The equipment is broadly comparable across the major manufacturers. The installation and the service relationship are where the differences are.
Ask for the load list
The single most revealing request.
An installer who has calculated the load produces a list of circuits with running and starting watts, the shedding arrangement, and the generator's derated output at your elevation.
One who has not will name a kW figure and a house size. That is a product recommendation, not a design.
Ask what happens to the gas supply
A standby generator is a large gas load, and existing meters frequently cannot carry it.
The right answer names the generator's demand in cubic feet per hour, states the existing meter's capacity, and says whether the utility has been contacted.
An installer who has not considered it will find out after the pad is poured.
Ask about the transfer switch neutral
Whether the generator is connected as a separately derived system, and whether the switch breaks the neutral.
There is a correct answer for each combination of equipment, and an installer who works with this daily gives it immediately. Hesitation here is informative.
Ask about service after installation
Who does the annual maintenance, and are they local.
What the response time is during a widespread outage, when every customer calls at once.
Whether they stock parts for the brand they are selling.
A generator is a machine that has to start unattended after months of sitting. The service relationship is most of what determines whether it does.
Ask about permits
Electrical and gas permits, and the inspections.
An installer proposing to work without them is proposing that the household carry the disclosure problem and the insurance risk.
Ask about the commissioning tests
Gas pressure at the generator under load, which proves the supply.
A transfer test with the house's real loads on.
A shedding test, confirming the priority order behaves as designed.
Those three take half an hour at the end of the job and they are what distinguishes a commissioned installation from a delivered one.
Check independently
Licence and insurance, from the issuing body. Manufacturer dealer status, which is generally required for the warranty. References from installations several years old rather than last month — a generator's problems appear with time, not at handover.
What not to choose on
Brand loyalty. The major manufacturers all make competent air-cooled units in the residential range.
The headline kW alone, which as covered elsewhere depends on fuel, elevation and temperature.
Price alone, where the difference turns out to be the gas work or the permit.
After a regional outage
Demand spikes and every dealer is booked for months. Quality of installation falls when crews are working flat out, and prices rise.
The households that end up with good installations are the ones that arranged them in a quiet period. That is worth knowing in the week after an outage, when the temptation to sign the first available quote is strongest.
The maintenance agreement
Most dealers offer an annual agreement covering the scheduled service plus a functional test, and sometimes priority response during an outage.
Whether it is worth the price depends on what the same visits cost separately, and on whether the household will otherwise arrange them. A generator that goes unserviced is an expensive object that will not start, so the honest question is not the price but whether the alternative actually happens.
Check specifically what is included — oil and filters, plugs, battery test, and whether the battery itself is covered.
Getting three quotes
Give each installer the same information: the appliance list, the fuel available, the preferred generator location, and whether the backup is whole-house or essential circuits.
Quotes built on the same brief are comparable. Quotes built on each installer's own assumptions are three different projects, and the cheapest is usually the one that assumed the least.