Start with a scope sheet
Create a column for each proposal. Record indoor and outdoor model numbers, controls, removal of existing equipment, electrical or duct work, permits when applicable, and cleanup. Mark an item “not stated” when it is absent; do not assume silence means inclusion.
Ask about design and startup
Ask what load assessment supports the chosen equipment and what installation checks you will receive. ENERGY STAR identifies equipment sizing and installation quality as important to the performance of a new system.
Reference: ENERGY STAR: HVAC Quality Installation. General guidance; equipment-specific advice requires an assessment.
Request documentation rather than accepting “same size as the old unit” as the entire explanation.Make the price comparable
Separate the base scope from optional upgrades. If one quote includes duct changes or additional electrical work, ask the other contractor whether that work is also needed and how it affects their total. Request an explanation of allowances, taxes, diagnostic charges, and change-order approval.
Read warranties as separate promises
Ask for the manufacturer’s terms and the contractor’s labor terms in writing. Note registration responsibilities, exclusions, and the process for requesting warranty service. Do not treat a headline warranty period as a description of every covered cost.
Questions to copy into your email
“Please identify everything included in the total, any expected extra costs, how the equipment was selected, and the results you will document at startup. Please also explain how changes to the approved work are priced and authorized.” This gives each contractor the same question to answer.
When the proposals still disagree
A second opinion can focus on the assumptions behind the disagreement. Ask whether it includes an independent equipment assessment or only a quote review. See replacement and second opinions and the HVAC cost factors guide before setting a project budget.