Start with the number on the quote and you will miss most of what the plan costs. The total over the life of a service contract is set by the clauses around the sticker. This piece walks through the clauses that move the total, so you can see where the money comes from before you sign.
Read the term and the renewal path
Find the length of the term first. The term sets how much of the system's remaining life the contract covers. Then find out whether the rate is fixed for the term or can change at renewal. Some contracts reset the rate when they renew, and that reset is where long-run cost tends to rise. Check who sends the renewal notice, how far ahead it arrives, and what happens if you do nothing.
Find the charges that come on top
Many plans add a charge each time a technician visits. Find that line and ask three things. Does it apply to every visit, or only to visits that end in a covered repair? Does it apply when the technician finds nothing to fix? Is it waived in any case? Write the answers next to the clause.
Look for add-ons as well. An extra covered item, a second system on the same plan, or a rider that adds a named appliance each carries its own cost, term, and cancellation rule. Treat each add-on as a separate decision.
Check what the plan leaves to you
Exclusions move cost back to the owner. Read the list of what is not covered and mark the parts that wear out in the middle of the system's life. Check whether labor is covered, and if it is capped, find where the cap is written. A plan that looks complete on the front page often has its gaps on the exclusion page.
Ask whether age sets the terms
Some contracts use the age of the equipment at signing to set the rate, the term, or the coverage list. An older system can enroll under different terms than a newer one. Ask the seller whether the install year you give changes anything in the contract. If it does, the offer you see depends on that year, so confirm the year on the install record before you go further.
Set the contract against the system's planning window
The contract is one side of the math. The other side is how long the system is likely to run. Our published service life tables give that planning window for each system, and the appliances ranked by typical service life page is the place to start. If the contract term ends well before the system's typical service life, the renewal path will carry more of the long-run cost than the first term does. For the published figures on each system, use the tables on this site rather than any figure a seller quotes.