Two contractors walk through the same Denver basement in the same week. One hands you a single page with a model number and a total. The other hands you four pages with line items, a permit fee, a labor warranty and a commissioning checklist. The second number is higher. Most people assume they’re looking at the same job priced differently.
They’re usually not.
A replacement estimate is a scope document. It describes what will physically happen in your house, what equipment will be installed, what permits will be pulled and what happens when something fails in year three. When two bids differ by thousands, the difference is almost always sitting in what one of them didn’t write down. L & L Heating and Air Conditioning has been writing these documents across the Front Range for more than three decades, and what follows is how to read one line by line.
This applies to a furnace replacement, an air conditioner replacement, or both at once. The shared items come first, then the equipment-specific sections.
The Shared Core: What Every Replacement Estimate Should Contain
Complete Model Numbers, Not Just a Brand
You want the full alphanumeric model number for every piece of equipment, plus the AHRI reference number if the system is a matched pair. A quote that says “96% furnace, 80,000 BTU” is not specific enough to compare or to hold anyone to. Model numbers let you verify capacity, efficiency rating, stage count and warranty terms yourself.
Watch for the word “or equivalent.” That phrase gives the installer permission to substitute, and the substitution never goes up.
Matched Components
This is the item most commonly fudged on air conditioning quotes and it matters enormously. An outdoor condenser has to be matched to a specific indoor coil to hit its rated efficiency. Replacing the condenser while leaving a fifteen-year-old coil in place produces a system that performs nothing like the label. If the quote lists a condenser and no coil, ask directly whether the existing coil is being reused and whether the pairing is AHRI certified.
The furnace equivalent is the blower. A two-stage or modulating furnace needs its matched control board and thermostat to do anything more than run at full output.
Load Calculation
The estimate should state that a Manual J load calculation was performed, or that one will be, and the resulting number should drive the equipment size. At Denver’s elevation this isn’t paperwork. Gas furnaces lose roughly 4% of rated output per 1,000 feet of elevation, so sea-level sizing charts produce undersized equipment here. Our guide to high-altitude furnace sizing covers why this is non-negotiable on the Front Range.
An estimate that sizes the new system by matching the old one is guessing, and it inherits whatever mistake was made last time.
Venting, Gas and Electrical Work
Named explicitly, with materials and routing:
- Venting. If you’re going from an 80% furnace to a 96%, the estimate must include new PVC intake and exhaust, the route it will take, and any patching of the exterior penetration. It should also address the water heater if it currently shares a chimney with the furnace, because removing the furnace from that flue can leave the water heater venting into a chimney now oversized for it.
- Gas. Any resizing, new branch runs, sediment traps, or shutoff replacement.
- Electrical. Dedicated circuit, service switch, whip and disconnect for AC work, and panel capacity if it’s marginal.
Vague phrasing like “modify venting as needed” is a blank check pointed at you.
Permit and Inspection
Front Range jurisdictions require a permit for equipment replacement. The estimate should name the fee and state that the contractor pulls it. If the homeowner is expected to pull their own permit, that is a significant signal about how the company operates, and it shifts liability onto you. Our article on how to avoid HVAC inspection failures covers what inspectors actually look for.
Startup and Commissioning
This is the section that separates an installation from a delivery. A complete estimate specifies that the crew will:
- Set and verify manifold gas pressure
- Measure temperature rise and confirm it falls inside the nameplate range
- Measure external static pressure across the system
- Confirm the altitude derate is correctly applied
- Verify combustion and check for spillage
- Weigh in refrigerant charge by manufacturer specification on AC work, not by gauge pressure alone
- Confirm airflow in CFM per ton
- Program and test the thermostat through a full cycle
Equipment that’s installed but never commissioned will run. It just won’t deliver the efficiency you bought, and the failure is invisible until the utility bill arrives.
Labor Warranty Versus Parts Warranty
These are two different promises from two different parties and quotes routinely blur them.
Parts warranty comes from the manufacturer. It typically covers the heat exchanger for a long term and other parts for a shorter one, and it usually requires registration within a set window after installation, often 60 or 90 days. If nobody registers it, you silently drop to the base term. Ask who registers it.
Labor warranty comes from the contractor. It covers the cost of the technician’s time to diagnose and replace a part that’s under manufacturer warranty. Without it, a covered part failure in year four still generates a service bill. Labor warranties commonly run one to ten years and the length is a real differentiator between bids.
A quote advertising a “10 year warranty” without specifying which one is describing the manufacturer’s parts coverage, which every contractor selling that brand offers identically. It is not a competitive advantage. The labor term is.
Exclusions and Allowances
Read this section first, honestly. Common exclusions worth flagging:
- Duct modification or replacement
- Asbestos or unexpected material abatement
- Drywall repair and paint after venting penetrations
- Electrical panel upgrades
- Chimney relining
- Code corrections discovered once the old unit is out
An allowance is a placeholder dollar amount for work that can’t be scoped until demolition. Allowances are legitimate. Undisclosed allowances are how a $9,000 job becomes a $13,000 job on day two. Ask what happens if the allowance is exceeded and get the answer in writing.
Payment Terms, Timeline and Cleanup
Deposit amount, payment schedule, expected duration, who hauls the old equipment, and what protection goes down on your floors. If you’re financing, the terms should be separate from the scope. Our HVAC financing page explains how monthly payment options work, subject to credit approval.
Furnace-Specific Line Items
When the quote is for heating, look additionally for:
- Burner staging stated explicitly. Single-stage, two-stage or modulating, because it changes both price and comfort.
- Blower type. PSC, constant torque or true variable speed.
- Condensate handling. High-efficiency furnaces produce water. The quote should specify a gravity drain or a condensate pump, and where the water goes.
- Combustion air. In tight or finished basements, the furnace needs a verified air supply. Our article on combustion air in older Denver homes explains why this gets overlooked and what it causes.
- Return air. Undersized returns are common in older Denver housing stock and they will wreck a new furnace’s performance. See why return air sizing is crucial in Denver.
- Filter rack and filter size, including whether a media cabinet is being added.
Air Conditioning Specific Line Items
When the quote is for cooling:
- Refrigerant type and line set disposition. Will the existing line set be reused, flushed, or replaced? Reusing a line set that carried a different refrigerant without proper flushing causes problems that surface later.
- Indoor coil, as covered above.
- Condenser pad and clearances.
- Disconnect and whip.
- Charge verification method, weighed in per manufacturer spec.
- Condensate drain and secondary pan if the air handler sits over finished space.
If you want the day-of picture rather than the document, our AC installation preparation checklist walks through what actually happens once the crew arrives.
How to Compare Two Bids That Look Nothing Alike
Put them side by side and normalize before you compare totals.
- Match the equipment tier first. An 80% single-stage furnace and a 96% two-stage furnace are not competing products. Compare like to like, or accept that you’re choosing between two different purchases.
- Add the missing scope to the cheaper bid. If bid A includes new PVC venting and bid B doesn’t mention venting while quoting a condensing furnace, the venting still has to happen. Write in a realistic number and re-total.
- Compare labor warranty terms as years, side by side.
- Check whether both include permit and commissioning. If one doesn’t, that’s not savings, it’s omitted work.
- Read both exclusion lists. The bid with the longer exclusion list may be the more honest document.
- Ask each contractor the same question: “What could change this price once you open it up, and by how much?” The answer tells you more than the quote does.
If after normalizing the bids are still far apart, the remaining gap is usually labor rate, crew size, and how much time is budgeted for the job. Faster is not always better on a job where commissioning determines whether the equipment works as sold.
What This Page Doesn’t Cover
Total prices and equipment ranges are their own subject, and we’ve written them up separately in what a furnace replacement actually costs in Denver. The questions to ask a contractor before you ever get to a written quote, including licensing, subcontracting and permit handling, are covered in our guide to vetting an HVAC installer. And the broader case for why the quality of the install outweighs the equipment on the label is made in the importance of professional HVAC installation.
Frequently Asked Questions About HVAC Estimates in Denver
At minimum: complete model numbers for all equipment, the load calculation basis for sizing, venting and gas and electrical scope, permit and inspection, startup and commissioning steps, separate labor and parts warranty terms, a written exclusions list, payment terms and timeline. Anything less is a price, not an estimate.
Usually scope rather than markup. One quote includes venting conversion, return air correction, permit, commissioning and a multi-year labor warranty; the other includes a box and a day of labor. Normalize the scope before comparing the totals.
Replacement estimates are commonly provided at no charge, since the contractor is bidding on work. Diagnostic visits on a broken system are a different service and are typically billed. Ask which one you’re scheduling.
Equipment pricing moves, so most quotes carry an expiration, often 30 days. If a quote has no expiration date at all, ask what happens if material costs change between signing and installation.
Yes, across Front Range jurisdictions, and the contractor should pull it. A permitted job gets inspected, which is an independent check on the work that costs you nothing extra.
Get an Estimate You Can Actually Read
Every estimate we write itemizes equipment, scope, permit, commissioning, and warranty terms, so you can hold it up against anything else on your table and see exactly where the numbers come from. We handle heating and furnace installation and air conditioning installation throughout the Denver metro, from Arvada to Monument.
Request an estimate, and we’ll walk the document with you line by line.
