Runtime
Runtime and charging
A stated runtime is a number from a laboratory: a full cell, a new appliance, no load worth mentioning. It is still one of the more useful figures in these listings, because the comparison it supports is between two appliances measured the same way rather than between a claim and your bathroom.
What the figure means
Running time is measured with the appliance new, the cell full and the motor turning freely. Nothing in that description resembles a head of thick hair, so treat the number as a way to rank appliances rather than as a promise about how long yours will last on a Sunday.
It also says nothing about the load. An appliance pushed through dense hair draws more current than one skimming a two-day face, and the same figure covers both.
The figures quoted on this site range from three quarters of an hour on a single-blade appliance to several hours on a trimmer, and both are the sellers’ own numbers.
Charging and quick charging
Most of these listings describe a full charge in hours and some describe a short charge that yields one session. Where a listing states neither, this site states neither, because a charging time is not something anybody can infer from a runtime.
The one hard rule around charging has nothing to do with time. It happens away from the basin, with dry hands, on an appliance that is already dry, and no water rating anywhere on the box changes that.
How the number ages
A cell delivers less as it gets older, which is a property of cells and not a defect in any particular appliance. An appliance that runs a good deal shorter after a few years than it did new is behaving normally rather than failing.
That is worth knowing at the outset. Where the cell is sealed inside, the day it stops holding a charge is the day the appliance ends, and a stated runtime is the only clue you get in advance about how much room there is to lose.
Cordless and corded
One appliance quoted here runs from the cord and only from the cord, and one offers both. Both arrangements sidestep the runtime question entirely, and both put a mains cable in the room where you are working.
For a scalp, which is the longest session anything on this site is asked to cover, the difference between an appliance that stops halfway and one that cannot stop is worth more than most of the other specifications on the page.
Stated and not stated
Stated by the listing
- A running time in minutes or hours, on the listings that print one.
- Whether the appliance can run while plugged in.
- Whether the charging arrangement is a supply, a stand or a cable.
Not stated anywhere
- The load the figure was measured under, or the state of the appliance when it was measured.
- How the figure falls over the life of the cell.
- Whether the cell can be replaced at all, and by whom.
Where this goes wrong
Comparing across categories
A trimmer’s hours and a shaver’s minutes get read as the same measurement, when the two appliances are doing entirely different amounts of work per minute.
Compare runtimes within one group, where the appliances are at least being asked the same question.
Buying for the last session
The appliance is chosen on a figure it will deliver when new and never again, and it disappoints in its third year rather than its first.
Assume you will lose a good share of it over the years and choose with that headroom in mind.
Charging beside the basin
The one arrangement no rating on the box covers becomes a daily habit, on a surface that is wet most mornings.
Move the charger to a dry room and accept the walk as part of the arrangement.
Cautions
- StopCharging happens away from the sink and the shower, with dry hands, and never while the appliance is still wet. A water rating describes an appliance in use, not an appliance connected to mains power.
- StopBefore any third-party power supply, read the voltage and the plug printed on the appliance itself or on the supply that came with it, and match both. A barrel that fits is not a match, and 15V into an appliance expecting 5V is a dead appliance.
- StopA corded appliance is a mains-powered appliance. It does not go into the shower, into a filled basin, or under a running tap, whatever a listing says about rinsing anything else.
Where to look next
- Voltage and chargers
What goes into the appliance while it charges, and the number that decides whether it survives.
- Scalp
The longest single session on this site, and the place a runtime figure stops being trivia.
- Rotary Shavers
Where the one listing with a stated running time in its group sits.