Battery service or new laptop? The per-year arithmetic
A battery is the one repair that arrives on a schedule. Capacity falls steadily, then the machine starts shutting down under load, and suddenly a laptop that was fine last month cannot finish a meeting.
The decision looks emotional and is actually arithmetic: a battery service is worth doing when the expected years of use it buys cost less per year than replacing the machine.
The arithmetic
A battery service restores runtime, not performance. So the question is how many more years the machine will be usable after the service, and what else is likely to fail in that window.
Cost per extra year = battery service price / years of use gained.
Compare that with the annual cost of the replacement you would otherwise buy: (new price - end value) / years you would keep it. If the service is cheaper per year, service the battery. If it is not, the battery is a signal that the machine is at the end of its economic life, even if it still works.
The number people forget
The old machine keeps losing value while you decide. A machine worth 650 today and 380 in six months is losing about 45 a month while you wait, which dwarfs most battery decisions. That is the same decay the waiting calculator prices, and it means delay is rarely the cheap option here.
When a battery service is clearly right
- The machine is under three years old and otherwise healthy.
- A replacement of the same class costs several times the service.
- The service is done by someone who also checks the charging circuit, not just the cell.
When it is not
- Two or more other components are already marginal: hinge, fan, screen coating, storage.
- The machine cannot run the current operating system, so the extra year is a year of an unsupported machine.
- The service costs more than a third of the machine's current resale value. At that ratio you are repairing an asset you could sell, and the arithmetic rarely works.
How to decide in five minutes
Look up the service price. Estimate the extra years honestly, in whole years, not optimistically. Divide. Compare against the per-year cost of the replacement you would actually buy. If the two numbers are within twenty percent of each other, decide on how much you like the machine, because the money is a tie and pretending otherwise wastes an afternoon.
The calculator on this site does the same division with your numbers, including the resale value you give up by keeping the machine.