Why the questions matter more than the price
Generator bids fail owners in a predictable way: the low number wins, and then the missing scope arrives as change orders — the second transfer switch, the permit fees, the commissioning visit, the gas-line upgrade. The defense is boring and effective: ask every supplier the same sharp questions, in writing, and compare the answers as carefully as the prices. A supplier who answers all twelve crisply is telling you something about how the project will go. So is one who doesn't.
The twelve questions
1. Is the quoted kW a standby (ESP) or prime (PRP) rating?
Under ISO 8528, a standby rating covers outage duty with limited annual hours; a prime rating is built for unlimited running and typically sits 15–20% lower on the same machine. Two bids quoting "150 kW" may not be quoting the same machine capability. The ratings guide explains the classes.
2. What does that rating become at my site — after derates?
Altitude and high ambient temperature reduce real output. Ask for the site-rated kW, not the brochure kW, and how it was calculated. A machine that clears your load by 4% on paper may not clear it in August.
3. Exactly what transfer-switch scope is included?
How many ATS, what amperage, what transition type, service-entrance rated or not, and who wires them. The ATS is one of the largest line items after the genset, and "ATS by others" in small print is a classic gap. Read the ATS guide before this conversation, and sanity-check sizing with the ATS sizing tool.
4. What is the fuel plan, in hours?
For diesel: tank size in runtime hours at my load, containment, fill and overfill protection, and who handles fuel testing later — the full picture is in the fuel storage guide. For gas: has anyone verified the meter and line can feed the generator's full demand at pressure, and who pays if they can't?
5. Who pulls the permits, and is that in the price?
Electrical, building, fuel, and any county environmental layer — with the drawings and cut sheets the reviewers will want. The permit process guide shows what "handled" should mean. If permitting is excluded, the bid isn't comparable to one where it's included.
6. Is startup and commissioning included — and NFPA 110 acceptance testing where it applies?
A generator isn't delivered, it's proven: factory-authorized startup, loaded testing, and for life-safety systems the acceptance test your AHJ will require. Commissioning on covered projects is a real budget line — see the cost guide.
7. Can the set accept my largest load step?
Motors and UPS rectifiers arrive in blocks, not ramps. Give suppliers your biggest simultaneous step — fire pump, chiller, elevator bank — and ask for the transient response: voltage and frequency dip, and recovery time. This is where undersized-on-paper machines get exposed.
8. What enclosure grade am I getting — noise and wind?
Sound attenuation in dBA at a stated distance, wind rating against your local design speed, seismic certification if your jurisdiction requires it. The enclosure guide translates the grades. "Weatherproof" is not an acoustic answer.
9. What does the warranty actually cover, for how long, and who performs the work?
Term in years and hours, what's excluded, whether the servicing dealer is local, and whether extended coverage exists. A warranty serviced from three states away is worth less than its paper.
10. What is your guaranteed service response time?
In writing: hours to a technician on site, parts stocking for my model, and emergency coverage during regional events — when every generator in the county needs attention at once. Pair this with what the maintenance contract includes and costs.
11. What is the lead time — from PO to commissioned?
Equipment lead time, and the real schedule driver: permitting and site work. Ask which is the critical path, and how the supplier's last three projects in this county actually ran.
12. What do I hold at handover?
O&M manuals, as-built one-line, permit closeouts, acceptance-test records, the maintenance log started, and a walkthrough for my staff — switch positions, alarm response, what to check weekly. If the answer is "the manual's in the cabinet," push.
Turning answers into a decision
Three practical rules:
- Same scope or no comparison. Normalize every bid to the same ATS count, tank hours, enclosure grade and commissioning scope before comparing a single dollar. The cheapest number in a stack of quotes is usually missing a line item, not beating the market.
- Get the derated, site-specific kW in the contract — not the model number's nameplate.
- Silence is an answer. A supplier who won't commit to response time or won't put permitting in scope has answered question 10 and 5 — just not the way you hoped.
Ask everyone at once
This list is exactly what the Project Board operationalizes: post your project once — industry, state, size or square footage, fuel preference, timeline — and it reaches dealers and contractors pre-scoped, with a recommended size and cost range attached, so the offers that come back are answering the same questions and comparable line by line. Prefer a direct conversation first? Request a quote, and bring this page.
Frequently asked questions
How many generator bids should I get?
Three comparable bids is the practical standard — enough to see the market, few enough to normalize scope honestly. Comparability matters more than count: five bids with five different scopes tell you less than three normalized ones.
What's the biggest red flag in a generator quote?
Scope silence — the quote that doesn't mention permits, commissioning, or the transfer switch details. Missing lines aren't savings; they're invoices that haven't arrived yet.
Should I buy the generator and installation from the same company?
Turnkey concentrates responsibility — one party owns the outcome, which matters most at 2 a.m. during an outage. Equipment-only can save money when you already have a strong electrical contractor engaged; see the cost guide for how the scopes split.
Answers touching code — restoration times, acceptance testing, permits, required runtimes — vary by jurisdiction and edition; verify the specifics with your AHJ and your engineer before you rely on them.