Before you accept a proposal, check the people behind it. Ask for credentials, proof of insurance, and a written scope, and verify each one against its source. This site does not rank or recommend any company, so the steps below apply to any contractor you consider.
Ask for the license and check it yourself
Ask for the license number and the license type that applies to the work. Look it up with the state or local licensing board using the number, not a copy the company hands you. Confirm that the name on the license matches the business named on the proposal.
Ask for proof of insurance
Ask for a certificate of liability insurance, and for workers compensation proof if the business has staff. Ask the insurer to confirm that the coverage is active. Note the policy period so you can request a fresh copy if the work runs long.
Ask for the scope in writing
A written scope lists the equipment model, the removal work, who holds the permit responsibility, the start and finish conditions, and any items left out. Review each proposal against this list, line by line, before you compare the totals.
Ask who holds each warranty
Equipment warranties and labor warranties often come from different parties. Ask which party backs the parts, which party backs the labor, and how a claim reaches each of them. Get the answer in writing, and keep it with the install record.
Check references and the callback record
Ask for references from similar installs, and ask whether the business returns for service calls. Ask how callbacks are handled and who pays for the return visit when the cause is the original work. Write the answers down so you can compare them with the scope.
Use the service life guides on this site to set your planning window, then judge each proposal against that window.