The definition is one sentence and the whole argument is inside the last three words. "Physical depreciation" has to be measured somehow, and the federal regulation that supplies the definition does not supply a method. What fills that gap is state law, and the states have not converged. Three approaches are used. The first is replacement cost less depreciation, which estimates what a new item would cost and reduces it for age and wear. The second is fair market value, which asks what the item would have sold for immediately before the loss. The third, usually called the broad evidence rule, directs the adjuster or the court to weigh every relevant piece of evidence, including both of the other two, along with income the property produced and its remaining useful life. The same loss can produce materially different numbers under each, so the applicable state's answer is not a technicality.
Whether labor can be depreciated is a live and genuinely divided question, and it decides a large part of many claims. A roof replacement is roughly half materials and half work. Shingles wear out; the act of nailing them down does not. Arkansas resolved this by statute, adding Arkansas Code section 23-88-106 in 2017, which defines "expense depreciation" to include "the cost of goods, materials, labor, and services necessary to replace, repair, or rebuild damaged property", permits a policy to allow it, and conditions that on the policy carrying notice in a form approved by the Insurance Commissioner and on the insurer providing "a written explanation as to how the expense depreciation was calculated." That is one state legislating one answer with a disclosure condition attached. Other states have reached the question through their courts rather than their legislatures and have not all reached the same place. Anyone who has been offered a depreciated settlement has a specific question to ask, which is what was depreciated and on what basis, and Arkansas is the example of a state that requires the answer in writing.
Where it applies is broader than most people assume, and it is often not a choice. On the federal flood policy, actual cash value settlement applies to personal property, appliances, carpets and carpet pads, detached garages, two-, three- and four-family dwellings, and a single-family dwelling that is not the policyholder's principal residence. On a homeowners policy, contents are frequently settled this way unless replacement cost on contents was separately purchased. On a renters policy it is one of the two available bases. On the basic dwelling form used for some rental property, it is the default. So a household can carry replacement cost on the structure and still be paid a depreciated amount for everything inside it.
It is what an insurer pays on a totaled vehicle, and that is where the number surprises people most. When a vehicle is declared a total loss, the settlement is built on what the vehicle was worth immediately before the loss, not on what the owner paid for it, not on what it would cost to buy a comparable one after taxes and fees, and emphatically not on what is still owed on the loan. Because a car depreciates quickly and a loan balance falls slowly, the two figures routinely diverge, and the difference is the borrower's. The product that exists to cover that difference has its own page, and so does the underlying condition of owing more than the collateral is worth.
The word "actual" is doing no work, and reading it as a promise is the trap. It is easy to hear actual cash value as the honest or true value, or as the cash a policyholder would need to be made whole. It is neither. It is a defined valuation method that produces a number below the cost of replacing what was lost, by design, and the gap widens with the age of the item. That is not a criticism of the method, which correctly reflects that the policyholder had a fifteen-year-old roof rather than a new one. It is a reason to know which basis a policy uses before a loss rather than after one.