] An old unit's spot may not meet a new unit's rules.

Permits apply to replacement. The USBC requires a permit before work on electric wiring, fuel supply systems or any equipment regulated by the code,^[6] and for emergency equipment replacement the application can be filed by the end of the first working day after the work starts.^[6]

Who to hire in Virginia

A standby generator touches two licensed trades. Electrical contractors (ELE) cover the construction, installation, repair, maintenance, alteration, or removal of electrical systems.^[7] Gas fitting contracting (GFC) covers the installation, repair, improvement, or removal of gas piping and appliances annexed to real property,^[8] and liquefied petroleum gas contracting (LPG) covers the piping, fixtures and appliances that use liquefied petroleum gas.^[8] A solar or battery installer is not automatically qualified: the alternative energy system specialty does not include the installation of emergency generators powered by fossil fuels.^[8]

The licence class must fit the contract value: Class C covers a single contract over $1,000 but less than $30,000, and Class B covers $30,000 or more but less than $150,000.^[9] Check the licence before you sign.

When to call a licensed pro

Call as soon as the generator fails a weekly exercise, shows a fault you cannot explain, leaks oil or fuel, or will not carry the house in an outage. For the decision itself, DPOR advises that you get at least three written bids or estimates using identical plans and specifications.^[10] Ask each company to quote both the repair and a replacement, with the failed part named, the unit's run hours and the parts availability for your model in writing. Keep the deposit modest: DPOR's rule of thumb is an initial deposit of no more than 10% of the total price or $1,000, whichever is less.^[10] Virginia law requires all licensed contractors to provide a written contract for residential work.^[10]

Browse generator repair and generators and backup power, find electricians in Blacksburg, or read more electrical repair answers.

To get your generator diagnosed, describe the job once and licensed local businesses quote the repair, the replacement, or both.