Why three quotes for the same work come back thousands apart

Line the three up on five rows, and the gap usually explains itself

Take a sheet of paper and give it five rows: the size specified; what is included besides the equipment; what is excluded in writing; what happens at handover; and the warranty, with who honours each part of it. Fill in all three columns. In our experience the largest single gap is almost always row two or row three.

The five things most often in one quotation and not the others: duct remedial work; a new thermostat and controls; a condensate pump or a new drain route; electrical — a disconnect, a whip, sometimes a breaker; and permit and inspection where the work requires it. Any one of those is a meaningful sum, and the cheaper quotation frequently does not exclude them in writing either, which is worse than excluding them.

Then ask each firm the same single question: “what is in the other two quotations that is not in yours?” A firm that knows its market can usually tell you, and how they answer tells you more than the number does.

Stop comparing prices. At least one of them did not calculate.

Two competent load calculations on the same house land in the same place. If three quotations name three different sizes, somebody has used the tonnage already installed, or floor area, or a rule of thumb — and the price comparison is meaningless until you know which.

Ask each firm for the calculation with its assumptions: the glass area and orientation, insulation levels, air leakage, shading, occupancy, and what the ductwork can carry. Not the summary sheet with a total on it — the inputs. If those differ between firms, the argument is about the inputs rather than about the equipment, and that is an argument you can actually resolve.

And be suspicious of the largest, not the smallest. Oversizing is the safer-sounding mistake and the more common one: a system with too much capacity cools without drying, short-cycles and wears out early. “We always go a half ton bigger to be safe” is not a calculation, it is a habit.

Worry about the installation and the warranty terms, not the badge

Within a given class, the differences between the major manufacturers matter far less to how a system performs than the quality of the installation does. Charge, airflow, duct condition and correct sizing account for more of the outcome than the name on the cabinet, and every serious person in this trade knows it.

What is genuinely worth comparing: the length of the parts warranty and what registration it requires; whether labour is covered and for how long and by whom; whether the contractor is an authorised servicer for that brand, because some manufacturers restrict parts cover; and how easily parts reach this area, which decides how long you wait when something fails in August.

About efficiency ratings: a higher rating is a real thing, and what it is worth to you depends on how much you actually run the system, on your ductwork and on your rate. Ask anyone quoting a payback period to show the arithmetic and the assumptions. We will not give you a percentage saving without measuring, and neither should anybody else.

Take the one that includes it seriously — it may be the only complete quotation

A quotation that includes duct remedial work is not an upsell by default. In this housing stock it is frequently the only one that reflects what the building actually needs, and the two cheaper ones are quoting for equipment in a system that cannot carry it.

How to tell which it is: ask the firm that included it for the measurement that justified it — static pressure, airflow at the registers, return capacity. Numbers, taken at your house. Then ask the two that did not include it what your static pressure was. If they do not know, they did not measure, and their price is for a different job rather than a better deal.

And ask what happens if it turns out to be needed. Get that in writing before you choose. “We would look at it then” means a change order at the point where the old system is already out.

Find out why, because the reason is either very good or very bad

A firm that can start on Monday in the middle of a heat spell is either well organised with stock on the shelf, or it has an empty diary. Both are possible and they point in opposite directions.

The good version: they hold common equipment rather than ordering it per job, they schedule properly, and they have a crew free because a job finished early. Ask directly: is the equipment in stock, and is the crew that would do my job the same crew that does everything else?

The version worth pausing over: speed offered as the reason to choose. If the pitch is that they can do it tomorrow and the price only holds if you say yes now, those two things together are a sales structure rather than a schedule.

And if you genuinely have no cooling and it is 95 degrees, that is a real constraint and nobody should pretend otherwise. Get the failed system repaired if it can be repaired, even temporarily, and make the replacement decision in a week when you are not making it in a hot house.