Do smart locks work in cold weather, and which batteries should they use?

Two ratings on one lock, and the batteries sit behind the warmer one#

A keypad deadbolt is two assemblies bolted through the door. The outside half carries the keypad and the cylinder and lives in the weather. The inside half carries the motor, the electronics and the battery pack and lives in your hallway. Makers who publish a temperature range publish one for each half, and the two are not close. (What the lock does on your network is a separate question, covered in the smart locks guide.)

Schlage's specification sheet for the Encode family (BE489, BE499 and FE789) lists "Outside lock body (exterior mounted)" at -30°F to 150.8°F (-35°C to 66°C) and "Inside lock body (interior mounted)" at 14°F to 122°F (-10°C to 50°C). Yale's Assure Lock FAQ gives an outside range of -22°F to 140°F (-30°C to 60°C) and an inside range of 5°F to 158°F (-15°C to 70°C).

The battery is on the inside half in both cases. Schlage's battery care page says its smart lock batteries "are installed on the interior side of the lock", and the Encode quick start guide shows the four AA cells going into a holder in the inside assembly, under the battery cover. Yale's FAQ tells you to loosen the screw "at the top of the interior battery cover" to change the 4 AA batteries.

So the -30°F on the box describes the half with no batteries in it. The half that holds the cells is rated 44°F warmer on the Schlage and 27°F warmer on the Yale.

The table: lock ratings beside battery ratings#

These are the figures in each manufacturer's own documents, as of October 2026. A blank means the documents read for this page give no figure, not that the lock has no limit.

And the cells themselves, from Energizer's data sheets:

Put the two tables together and the system floor is whichever is warmer: the lock's inside rating or the cell's rating.

In every case where both numbers are published, the lock runs out of rating before the alkaline cell does. A lithium AA rated to -40°F changes the cell column and leaves the answer column where it was.

Why "use lithium for the cold" sounds right and is not#

The advice starts from a true fact about cells. Energizer rates its L91 lithium AA to -40°F and its E91 alkaline AA only to 0°F, a 40°F difference. The L91 data sheet also publishes a capacity curve against temperature: at a 25 mA draw it delivers roughly the same capacity at -40°C as at room temperature, and at 250 mA it still delivers roughly 1,600 mAh at -40°C against about 3,600 mAh near 21°C. If your batteries were on the outside of the door, lithium would be the obvious answer.

They are not. The cells sit on the warm side, in a housing rated to stop at 14°F or 5°F. A cell that works at -40°F, in a lock whose electronics are rated to 14°F, buys nothing you can rely on. What matters is how cold the inside face of your door gets, and on a door into a heated room that is nowhere near these floors.

The advice persists for a second reason: it is correct for other devices. A sensor in a freezer or a garage has its battery in the cold, which is why the sensors guide puts cell chemistry ahead of the sensor itself for those locations. A lock's battery lives indoors.

Do manufacturers really say never to use lithium?#

Battery and lock blogs say manufacturers forbid lithium. Each maker's own wording splits five ways.

Schlage says avoid it. Schlage's battery care page (its Australia and New Zealand edition) says smart locks "provide the best performance when alkaline batteries are used" and, in a callout, "Avoid using lithium or rechargeable batteries". The Encode specification sheet lists "4 AA included" and gives no chemistry.

Kwikset says avoid lithium ion and recommends alkaline. For the Home Connect 620: "we highly recommend alkaline batteries from a major brand. Do not use re-chargeable or lithium ion batteries." Halo gets the same alkaline recommendation. Lithium ion is a rechargeable chemistry; a disposable lithium AA such as the L91 is lithium-iron disulfide, which the Kwikset text does not name either way. Kwikset's explanation for preferring alkaline is about warnings, not damage: rechargeables "will not harm your smart lock", but "the lock software and app are optimized for alkaline batteries, which have a distinct discharge curve", and a flatter curve means "you might not receive correct low-battery warnings".

Yale names no chemistry in its Assure FAQ. It says to insert "4 new AA batteries" and that "extreme high and low temperatures may affect battery performance". Nothing in the FAQ forbids or recommends lithium.

August requires lithium on one model. The August Wi-Fi Smart Lock "requires two (2) 3V CR123 or CR123A Lithium batteries (Panasonic are recommended)". The AA-powered August models take "standard non-rechargeable alkaline batteries". Every August model carries the same caution: "We do not recommend using rechargeable batteries because of their limited capacity."

Level ships on lithium. The Level Lock Touch Edition comes with a CR2 battery that goes into the bolt, and its guide warns: "Do not charge CR2 lithium batteries."

So "never use lithium" is wrong as a general rule: two of the five brands run on lithium cells by design. What is right is narrower: Schlage says to avoid lithium in its AA locks, Kwikset says to avoid lithium ion and rechargeables, and both build their low-battery warnings around the way alkaline cells fade. Energizer's L91 discharge chart shows why that matters. The voltage stays almost flat for most of the cell's life and then drops close to vertically near 3,500 mAh. A lock that reads voltage to estimate charge gets very little notice from a cell like that, which matters more than temperature if an automation unlocks your door and you rely on the lock to warn you before it stops.

When cold really does stop a smart lock#

The inside of the door is cold too. A lock on a door between an unheated garage and the outside, a shed, a gate or a three-season porch has both halves in the weather. Yale says plainly that the Assure "is not built to handle gates or applications where the interior of the lock is exposed to outdoor conditions all day or night". The same logic applies to every lock in the table: on that door the inside half's 14°F, 5°F or 32°F is the rating that counts, and a lithium cell does not change it. A door from a heated house into an attached garage is the reverse case, with the inside half in the garage. If you have just moved into a house with a smart lock on that door, read its inside rating against how cold the garage gets.

August's range is narrow. August publishes one range for its locks rather than an outside and an inside figure, and says they "are not designed to be weatherproof, and are not intended for outdoor use", with an operating range of 32°F to 104°F. That is fine in a hallway and wrong for a cold mudroom or garage.

It is colder outside than the outside rating. Schlage's outside half stops at -30°F, Yale's at -22°F. Below that the keypad is out of specification, so keep a working key on you.

The door binds. Kwikset calls bolt and strike misalignment "by far the most common contributor" to battery drain, and Yale says resistance on the bolt "will force the motor to work harder than normal and reduce battery life". If a lock starts draining in winter, check that the bolt slides freely into the strike before blaming the cells.

What happens when the battery does run out#

What happens next differs by lock. Schlage's Encode guide says that when the low battery icon is solid, "the lock will not work without new batteries", so the key is your way in. Yale's FAQ says that at critical battery the Assure "does not operate"; the YRD216 and YRD226 open with the mechanical key, and the keyless YRD256 takes a 9 V battery touched to terminals on the front. Kwikset's Halo Select warns at 10%, and at "Critically Low Battery" turns off its Wi-Fi, so remote lock and unlock, auto-lock and auto-unlock may stop before the keypad does. None of this is cold-specific; the locks guide covers keyways and emergency power.

A dead battery and an internet outage look alike from outside the door: the app stops answering. In an outage, codes stored on the lock still work, as what still works without the internet explains, because local control does not need the cloud. A dead battery stops the keypad too. Run your setup through the internet outage audit and keep the key on you either way.

Where this page stops#

• The locks and documents named. Kwikset's and Level's own pages give no temperature range, so the table leaves them blank rather than quote a retailer.
• Operating ranges, not lifetimes. A rating says the device is specified to work at a temperature, not how many months a set of cells lasts there. Energizer publishes a capacity-against-temperature curve for the L91 but none for the E91, so this page makes no claim about alkaline capacity at a given temperature.
• Your model's own guide wins. Check the guide in your box, especially for Schlage's US wording. If the lock uses a proprietary pack instead of standard cells, ask whether you can still buy it in five years, the question vendor shutdowns teach.

If you are choosing a lock rather than feeding one, the buying checklist and the security tradeoffs in smart home security come before temperature. If a lock has gone quiet and the batteries are fine, start with a device that stops responding.