The most useful contractor interview produces details that can be written into a proposal. “Are you good at heat pumps?” is hard to compare. “How will you document the heating load, low-temperature capacity, backup configuration, and commissioning results?” gives you something concrete to evaluate.
Prepare your equipment model numbers, recent energy bills, a list of comfort problems, and known building changes. Tell each bidder the same facts so differences in scope are visible.
Ask how the system will be selected
Request the basis for the proposed capacity and the exact equipment combination. ENERGY STAR’s hiring guidance recommends a home evaluation, attention to insulation and windows, duct inspection, and written itemized proposals. The old system’s capacity is useful context, not sufficient evidence that the same size is correct today.
Ask these questions in plain language:
- What information about my house will you use for the load calculation?
- How will planned insulation, window, or duct work affect the design?
- What indoor and outdoor model numbers are included?
- For a heat pump, how will heating capacity and backup operation be checked at our local design conditions?
- What changes to ducts, electrical service, drainage, or venting are included?
The goal is an understandable explanation and a written design basis. A homeowner does not need to become the system designer to request that documentation.
Turn scope into a comparison table
| Topic | Question to put to every bidder | Written item to request |
|---|---|---|
| Credentials | Which licenses and insurance apply to this work here? | Identifiers you can verify with the issuing authority |
| Permits | Who obtains permits and arranges inspections? | Included fees and responsible party |
| Existing equipment | What is removed, recovered, or disposed of? | Removal and site-restoration scope |
| Hidden work | How are unexpected changes authorized? | Change-order process and pricing basis |
| Completion | What measurements will I receive? | Commissioning checklist and results |
| Support | Who handles warranty and comfort callbacks? | Contact, coverage, and response process |
License categories and permit rules vary by jurisdiction. Check the relevant local authority; a directory badge or a manufacturer’s dealer designation does not answer every licensing question.
Ask what “commissioned” means
An installation should have a defined completion process. Ask which tests are required by the equipment manufacturer and which results will be recorded for your system. For a duct project, the DOE checklist describes leakage and airflow verification, including post-work results. Use that as a conversation starter, not a claim that the same test package fits every installation.
Ask whether final controls, backup heat, drainage, and homeowner instruction are included. Who returns if an inspection identifies a correction? What paperwork will you receive before the final contractual payment? Make the agreed milestones clear in the contract rather than creating a new condition after work is finished.
Separate warranty promises from service promises
Ask for the actual equipment warranty and the installer’s labor or workmanship terms. Who registers the products, and how will you receive confirmation? Which charges can remain during a covered repair? Does a maintenance plan add coverage, or only discounts and scheduling priority?
If a proposal includes an incentive, ask the contractor to identify the live program, qualifying model combination, application responsibility, and installation deadline. A rebate estimate is not the same as a reduction in the contractual price. Do not let an obsolete federal-credit calculation hide the amount you must pay.
Compare the answers, not the sales pressure
A hypothetical $500 difference between bids has little meaning if one excludes a permit, drain modification, or required electrical work. Use the quote comparison tool to mark unknown items instead of silently treating them as zero.
Speak with references about jobs similar to yours: an older-house duct retrofit is a different project from an accessible like-for-like replacement. Ask how the company handled problems after installation, not just whether the equipment looked neat.
Before signing, read the schedule, payment milestones, cancellation terms, exclusions, and change-order language. Obtain local professional advice if a substantial contractual term is unclear. A strong contractor can explain the work and put the agreed scope in writing without making you rely on a verbal promise.