A contractor hands you a proposal for a $10,000 HVAC replacement. It's one page. Maybe two. It has a total at the bottom and a signature line. And somewhere in the middle, a list of items you've never seen before — model numbers, acronyms, labor codes, and scope language written for someone who does this for a living.
Most HVAC proposals are not designed to be understood by homeowners. That's not always malicious — contractors write what makes sense to them — but the result is that you're being asked to commit to a major purchase without a clear picture of what you're actually buying.
This guide decodes every section of a standard HVAC proposal, line by line. By the end you'll know what belongs there, what each item means, what red flags look like, and exactly what questions to ask before you sign anything.
The information asymmetry in an HVAC sale is significant. A contractor has installed hundreds of systems. You've replaced yours once, maybe twice in your life. They know exactly what the equipment costs wholesale, what the labor takes, and where the margin is. You're working from a single page of text.
A vague proposal isn't just confusing — it's a mechanism for cost overruns, equipment substitution, and scope disputes. When a proposal doesn't specify the equipment model number, a contractor can install something cheaper than what they quoted. When a proposal doesn't list the permit, you may get billed for it separately after the job. When the scope language is loose, disagreements about what was "included" are nearly impossible to resolve.
A well-written HVAC proposal is essentially a mini-contract. Before you sign it, it should tell you:
Before you read a single line item, look at the top of the proposal. This section should establish who is doing the work and what job they're proposing for. It sounds basic, but what's missing here is often telling.
Should be a legal business name, not just a person's first name and a phone number. Look it up — verify the business exists and matches what you found in your research.
Every legitimate HVAC contractor must be licensed in your state. The license number should appear on the proposal. Verify it's active at your state's contractor licensing board — most have a free online lookup. If it's missing, ask for it before proceeding.
General liability and workers' compensation. Some proposals note this; if it's not mentioned, ask for a certificate of insurance before work begins. An uninsured contractor working on your home is your liability.
Obvious but important — make sure the proposal is for your address and your system, not a copied template from another job with the wrong details still in it.
Pricing is valid for a defined window, typically 30 days. Equipment and material costs fluctuate — a proposal without a date or expiration offers no price protection.
This is the most important section of any HVAC proposal, and the one most frequently written in contractor shorthand. Every piece of equipment being installed should be listed individually with enough specificity that you can look it up yourself.
Example: Carrier 24ACC636A003 — 3-ton, 16 SEER2. The model number is non-negotiable. Without it, you cannot verify what you're getting, look up the warranty, or confirm the equipment matches what was installed. "3-ton Carrier unit" is not sufficient.
Once you have the model number, search it on the manufacturer's website. You'll see the full spec sheet, the warranty terms, and the efficiency rating. If the model in the proposal doesn't match those specs, something is wrong.
For a split system, this is either the air handler (with electric heat strip or no supplemental heat) or the furnace (gas or oil). The model number matters here too — and because the indoor and outdoor units must be matched and compatible. The proposal should specify both.
If the proposal mentions keeping your existing furnace or air handler, the contractor should confirm in writing that the existing unit is compatible with the new equipment and note any efficiency or warranty implications.
The evaporator coil sits above the furnace and is the indoor heat-exchange component for cooling. It must be matched to the outdoor unit in both size (tonnage) and refrigerant compatibility. This is frequently a separate line item from the furnace or air handler.
If no evaporator coil is listed and you're replacing the outdoor unit, ask why. Replacing only the outdoor unit without replacing or confirming the coil is a common source of problems and warranty complications.
What thermostat is included, if any? A basic programmable thermostat is standard; a smart thermostat (Ecobee, Nest, Carrier Cor) is usually an upgrade. Clarify upfront rather than discovering the cheapest thermostat on the market was installed without asking.
Don't want to look up every model number yourself?
Upload your proposal — we check every piece of equipment against the full market and flag mismatches. Free.Beyond the equipment itself, a legitimate proposal describes the installation work in enough detail to hold the contractor accountable for what they do — and don't do. These line items are where many proposals go vague, and where the most costly surprises tend to emerge.
Should be explicitly included. Who removes the old system? Who hauls it away? Some contractors charge extra for this or leave equipment on-site. Confirm it's in scope.
Modern systems use R-410A or the newer R-454B. The proposal should specify which refrigerant is used and confirm the initial charge is included in the price. Some contractors list refrigerant separately — confirm it's not a post-installation surprise.
If your old system used R-22 (Freon), old refrigerant must be legally recovered, not vented. The proposal should confirm proper R-22 recovery.
The outdoor unit requires a dedicated electrical disconnect box within sight of the unit. On many replacements, the old disconnect is incompatible with the new unit and must be replaced. This should be specified — and included in the price, not billed as a day-of add-on.
If billed separately: typically $100–$350The concrete or composite pad the outdoor condenser sits on. If the existing pad is cracked, improperly sized, or deteriorated, it should be replaced. The proposal should note whether the pad is being reused or replaced.
Replacement: typically $75–$200The line that carries moisture condensed by the evaporator coil to a drain. Should be inspected, and replaced or extended as needed. A missing or clogged condensate line is one of the most common causes of water damage from HVAC systems.
The copper refrigerant lines connecting the indoor and outdoor units. Usually reused if in good condition and sized correctly for the new equipment. The proposal should state whether the line set is being reused, inspected, or replaced — and under what conditions replacement would be triggered.
Undersized line sets reduce efficiency and can damage the compressor over time. Ask the contractor to confirm the existing line set is appropriately sized for the new system before installation.
Replacement: typically $200–$600+ depending on run lengthAn HVAC replacement requires a permit in the vast majority of U.S. jurisdictions. The permit triggers an inspection by a local building official — the check that confirms the work was done correctly and legally. The proposal should explicitly state whether the permit is included and who is responsible for pulling it.
Any contractor who says "we don't need a permit for this" should be pressed. An unpermitted installation can create problems when you sell the home, file an insurance claim, or have a warranty dispute.
If billed separately: typically $150–$500 depending on jurisdictionNot always included in a standard replacement, but worth asking about — especially in older homes. Leaky ductwork can reduce system efficiency by 20–30%, meaning a brand-new high-efficiency system still delivers disappointing results. Ask whether the contractor inspects ductwork as part of the installation, and what they'll do if they find problems.
Duct sealing, if added: typically $400–$1,200The most important thing to look for in an HVAC proposal isn't always what's there — it's what's not. Here's what commonly goes missing, and the typical cost when it shows up as a surprise after the job starts.
On paper, this looks like a $7,400 proposal. But with the missing permit, refrigerant charge, and disconnect — all standard on a legitimate installation — the real cost is likely $7,900–$8,150. The low number may look competitive until you add what's been left out.
Not sure what your proposal is missing?
Upload it — we check every proposal for missing scope items and flag them with cost estimates. Free.The bottom of most proposals contains the terms of the agreement and warranty language. This section is easy to skim past when you're focused on the price. Don't. This is what determines what happens when something goes wrong.
Major manufacturers offer parts warranties of 5–10 years on new equipment — but these warranties often require registration within a specific window (typically 60–90 days of installation) to unlock the full term. An unregistered system may only receive the base warranty (typically 5 years instead of 10). The proposal should specify the warranty term and who is responsible for registration.
For a matched system, many brands offer an extended warranty only if all components — outdoor unit, indoor air handler, and evaporator coil — are from the same manufacturer's compatible product line. Mixing brands or reusing an old component from a different manufacturer can reduce or void the equipment warranty.
This is the contractor's guarantee on their own work — separate from the manufacturer's parts warranty. Standard labor warranties run 1–2 years. A contractor offering 5 years on labor is confident in their work and worth noting. A contractor who offers no labor warranty, or buries a 90-day limit in fine print, is a flag worth flagging.
Standard payment terms for a same-day residential install are typically a deposit (10–30%) at signing and the balance on completion. Be wary of proposals requiring full payment upfront — that's unusual and leaves you with no leverage if problems arise.
Look for change order language. A well-written proposal specifies what triggers additional charges and requires your written approval before the contractor proceeds with anything outside original scope. Verbal change orders are a common source of billing disputes.
After reading the full proposal, run through these questions with every contractor before committing. They cut to what matters most.
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