Used hybrids were expected to be difficult to sell, on the assumption that a looming battery replacement would frighten buyers. The market has behaved differently, for several connected reasons.
Fuel saving is inherited by the buyer
Unlike a cosmetic option, a hybrid drivetrain keeps delivering its benefit to whoever owns the car, so a second owner is buying an ongoing reduction in running cost.
That value rises and falls with fuel prices, which is why used hybrid demand strengthens noticeably during periods when gasoline is expensive.
Buyers who drive high annual mileage in urban conditions capture the most from it, and they bid accordingly at the used end of the market.
The drivetrain wears less than expected
The engine in a hybrid does not idle, starts under electric assistance and often operates in a narrow load range chosen by the control system.
Electric assist during acceleration reduces the load the engine sees at the moments that stress it most, and regenerative braking spares the friction brakes.
Many hybrids use a planetary gearset rather than a conventional automatic with clutches and bands, which removes a common source of expensive failure.
Battery replacement proved rarer than feared
Packs are managed to stay within a conservative charge window and are actively cooled, both of which extend cell life well beyond early expectations.
Extended warranty coverage on hybrid components, required in some states, meant the risk was carried by the manufacturer through a large part of the vehicle's life.
An aftermarket for reconditioned packs and individual module replacement also developed, which lowered the worst-case cost that used buyers were pricing in.
Supply constraints supported prices
Hybrids were a modest share of new sales for years, so the pool of used examples is small relative to demand from buyers who specifically want one.
Certain models became known as durable and economical, and that reputation concentrated demand further onto a limited number of nameplates.
Thin supply against steady demand is the ordinary recipe for firm used prices, and it applied here regardless of the technology involved.
Where the value does soften
Plug-in hybrids behave differently, because their larger batteries represent more replacement exposure and their benefit depends on an owner charging regularly.
Early or unusual hybrid systems with limited parts support depreciate faster, since a repair may require a specialist rather than any franchised dealer.
The general pattern holds where the system is common, well supported and simple enough that an independent shop can work on it, which describes most mainstream hybrids now.