Most appliance and equipment warranties state when their coverage begins, and that line is easy to miss. Some count from the date of manufacture, some from the date of shipment, some from the purchase date on the sales receipt, some from delivery, and some from installation when a registration or installation record is filed. The paper should say which applies. If it does not, ask before you rely on it.
Find the start line first
Look for words such as effective, begins, starts, from the date of, or registration. Compare the start point against your install record. If coverage starts before the unit was put in service, part of the coverage period may run while the equipment is still in storage. If it starts later, there may be a gap at the front end.
Check the registration requirement
Some warranties ask you to register the product within a set window. Find out whether that window is measured from purchase, delivery, or installation, and whether you, the seller, or the installer is responsible for filing. Keep a copy of the registration confirmation with the warranty.
Read what the coverage includes
Separate the parts coverage from the labor coverage, because they often run for different lengths of time and under different conditions. Read the definitions near the front of the document, including what counts as wear, what counts as failure, and who counts as an authorized technician. The defined words control the meaning of every promise that follows.
Read the exclusions and the waiting period
Look for exclusions, such as damage from installation outside the stated requirements, water, power surges, or use outside the rated load. Look for a waiting period, which is a stretch of time after the start point during which certain claims are not paid. Read any pre-existing condition clause as well.
Ask about cancellation and transfer
Ask how the paper can be cancelled, whether any refund or credit is possible, and whether the coverage moves to a new owner if the home is sold. Transfer rules often require a written request and may carry a fee. Any amounts belong in the document itself, so read them there rather than rely on memory or a verbal summary.
Keep the file together
Store the warranty, the receipt, the registration confirmation, and the install record in one place. Note the start point in your log. When you plan a replacement, the start line tells you whether the paper is still active and whether it is worth reading the full terms again.
For the typical service life of the equipment itself, check the published tables on this site rather than the paper's own marketing language. The appliances ranked by typical service life page is a starting point for comparing any warranty length against the planning date of the system it covers.