Introduction: The Smart Lock Upgrade Dilemma
When it comes to securing your smart home, August has long been the gold standard for retrofit smart locks. The company pioneered the concept of a smart lock that installs over your existing deadbolt, preserving your exterior hardware while bringing your entryway into the modern era. For years, the August Smart Lock Pro (3rd Generation) was the undisputed champion of the lineup, beloved by smart home enthusiasts for its robust feature set and versatile connectivity. However, the release of the August Wi-Fi Smart Lock (4th Generation) introduced a compelling new promise: built-in Wi-Fi, eliminating the need for a separate bridge.
But does removing the bridge truly make for a better smart lock? As with any major hardware revision, the shift from the 3rd Gen Pro to the 4th Gen Wi-Fi involves significant trade-offs. In this comprehensive upgrade test, we put the flagship 4th Generation against its legendary predecessor to determine if the newer model is a worthy successor, or if the older Pro model still holds the crown for specific user profiles. According to extensive testing by Wirecutter, both locks remain top contenders in the market, but their underlying architectures serve very different smart home philosophies.
Design and Physical Footprint: A Much-Needed Diet
The most immediately noticeable difference between the two generations is the physical footprint. The 3rd Gen Pro is a sizable piece of hardware. Measuring 3.4 inches in diameter and protruding about 2.2 inches from the door, it can sometimes interfere with storm doors or tight entryways. Its bulk is a direct result of the internal Z-Wave radio, the Bluetooth antenna, and the battery housing required to power them.
August addressed this aggressively in the 4th Gen Wi-Fi. By utilizing a more modern, miniaturized internal circuit board and switching battery types, the 4th Gen is roughly 45% smaller by volume. It measures just 2.83 inches in diameter and sits closer to the door. Aesthetically, the 4th Gen features a sleeker, more modern matte finish with a subtle indicator ring, whereas the 3rd Gen Pro has a more utilitarian, industrial look with a prominent faceplate. If you have a narrow door frame or a glass-paneled door where clearance is an issue, the 4th Gen Wi-Fi is the undisputed winner in terms of physical design and installation flexibility.
Connectivity: Built-In Wi-Fi vs. The Z-Wave Bridge Era
The defining feature of the 4th Gen is right in its name: Wi-Fi. August integrated a 2.4GHz Wi-Fi radio directly into the lock, meaning it connects straight to your home router without requiring the August Connect Wi-Fi Bridge. Out of the box, this makes the 4th Gen significantly easier for the average consumer to set up. You simply plug in the lock, connect it to your app, and you have remote access.
The 3rd Gen Pro, on the other hand, relies on Bluetooth for direct phone communication and requires either the August Connect bridge or a compatible Z-Wave hub (like SmartThings or Hubitat) for remote access and cloud integrations. While this sounds like an inconvenience, it is actually a massive advantage for advanced smart home users. Z-Wave is a low-power, mesh-networking protocol designed specifically for smart home reliability. When connected to a local Z-Wave hub, the 3rd Gen Pro operates with near-zero latency and does not depend on August's cloud servers. If your internet goes down, your Z-Wave hub can still control the lock locally. The 4th Gen's reliance on Wi-Fi means that heavy network congestion or a dropped router signal can result in the lock showing as 'offline' in your app, a frustration frequently noted in CNET's long-term review of the device.
Battery Life: The Achilles Heel of the 4th Generation
If there is one area where the upgrade test reveals a glaring regression, it is battery life. The 3rd Gen Pro runs on four standard AA batteries (alkaline or lithium). Because Z-Wave and Bluetooth Low Energy (BLE) are incredibly power-efficient protocols, a good set of lithium AAs can easily power the 3rd Gen Pro for 12 to 18 months, depending on usage.
The 4th Gen Wi-Fi ditches AAs in favor of two CR2 lithium batteries. While CR2 batteries are excellent for high-drain devices like cameras, the constant power draw of maintaining a Wi-Fi connection is brutal on the lock's power reserves. Users of the 4th Gen frequently report needing to swap batteries every 3 to 6 months. Furthermore, CR2 batteries are more expensive and harder to find in a pinch than standard AAs. If battery longevity and low maintenance are your top priorities, the 3rd Gen Pro remains vastly superior.
Smart Home Ecosystem and Hub Compatibility
Ecosystem compatibility is where the divide between these two locks becomes a chasm. The 3rd Gen Pro is a multi-protocol powerhouse. It features Z-Wave Plus, Bluetooth, and HomeKit support baked in. This makes it natively compatible with Apple HomeKit, Samsung SmartThings, Hubitat, and Ring Alarm via Z-Wave. For users building a local, privacy-focused smart home on Hubitat or Home Assistant, the 3rd Gen Pro is a dream device.
The 4th Gen Wi-Fi relies on cloud-to-cloud integrations for platforms like SmartThings and Alexa. While it does support Apple HomeKit (added via a firmware update after a controversial launch without it), it lacks the local Z-Wave radio. As the industry moves toward the unified Matter standard, both locks currently rely on August's proprietary bridge or cloud integrations to interface with Matter controllers, though August has promised future firmware updates to improve interoperability. For now, if you use a local hub like Hubitat, the 3rd Gen Pro is the only logical choice.
Security, Auto-Unlock, and DoorSense
Both locks utilize August's proprietary DoorSense technology, a small magnet mounted on the door frame that tells the app whether the door is physically closed or ajar, preventing the lock from deadbolting into an open door. Calibration is identical across both generations.
Auto-Unlock, which uses geofencing to detect when you leave and Bluetooth RSSI (Received Signal Strength Indicator) to unlock the door as you approach, is slightly faster on the 4th Gen. The newer Bluetooth chip in the 4th Gen wakes up and authenticates your smartphone a fraction of a second faster than the 3rd Gen. However, both locks are incredibly reliable in this regard, and the real-world difference in auto-unlock latency is measured in milliseconds, making it a negligible factor in the upgrade decision.
Head-to-Head Specification Table
| Feature | August Smart Lock Pro (3rd Gen) | August Wi-Fi Smart Lock (4th Gen) |
|---|---|---|
| Connectivity | Bluetooth, Z-Wave Plus, Wi-Fi (via Bridge) | Bluetooth, Built-in 2.4GHz Wi-Fi |
| Dimensions | 3.4 x 3.4 x 2.2 inches | 2.83 x 2.83 x 1.81 inches |
| Power Source | 4x AA Batteries | 2x CR2 Lithium Batteries |
| Avg. Battery Life | 12 - 18 Months | 3 - 6 Months |
| Smart Home Protocols | Z-Wave, HomeKit, Cloud APIs | Cloud APIs, HomeKit (via firmware) |
| DoorSense Included | Yes | Yes |
Performance and Battery Benchmark
The chart below illustrates the stark contrast in battery longevity between the two generations based on daily usage profiles. The 3rd Gen Pro's Z-Wave efficiency vastly outperforms the 4th Gen's Wi-Fi power draw.
The Verdict: Is the Upgrade Worth It?
Deciding between the August Smart Lock Pro (3rd Gen) and the August Wi-Fi Smart Lock (4th Gen) ultimately comes down to your smart home setup and your tolerance for battery maintenance.
Stick with (or buy) the 3rd Gen Pro if: You are a smart home enthusiast using a local hub like Hubitat, SmartThings, or Home Assistant. The Z-Wave Plus radio provides local, lightning-fast control that doesn't rely on cloud servers. Furthermore, if you hate the idea of buying expensive CR2 batteries every few months, the 3rd Gen's AA battery life is vastly superior. It remains the workhorse of the August lineup for power users.
Upgrade to the 4th Gen Wi-Fi if: You are a casual smart home user who relies primarily on the native August app, Alexa, or Google Home, and you want a cleaner setup without plugging a Wi-Fi bridge into a wall outlet. The 4th Gen is also the clear choice if you have a tight door clearance where the bulky 3rd Gen simply will not fit. Its smaller, sleeker design is a major physical upgrade, provided you can stomach the increased battery maintenance.
In the end, the 'flagship' 4th Gen traded raw protocol versatility and battery endurance for mainstream convenience and a smaller chassis. Choose the one that aligns with your home's ecosystem, and you won't be disappointed.
