Created: June 10, 2026
Local-First Smart Home
Architecture
Core host
A dedicated Home Assistant Green gateway is the brain of the system. Running on purpose-built hardware (rather than a general-purpose single-board computer) keeps the automation logic insulated from the storage-wear and reliability problems that plague DIY setups, and gives me a stable baseline to build on.
Two local radio meshes
Device traffic rides on two independent local meshes, both terminated on the Green, so almost nothing routes over Wi-Fi or the internet:
- Z-Wave, via the Home Assistant Connect ZWA-2 coordinator, carries the smart deadbolt, the thermostat, and a metered plug.
- Zigbee, via the Home Assistant Connect ZBT-2 coordinator, carries Third Reality smart plugs.
The mains-powered plugs pull double duty as mesh building blocks: the Z-Wave metered plug repeats the Z-Wave mesh and the Zigbee plugs repeat the Zigbee mesh, so each network is self-healing and grows more robust with every device I add. Running two protocols on a single host does introduce RF and placement trade-offs, so to give each radio clear, interference-free spacing I 3D-printed custom wall-mount brackets for the Green and both antennas.
Why two protocols
Running both Z-Wave and Zigbee is deliberate. Their strengths are complementary, so each one carries the devices it suits best: Z-Wave for the must-never-fail hardware, Zigbee for breadth and quick wins.
| Z-Wave | Zigbee | |
|---|---|---|
| Radio band | Sub-GHz (~908 MHz in the US), clear of Wi-Fi | 2.4 GHz, shared with Wi-Fi and Bluetooth |
| Range and reach | Strong wall penetration per hop, but a route is capped at about four hops | Shorter individual hops, but many of them; large meshes blanket more area |
| Interference | Quiet, uncrowded spectrum | Has to be planned around Wi-Fi congestion (channel and placement) |
| Ecosystem | Certified for tight interoperability; fewer devices, higher prices | Huge, inexpensive, near-ubiquitous device selection |
| Power and bandwidth | Very low power, low bandwidth | Low power, a bit more bandwidth |
| I use it for | Rock-solid essentials: the deadbolt, thermostat, and metered plug | Breadth and quick wins: smart plugs today, sensors next |
In short, Z-Wave gives me dependable, interference-resistant control for the things that absolutely have to work, while Zigbee's cheap, plentiful devices make it easy to expand coverage and add sensors as the system grows. Together they also mean no single radio is a single point of failure.
Integrating with the existing Google and Arlo ecosystems
Home Assistant layers on top of what the house already runs rather than ripping it out:
- Google Home. The property is covered by a Google Nest mesh Wi-Fi network with Google and Nest speakers in nearly every room. Home Assistant coordinates with that ecosystem today, and a near-term goal is migrating automations (such as multi-room Spotify playback) off Google Home and onto local HA control.
- Arlo cameras and doorbells. Motion and doorbell-press events flow into Home Assistant for snapshot push notifications.
Topology
The Home Assistant Green sits at the center, with each radio coordinator anchoring its own self-healing mesh. The existing Google and Arlo ecosystems and a handful of optional cloud services connect in, but the local core keeps working if any of them go away. New devices simply join the nearest mesh, hopping through the mains-powered plugs that act as repeaters.
Hardware Bill of Materials
Prices are rough estimates for new equipment. This covers the gear that makes up the local-first core; pre-existing pieces I integrated rather than bought for this project (Arlo cameras and doorbells, Google Nest speakers and mesh Wi-Fi, and the propane provider's tank monitor) are listed in the notes below.
| Category | Item | Qty | Est. Unit | Est. Total | Notes |
|---|---|---|---|---|---|
| Gateway | Home Assistant Green | 1 | $99 | $99 | Dedicated local controller; the brain of the system |
| Radio coordinator | Home Assistant Connect ZWA-2 | 1 | $69 | $69 | Z-Wave 800-series; carries the lock, thermostat, and mini plug |
| Radio coordinator | Home Assistant Connect ZBT-2 | 1 | $35 | $35 | Zigbee / Thread; carries the smart plugs |
| Climate | Honeywell T6 Pro Z-Wave thermostat | 1 | $130 | $130 | Drives the dual-fuel heat pump + propane furnace logic |
| Security | Kwikset Home Connect 620 Z-Wave smart lock | 1 | $180 | $180 | Per-person PIN codes; presence auto-lock |
| Smart plug | Third Reality Zigbee smart plug (3RSP02028BZ) | 4 | $12 | $48 | Energy-metered; mains repeaters for the Zigbee mesh |
| Smart plug | Z-Wave mini plug with power meter | 1 | $30 | $30 | Energy-metered; repeater for the Z-Wave mesh |
| Weather | Ambient Weather station | 1 | $180 | $180 | Backyard PWS; current conditions for the climate and weather subsystems |
| Power | CyberPower CP850PFCLCD UPS | 1 | $140 | $140 | PFC pure sine wave; bridges to the generator; shared with the home network |
| TOTAL | ~$911 | Excludes taxes, pre-existing gear, and the 3D-printed mounts |
Notes
- The mains-powered plugs double as mesh repeaters, so each one also strengthens its network.
- Wall-mount brackets for the Green and both antennas were 3D-printed in-house for clear, interference-free spacing.
- Pre-existing and integrated (not bought for this project): Arlo cameras and video doorbells, Google Nest speakers and mesh Wi-Fi, and the propane provider's tank monitor.
- Ongoing cost (not a one-time purchase, so it sits outside the totals above): a Home Assistant Cloud (Nabu Casa) subscription, about $65/year, which powers remote access and also helps fund Home Assistant's development.