Generator maintenance: don't skip it.
Standby generators sit idle most of the year, then must start and run reliably during outages. Regular maintenance is essential — neglected generators fail at the worst time.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Industrial generator maintenance scope: quarterly inspections (visual, fluids, batteries, starting circuit), annual full service (oil and filter change, coolant check, ignition system check on natural gas units, fuel system check on diesel, comprehensive functional test), load bank testing every 3 years (full load operation test verifying capacity), as-needed repairs. Marin commercial maintenance contract typical $1,500-$5,000 annually depending on generator size and scope.
01Why generators need scheduled maintenance.
Generators have characteristics that make them prone to neglect: they sit idle 99%+ of the time, with weekly self-exercise being the only routine operation; they don't show 'check engine' warnings to operators; failures only manifest during actual outage operation. This combination means neglected generators can pass weekly self-exercise (which only runs the engine briefly under no load) yet fail when called on for sustained outage operation. Scheduled maintenance catches developing problems before they cause outage-day failures.
Common issues caught by maintenance: battery degradation (most common cause of generator failure — starting battery weak from age and infrequent deep discharge), fuel system contamination (diesel fuel degrades over 6-12 months in storage, requiring polishing or replacement), oil degradation (oil ages even when engine isn't running, requires annual change), coolant breakdown, electronic control issues, fuel filter clogs, exhaust system problems. Each is preventable with proper maintenance schedule.
02Maintenance components.
Quarterly inspection
Visual inspection of generator and enclosure, fluid level checks (oil, coolant, fuel, hydraulic if applicable), battery condition test, terminal cleaning, control panel function check, generator log review (run hours, run count). 1-2 hour visit. Documented inspection report.
Annual full service
Oil and filter change, coolant condition check (refresh every 2-3 years), air filter inspection/replacement, fuel filter replacement (annual on diesel, less frequent on gas), battery load test, governor inspection, transfer switch inspection, ATS testing. 4-8 hours typical.
Load bank test
Generator operated at full rated load using portable load bank (or building load if appropriate). Verifies generator can actually deliver nameplate capacity. Recommended every 3 years per NFPA 110 for emergency systems. Half-day to full day exercise.
03What we offer at Towery Electric.
Maintenance contracts: we offer quarterly, semi-annual, or annual scheduled maintenance contracts for Marin commercial generators. Contracts typically include all scheduled maintenance, priority response for emergency repairs, parts pricing at near-cost, and documentation appropriate for code compliance (NFPA 110 logs for emergency systems). Pricing scales with generator size and frequency: small commercial annual visit only ~$800; larger commercial with quarterly visits $3,000-$5,000.
Emergency response: commercial generators sometimes fail during actual outages — exactly when they're needed. We respond to emergency calls for generator failure during outages with priority same-day or next-day service depending on situation. Repairs typically include battery replacement, fuel system service, control panel troubleshooting, sometimes engine repair (coordinated with engine manufacturer support). Most failures are recoverable on-site within hours.
Common questions.
How often should I test the generator beyond weekly self-exercise?
NFPA 110 (emergency power) recommends monthly under-load exercise (30+ minutes at 30%+ load) plus annual load bank test. Weekly self-exercise (factory default) is too brief and at no-load — doesn't verify the generator can actually carry load. We recommend monthly extended exercise under building load (via ATS) plus periodic load bank for thorough verification. Most Marin commercial owners run monthly extended exercise; load bank testing handled through maintenance contract.
How do I know if my generator is well-maintained?
Indicators: documented maintenance log with regular entries, recent oil and filter change history, recent battery test or replacement record, recent annual service report, no unresolved findings from prior inspections. New owners of commercial properties with existing generators: review maintenance records during due diligence. No records means assume long-neglected and budget for catch-up service. Catch-up service often $2,000-$8,000 for previously-neglected commercial generator.
Can I do maintenance myself?
Visual inspection and fluid checks: yes, suitable for facility manager or maintenance staff. Oil change and filter service: possible but requires proper procedure (manufacturer specs vary). Battery service: possible. Load bank testing and electrical system maintenance: requires specialized equipment and training. Most commercial owners contract maintenance to qualified service providers (us or other specialized vendors) for cost-effectiveness and documentation.
What if my generator hasn't been maintained in years?
Catch-up service: comprehensive inspection identifying all developing issues, oil/coolant/fuel system service, battery replacement (almost certainly needed), control system check, load bank test if equipment supports it. Cost $2,000-$8,000 depending on findings and remediation needed. Sometimes catch-up reveals problems requiring significant repair or replacement; sometimes catch-up restores generator to reliable service for years more. Worth doing before next outage event.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
Talk to a licensed electrician in Marin.
Family-run, C-10 #989290, 20+ years in the trade. Honest scoping, fair pricing, work that lasts.