Smart door locks — types, backup plans and what to check before buying

A smart door lock is one of the first things many people want and one of the easiest to get wrong. The door is the one place where a failed gadget locks you out of your own home, so the choice deserves more care than a light bulb. This guide covers the main types, the backup questions to ask, and how a lock fits with the rest of a smart home.

Two kinds of smart lock

• Retrofit units fit over the inside of your existing lock. They turn the thumb-turn for you, so the original lock, key and door stay as they are. They are easy to fit, can be removed, and suit rentals. The trade-off is that they only add convenience to the lock you already have; the outside of the door looks the same.
• Full replacement locks take the place of the whole lockset. They usually offer a keypad or fingerprint reader on the outside and a more integrated look. They involve drilling or modifying the door, and they depend on your door's thickness, lock body and hole layout matching the product.

If you rent, or the door and lock belong to someone else, a retrofit unit is the safer starting point. If you own the home and want to stop carrying keys altogether, a replacement lock may suit you better.

Ways to unlock

Most locks combine several methods. Each has its own weak spot:

1. PIN code: easy to share and revoke, but codes can be watched or guessed if they are simple.
2. Fingerprint: fast for daily use. Wet, dirty or worn fingers can fail to read, so it should never be the only way in.
3. Card or tag: handy for children and helpers. A lost card needs to be removable from the system.
4. Phone app or Bluetooth: convenient, but it depends on your phone's battery and the app working.
5. Mechanical key: the old-fashioned fallback. Check that the lock you choose still has one.

The backup questions

Before buying, find out the answers to these:

• What happens when the batteries run flat? Look for low-battery warnings well in advance, and a way to power the lock temporarily from outside, such as a contact point for a power bank.
• What if the electronics fail? A mechanical key override is the most reliable answer.
• What if the Wi-Fi or internet is down? The lock should still open with a PIN, fingerprint or key. Remote features may stop, but the door must not.
• How are codes managed? You should be able to add, remove and time-limit codes, ideally with a log of who opened the door and when.

Think about fire safety and building rules

A door is an escape route as well as an entry point. Make sure anyone inside can always open it quickly without a code, key or phone. If you are replacing a main door lock, also check the rules of your building, estate or condominium management and your insurer, as some places have requirements for what may be changed. When in doubt, ask them before you buy.

Where a lock fits in the rest of the home

A lock becomes more useful when it works with other devices. Common ideas:

• Switch on the hallway light when the door is unlocked in the evening.
• Turn off lights and aircon when the last person leaves and the door locks.
• Send a notification when a child's code is used after school.
• Remind you if the door was left unlocked at night.

These automations should add convenience, not make decisions that could lock someone out. Keep the lock's own operation independent of the rest of the system, and treat automation as a bonus.

Common questions

What happens when the lock batteries run flat?

Look for low-battery warnings well in advance, and a way to power the lock temporarily from outside, such as a contact point for a power bank. A mechanical key override is the most reliable backup.

Should I choose a retrofit lock or a full replacement?

A retrofit unit fits over the inside of your existing lock, can be removed and suits rentals. A full replacement takes the place of the whole lockset, needs drilling or modifying the door, and depends on your door matching the product.

Will the lock still open if the Wi-Fi is down?

It should. The lock must still open with a PIN, fingerprint or key. Remote features may stop, but the door must not. See our door lock and security setup.

What to check before you start

• Door material, thickness and the existing lock type
• Whether you own the door, or need permission
• Who needs access: family, helper, guests, short-term visitors
• Where the lock gets its power, and how you will know the battery is low
• Whether you want it to work with an existing smart home platform

Choosing a lock for your door? Tell us about your door and who needs access and we will suggest what is likely to suit.