Find a commercial generator service
A facility manager's vetting checklist: load studies, NFPA 110 testing schedules, maintenance contract red flags, and the questions that separate genset pros from truck-and-ladder outfits.
First: know your own numbers
Before you call anyone, walk in with two figures. One: your actual running load — not the generator's nameplate. A 300 kW unit loafing at 40 kW is a wet-stacking diesel waiting to foul. Two: your largest single motor start — chiller, fire pump, elevator — because surge, not steady state, sizes the installation. Our generator size calculator gets a facility list into rough shape in ten minutes; a contractor should then perform a proper load study with a logger before quoting anything. A contractor who quotes off a nameplate walk-through without a load study is selling you a unit, not a system.
The testing schedule a real service follows
| Interval | What gets done |
|---|---|
| Weekly | Visual inspection: fluid levels, block heater, battery charger, no active alarms |
| Monthly | Exercise under load — 30 min at ≥30% nameplate (NFPA 110), transfer switch operation check |
| Quarterly | Oil sampling, coolant condition, battery load test, fuel sample (water/microbial check on diesel) |
| Annual | Load-bank test 2–4 hrs at rated load, full PM service, ATS contact inspection, fuel polishing if indicated |
NFPA 110 governs emergency/standby systems; your insurer, fire marshal, or accreditation body (hospitals: Joint Commission) may add requirements. Every visit should land in a written log you can hand an inspector.
Contract red flags
- Load-bank testing billed as a surprise add-on — it's the annual core of diesel PM, not an upsell.
- No response-time commitment in writing. "24-hour emergency service" means nothing without a contractual SLA.
- They don't touch transfer switches. The ATS is the single most-failed component in standby systems; a service that only turns wrenches on the genset leaves you exposed.
- No compliance documentation. If their visit reports wouldn't satisfy your fire marshal or insurer, you're paying for logs you can't use.
- Fuel maintenance never mentioned. Stored diesel degrades in 6–12 months; polishing and biocide are recurring line items, not emergencies.
The vetting questions
- Are your technicians EGSA-certified or factory-trained on our unit's brand?
- Will you perform a load study before recommending any change?
- Is load-bank testing included in the annual contract price?
- What's the contractual emergency response time?
- Do you service automatic transfer switches and ATS controls in-house?
- Do you provide AHJ/insurer-ready compliance documentation?
- Can you support a maintenance account across multiple facilities, or is this a one-truck operation?
Need a licensed commercial generator contractor for install, transfer switch work, or a maintenance contract? This slot is reserved for a vetted local operator.
Managing your own smaller standby unit between service visits: load-bank portable testers, battery load testers, and fuel test kits on Amazon cover the monthly basics.
FAQ
What does commercial generator service cost?
Typical U.S. contracts run roughly $1,500–$5,000/year for a mid-size diesel standby unit including monthly PM, scaling with kW class, fuel type, and whether load-bank testing is bundled. Emergency calls outside contract run $150–$300/hour. Get three quotes and compare line items, not totals — the cheap contract often excludes load-bank and ATS work.
Install or replace: what does the project involve?
Site survey and load study, permitting, a poured pad, fuel supply (sub-base tank or utility gas), wiring through a transfer switch, and commissioning with a witnessed acceptance test. Budget weeks-to-months for permitting and inspection depending on jurisdiction — the equipment is the fast part.
Can we service in-house instead?
Small facilities with a trained maintenance tech can handle weekly/monthly checks, but most commercial operators outsource: the annual load-bank test, ATS service, and fuel polishing need equipment and certifications most shops don't carry, and the compliance log is the real deliverable.