When it’s time to replace your furnace or upgrade your HVAC system, you’ll probably collect at least two or three bids. At first glance, those quotes may look similar — but dig a little deeper, and you’ll often find big differences in what’s included (and what’s not).
The problem? Choosing a bid based on price alone can cost you more in the long run. Missing services, hidden fees, or vague details can turn a “cheap” quote into a costly headache.
In this guide, I’ll walk you through exactly what to look for when comparing HVAC bids, the common omissions that can drive up costs, and how to make an informed choice.
📘 Before you compare bids, it helps to understand the cost breakdown. See How Much Does a New Furnace Cost? for a detailed overview of equipment, labor, and extra fees.
Why HVAC Bids Vary So Much
Two contractors can quote the same type of system but come back with prices that are thousands of dollars apart. The differences usually come down to:
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Equipment quality and efficiency – High-efficiency units cost more upfront but can save more long-term.
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Installation scope – One contractor may include duct sealing, permits, and testing, while another leaves those to you.
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Labor rates – Rates vary by region, company size, and crew experience.
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Warranty and service coverage – A longer warranty or free maintenance period can be worth the extra investment.
The lowest bid isn’t always the best deal — you need to compare the details line by line.
What Should Be Included in a Complete HVAC Bid?
A thorough HVAC bid should leave you with zero guesswork. Here are the key categories to check.
1. Equipment Specifications
Look for the brand name, model number, capacity, and efficiency rating (AFUE for furnaces, SEER2 for ACs). Without these details, you can’t be sure you’re comparing apples to apples.
The ENERGY STAR guide to HVAC efficiency ratings explains how ratings impact energy use and lifetime costs.
2. Labor and Installation Costs
Labor can account for 30–50% of your total HVAC cost, so the bid should break down:
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Estimated labor hours
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Hourly rates or flat-rate labor fees
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Additional charges for difficult installs (e.g., attic access, tight crawlspaces)
The ACCA Quality Installation Guidelines outline best practices that ensure labor is done right — which also helps you avoid costly performance issues later.
3. Permits and Inspections
In most cities, HVAC replacements require a mechanical permit, and sometimes electrical or gas permits too.
Your bid should state:
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Which permits are needed
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Who is responsible for obtaining them
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Whether inspection costs are included
You can check local requirements or review the ICC Residential Mechanical Code for national standards.
4. Ductwork and Venting
Even the best furnace won’t perform well with leaky or undersized ductwork. Your bid should state whether:
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Existing ducts will be inspected
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Repairs or modifications are included
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Sealing or insulation is part of the scope
The ENERGY STAR Duct Sealing Guide highlights how fixing duct leaks can improve efficiency and comfort — and why it’s worth addressing during installation.
5. Warranties and Guarantees
Check for both manufacturer warranties (parts) and installer warranties (labor). Questions to ask:
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How long is the warranty?
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Does it cover labor, or parts only?
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Who handles warranty claims if something fails?
The Federal Trade Commission’s guide to warranty rights is a good resource for understanding what’s enforceable and what’s marketing fluff.
What’s Often Missing from Lower Bids
Low bids can be tempting, but they sometimes skip important line items. Watch for:
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Disposal of old equipment – If not included, you could be billed separately.
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Electrical or gas line upgrades – Necessary for code compliance in some cases.
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Thermostat installation – Some bids exclude this unless you supply the unit.
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Post-installation testing – Airflow balancing and combustion testing ensure the system runs efficiently.
These “extras” can add hundreds of dollars after the fact.
How to Compare Bids Side-by-Side
Here’s my go-to method for homeowners:
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Create a spreadsheet – Make columns for each contractor and rows for each major category (equipment, labor, permits, ductwork, warranties, extras).
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Mark each as Included / Not Included / Extra Cost – This will quickly reveal gaps in coverage.
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Assign Value to Inclusions – For example, a duct sealing job worth $600 in one bid might explain a higher price compared to a bare-bones quote.
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Look at Long-Term Value – A slightly higher bid with better equipment and a longer warranty could save thousands in repairs and energy costs.
Red Flags to Watch For
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No model numbers listed – You can’t verify efficiency or features.
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Vague scope descriptions – “Install furnace” isn’t enough detail.
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No mention of permits or inspections – Could mean corners will be cut.
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Reluctance to provide a written, itemized estimate – Always get it in writing.
Final Thoughts – Choosing the Best Bid
When comparing HVAC bids, don’t focus solely on the total at the bottom of the page. A “complete” bid should give you confidence that:
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The right equipment is specified and sized for your home.
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All necessary labor, permits, and testing are included.
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The installer stands behind their work with a solid warranty.
You’re not just buying a furnace — you’re buying the service, installation quality, and long-term reliability that comes with it.
If you want to understand how system type affects cost over time, read Cost of High-Efficiency vs. Standard Furnaces: What’s the Payback Time? next. It will help you factor efficiency into your bid comparisons.
Alex Lane
Your Home Comfort Advocate
