By Jeremy Koski · September 17, 2026
A smart home depends on continuous power. When the grid goes down, your smart locks, cameras, thermostat, and network gear all stop working. This guide walks through the backup power options that keep your smart home running during an outage, what each costs, and how to choose the right one for your setup.
A smart switch needs power to the switch, the hub, the router, and the modem. If any one of those links fails, the whole chain breaks. A two-hour outage can mean your cameras go offline, your locks stop responding to the app, and your thermostat loses its schedule. The most critical devices are the router, modem, network switch, and your automation hub. If those stay online, your automations keep running. If they go down, everything goes down.
The simplest and cheapest backup power option is an uninterruptible power supply (UPS). A UPS is a battery-backed power strip that switches to battery instantly when it detects a power loss. For smart home networking gear, a UPS is essential.
A small UPS rated at 600 to 900 VA (roughly 350 to 500 watts) can keep a modem, router, and Home Assistant server running for 30 to 60 minutes. Brands like APC and CyberPower make reliable units in the $80 to $150 range.
Modem, router, network switch, Home Assistant server or hub, and any Zigbee or Z-Wave coordinator. Do not put high-draw devices like space heaters or air conditioners on a UPS. They will drain the battery in minutes and may exceed the inverter capacity.
For help setting up Home Assistant on a UPS-backed server, see our guide on Home Assistant on Raspberry Pi in 2026.
A portable generator runs on gasoline or propane and can power essential circuits during a longer outage. A 5,000 to 7,500 watt unit can run a refrigerator, furnace blower, lights, and networking gear simultaneously. You connect it with a manual transfer switch or interlock kit on your electrical panel. They cost $500 to $1,500 depending on wattage. The downside is manual setup: you wheel it outside, start it, connect it to your panel, and switch over the load. They must be operated at least 20 feet from the house due to exhaust.
For smart home purposes, a portable generator is a good option if you already have one for general emergency use. Make sure your networking gear and Home Assistant server are on the circuits the generator covers.
A home standby generator is a permanently installed unit that runs on natural gas or propane. It connects to your electrical panel through an automatic transfer switch. When the grid power drops, the generator detects it, starts automatically, and switches your home over to generator power within 10 to 30 seconds. When grid power returns, it switches back and shuts itself down.
Standby generators range from 10,000 to 24,000 watts and cost between $3,000 and $8,000 installed. They are the most seamless option because they require no manual intervention. Your automations keep running with only a brief interruption while the generator starts. Installation requires a permit and a qualified electrician. If you want professional installation, book an on-site assessment and we can help evaluate your options.
Home battery systems like the Tesla Powerwall and Enphase IQ Battery store electricity and power your home during an outage without burning fuel. They are silent, require no maintenance, and install indoors. A Tesla Powerwall 3 stores 13.5 kWh and delivers up to 11.5 kW. An Enphase IQ Battery 10T stores 10.5 kWh. They switch over in milliseconds, so your networking gear and Home Assistant server may not even notice the transition. With solar panels, a daytime outage lets your array recharge the battery while it powers your home.
Tesla Powerwall is a DC-coupled system that integrates tightly with Tesla solar panels. Enphase IQ Battery is AC-coupled, which means it works with any existing solar installation regardless of panel brand. If you already have solar panels from a non-Tesla installer, Enphase is often the easier choice. Both systems can be expanded by adding additional battery units.
Battery systems cost between $8,000 and $15,000 installed, depending on capacity and whether you add solar. For more on solar and electrical integration, see our solar and electrical services page.
An automatic transfer switch (ATS) sits between your generator or battery system and your electrical panel. It monitors grid power and switches your home to backup power automatically when the grid fails. A whole-home ATS handles your entire panel. A sub-panel ATS covers only essential circuits, letting you use a smaller generator or battery. The ATS is usually included with a standby generator or battery system. For a custom setup, your electrician will select the right ATS for your load.
Sizing starts with listing the devices you want to keep running during an outage. Add up their wattage and multiply by the hours you want them to run. Here is a rough guide:
For a UPS, size it to 1.5 times the total wattage of connected devices. For a generator, add 20 percent headroom for surge loads. For a battery system, size the kWh capacity to cover the hours of backup you need.
Here is how the options compare:
Most smart home owners should start with a UPS for networking gear, then add a portable generator or battery system if outages are frequent. A standby generator is worth the investment if you live in an area with severe weather or unreliable grid power.
Home Assistant can monitor your backup power systems and trigger automations based on power state. If you have a UPS with network management, Home Assistant can detect when it switches to battery and trigger automations: turn off non-essential lights, switch thermostats to energy-saving mode, and send a notification to your phone.
For battery systems, the Tesla Powerwall and Enphase both offer local APIs that Home Assistant can poll. You can build dashboards showing battery charge, power flow, and estimated time remaining. If you want help integrating this, our IT services team can configure the integration and build the dashboards.
For most smart homes, a layered approach works best. Put a UPS on your modem, router, and Home Assistant server to handle short blips. Add a portable generator or battery system for outages lasting more than an hour. If you want fully automatic backup, install a home standby generator or battery system with an automatic transfer switch. Book an on-site visit and we will assess your power requirements and recommend the right system.
For more practical smart home guides, check out our post on running Home Assistant on a Raspberry Pi in 2026.