A critical loads panel is a separate subpanel that holds only the circuits you want powered during an outage, such as the fridge, Wi-Fi, lights, furnace blower and well pump. Your battery or generator feeds that panel, not the whole house. That lets a smaller system cover what matters and avoids overloads from big appliances.
Electrical work can be dangerous: follow the manual, fuse and size every cable correctly, and use a licensed electrician for anything connected to household wiring.
How a Critical Loads Panel Works
- The main panel still serves everything from the utility
- Selected circuits are moved to a new subpanel
- The backup system (battery gateway, inverter or transfer switch) sits between the main panel and the critical loads panel
- In an outage, the backup system disconnects from the grid and powers only the critical loads panel
Like any subpanel, its neutral and ground stay separate (no bond), and it’s fed by a properly sized breaker and conductors.
What to Put in a Critical Loads Panel
| Usually include | Sometimes include | Usually leave out |
|---|---|---|
| Refrigerator / freezer | Microwave | Electric range |
| Wi-Fi / network | Well pump | Electric dryer |
| Lighting circuits | Garage door | Central AC (unless sized for it) |
| Furnace blower / gas boiler controls | Sump pump | Electric water heater |
| Medical equipment | A few kitchen outlets | EV charger |
| Bedroom outlets (phones, CPAP) | Mini-split | Hot tub |
Typical choices. Size your list with the battery’s kW and kWh ratings and the startup surge of motors.
Critical Loads Panel vs Whole-Home Backup
| Critical loads panel | Whole-home backup | |
|---|---|---|
| Battery size needed | Smaller | Larger, or load management |
| Install work | Move circuits to a subpanel | Gateway at service entrance |
| Flexibility in an outage | Fixed circuit list | Use anything (watch limits) |
| Overload risk | Lower | Higher without load control |
Smart panels and load controllers blur the line. They allow whole-home backup while shedding big loads automatically.
How It’s Wired
The wiring has to follow NEC Articles 702 (optional standby), 705 (interconnected sources) and 706 (energy storage), along with the equipment’s listing. Expect a permit and inspection. It’s a job for a licensed electrician.
Planning Tips
- List circuits from your panel directory and test what each one actually feeds
- Measure loads with a clamp meter or energy monitor
- Leave spare spaces in the subpanel for future circuits
- Label clearly so everyone knows which outlets work in an outage
Worked Example: Building a Critical Loads List
Start with each circuit’s load. DOE’s method for appliance use is watts × hours per day ÷ 1,000 = kWh per day. Example list (check your own labels):
| Circuit | Running watts | Hours/ | kWh/ |
|---|---|---|---|
| Refrigerator | 150 average | 24 | 3.6 |
| Chest freezer | 80 average | 24 | 1.9 |
| Furnace blower | 500 | 8 | 4.0 |
| Wi-Fi and network | 30 | 24 | 0.7 |
| Lighting (LED, two circuits) | 150 | 6 | 0.9 |
| Bedroom outlets (phones, CPAP) | 100 | 8 | 0.8 |
| Well pump (240 V) | 1,000 | 1 | 1.0 |
| Total | 12.9 kWh/ |
At 12.9 kWh a day, one 13.5 kWh battery covers about one day without solar. Peak simultaneous load is about 2,000 W plus motor surges. Most single home batteries handle that. See how many batteries to power a house.
Sizing the Subpanel Feed
The feeder breaker and conductors to the critical loads panel must be sized for the panel’s rating and the backup source. In battery systems, the battery’s continuous output often sets a practical limit. For example, a battery rated 11.5 kW at 240 V can supply about 11,500 ÷ 240 = 48 A continuous. A 60 A feeder would be typical in that case, but the equipment’s installation manual sets the actual requirement. Learn the formula in watts to amps.
Step-by-Step: Planning a Critical Loads Panel
- Map your panel. Turn off each breaker and note what loses power.
- Measure loads. Use a clamp meter or whole-home energy monitor. See how to use a multimeter.
- Choose circuits that match the battery’s kW and kWh.
- Check motor starting for well pumps, sump pumps and any AC.
- Pick a subpanel with spare spaces for later.
- Hire a licensed electrician, pull a permit and schedule inspection.
- Label every outlet that stays on during an outage.
Shared Neutrals and Multiwire Circuits
Some homes have multiwire branch circuits, where two hot conductors share one neutral. When moving them to a critical loads panel, both hots and the shared neutral must move together, and NEC rules require a handle tie or a two-pole breaker so both hots disconnect at once. Your electrician will identify these during planning.
Critical Loads With a Generator vs a Battery
| Battery | Portable generator | |
|---|---|---|
| Switching | Automatic, through the gateway | Manual transfer switch or interlock |
| Runtime | Limited by kWh, extended by solar | Limited by fuel |
| Best list | Efficient essentials | Essentials plus some larger loads |
| Noise and fumes | None | Engine noise and exhaust |
See transfer switch vs interlock kit and generator vs battery backup.
Smart Panels and Load Control
Some systems replace a fixed critical loads panel with smart breakers or load controllers that turn off big loads during an outage. Generac includes PWRmanager load control with PWRcell 2, for example. This approach can give whole-home backup with a smaller battery, because the system sheds loads like the dryer or EV charger automatically.
Common Circuit Choices by Battery Size
| Battery energy | Typical critical loads |
|---|---|
| 5 to 10 kWh | Fridge, Wi-Fi, a few lights, phone charging |
| 13.5 to 15 kWh | Add furnace blower, well pump, microwave, bedroom outlets |
| 27 to 30 kWh | Add a mini-split or limited central AC use, more outlets |
Illustrative. Your loads decide. For battery options, see Powerwall 3 vs Enphase vs FranklinWH.
FAQ
Do I need a critical loads panel for a home battery?
Not always. Some systems back up the whole home. A critical loads panel lets a smaller battery cover essentials.
How many circuits can go in one?
It depends on the panel’s spaces and the backup system’s power rating. Commonly 8–16.
Can I add circuits later?
Yes, an electrician can move more circuits if there are spare spaces and the system can handle the load.
What is the difference between a critical loads panel and a subpanel?
A critical loads panel is a subpanel. What makes it “critical” is that it’s fed by the backup system, so its circuits stay on in an outage.
Can I put my central AC on a critical loads panel?
Only if the battery’s continuous power and surge rating can handle it, and it has enough kWh for the runtime you want. Many homes leave central AC off and back up a smaller mini-split instead.
How much does a critical loads panel cost?
Prices depend on the panel, the number of circuits moved and local labor. Ask installers to list it as a separate line on battery quotes.
Does a critical loads panel need its own ground rod?
Normally not. A subpanel is grounded through the equipment grounding conductor from the main panel, with neutral and ground kept separate. Your electrician follows NEC Article 250 and local rules.
Can I switch circuits between critical and non-critical later?
Yes, an electrician can move circuits later if the subpanel has spare spaces. That’s a good reason to choose a panel with extra room.
Sources: NFPA 70 (NEC) 2023 Articles 250, 702, 705 and 706; manufacturer installation guides; DOE, Estimating Appliance and Home Electronic Energy Use; NFPA 70 (NEC) 210.4 (multiwire branch circuits). Accessed Oct 2026.
Related: Tadeto Circuit Breaker Finder Review, EcoFlow Delta 3 Max for Home Backup
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