Do Smart Locks Work Without Power?

Yes, and it is one of the few questions in this category with a completely clean answer. A smart deadbolt has no mains cable, no transformer and no low-voltage wiring. It runs on batteries sitting inside the door. So when the street loses power, the lock does not notice: the keypad still lights, the fingerprint reader still reads, the key still turns, and the bolt still throws.

Yale says this in its own words on the Assure Lock 2 product page: the lock is battery powered, so you keep access during a power outage. That is the opposite of the situation with security cameras, where a power cut takes the router with it and a cloud-only camera stops saving anything — a problem we worked through in do security cameras work without power?

So the useful version of this page is not about the grid. It is about the two failures that actually happen: the batteries going flat, and the network going down while the power stays on. They need completely different answers.

What stops during a power cut, and what does not

Nothing on the lock stops. Everything that depends on your router does, because your router is plugged into the wall.

That means the local half of the lock — keypad codes, fingerprint, the physical key, and Bluetooth from a phone standing at the door — is unaffected. The remote half is gone for the duration: you cannot check the lock from work, cannot let a neighbour in while you are away, and cannot ask Alexa or Google anything, because those commands travel out through the maker’s service and back. August states its assistant integrations and remote access as requiring Wi-Fi, which is the same fact from the other direction.

There is one real consequence of that worth planning for: a power cut is exactly when you might want to let somebody in remotely, and it is exactly when you cannot. If that scenario matters — an elderly relative’s door, a holiday let changing over — the fix is a keypad code they already have, not a cleverer lock. Alarm systems take the problem more seriously than locks do: Ring publishes an up-to-24-hour backup battery in its Alarm base station, and SimpliSafe publishes network backup plus up to 24 hours of battery on its base station, with cellular backup and professional monitoring requiring a subscription.

The failure that actually happens: flat batteries

Smart locks do not fail because of the grid. They fail because somebody ignored a low-battery warning for six weeks. The good news is that every maker we cover warns you, and every one of them publishes a way in afterwards — but they are three different ways, and which one you are comfortable with is a buying decision, not a settings decision.

Route one: the physical key.Yale is explicit about it: if the batteries die, you can always dig out the back-up key, which is included. Schlage includes one physical key with the Encode Plus and publishes the 5-pin tumbler C keyway it fits. This is the simplest and most reliable escape there is, with one honest caveat — a keyway is also a thing that can be picked, which is why key-free locks exist at all. The full argument is in are smart locks safe?

Route two: a USB jump.Wyze publishes the neatest answer in the category: if the batteries die while you are away, the USB-C port allows an instant, brief charge for you to enter your home. A power bank in your bag or your car is then the key, which is genuinely convenient — and genuinely dependent on you having a power bank.

Route three: your existing key, because the lock never touched it.A retrofit lock like the August attaches on the inside of the door over the deadbolt you already have, and August’s own product page says it that way: “so you can still use your keys”. If the lock’s batteries die, the original cylinder on the outside of the door has not changed at all. For renters this is usually the deciding feature anyway, and it is covered in can you still use a key with a smart lock?

What each lock publishes about losing power

Read the fifth row on its own. That row is the entire practical content of this page: three different escapes, all published, all perfectly workable — and you have to pick one when you buy, because you cannot retrofit a keyway onto a key-free lock.

Four things worth doing, none of which involve buying anything

Keep the backup key somewhere that is not inside the house. A key in the hall drawer solves nothing. A neighbour, a car, a small outdoor lockbox: any of those works, and the choice is a security judgement about your own street.

Set a code for someone else, now, not later. The remote features are the ones that fail, and a code does not depend on anything. Yale publishes unlimited shared codes; Schlage publishes up to 100 scheduled codes.

Act on the first low-battery warning, not the fifth. Buy the cells when you buy the lock. On a Wi-Fi lock, expect the figures in how long do smart lock batteries last? to be the optimistic end, because the radio is the drain.

If you want remote access during an outage, back up the router, not the lock. A small UPS under the modem and the router keeps the whole chain alive for a typical short cut, and the lock was never the problem. That is the same fix the camera version of this question needs.

Three locks with a published way in

One per escape route, from our main lock ranking. The reason each is here is the table above, not a test we did not run.

The related questions

Whether the lock relocks itself after you walk through, and the one setting that makes that safe, is in do smart locks lock automatically? Whether any of this costs money every month is answered flatly in do smart locks require a subscription? And the bigger question — whether a smart lock earns its price at all — is in are smart locks worth it?