What is a critical loads panel and what should go on it?

A critical loads panel is a small electrical subpanel that holds only the circuits you want alive during an outage. The battery feeds that panel. When the grid drops, those circuits stay energized and everything left on the main panel does not.

It is the hardware behind the decision covered in our whole-home versus essential backup explainer. That page is about which mode to choose. This one is about how the essential mode gets built, which circuits belong on it, and why the answer is shifting as more systems ship with managed circuits instead.

A licensed electrician does every part of the physical work described here. Nothing on this page is an instruction for doing any of it yourself.

Why a subpanel exists at all

A battery has two ceilings and a subpanel respects both.

The first is continuous power in kilowatts. A battery rated for a given continuous output cannot run simultaneous loads that exceed it, no matter how full it is. Among the models we track, single-unit continuous output runs from the Enphase IQ Battery 5P at 3.84 kW up to the Savant Power Storage 20 at 12.5 kW, with the FranklinWH aPower 2 at 10 kW and the Tesla Powerwall 3 at 11.5 kW in between. If your whole panel can call for 20 kW at once and your battery delivers 5 kW, something has to prevent the call. A subpanel prevents it physically, by making most of the house electrically absent during an outage.

The second is usable energy in kilowatt-hours, which sets how long, and it is covered in the sizing guide. The first-order question is what turns on at all.

The candidate list, with the figures we can cite

The useful way to build a load list is one circuit at a time with a published number attached. Below is a checklist of the usual candidates. Wattages appear only where a manufacturer publishes them or where our own guides have already done the arithmetic from a published figure. Where no manufacturer figure exists, we say so rather than fill the blank.

Refrigerator: yes, almost always first. Two numbers matter and they are not the same. GE publishes 313 W for its GFE26JYMFS French-door model and Samsung publishes 115 V at 3.5 A for its RF30BB6600QLAA, which are running-compressor figures. The average over a day is much lower, because the compressor cycles: a refrigerator with a 700 kWh per year EnergyGuide figure averages about 80 W across 8,760 hours. Size the panel's power against the running figure and the runtime against the average. Full working in our refrigerator backup guide.

Sump pump: yes, if you have a basement that floods. Zoeller publishes 9.7 A at 115 V for the M53 Mighty-Mate, roughly 1,116 W running. Liberty publishes 5.2 A at 115 V for its 1/3 HP 237 and 257, about 598 W. Superior publishes 4.1 A for the 92341. What none of them publish is a starting or locked-rotor figure, which is the specification you would actually want. That gap and what to do about it is the subject of our sump pump guide.

Well pump: yes, and treat it as the hard one. If your water comes from a well, losing the pump means losing water entirely, which changes the calculus from convenience to habitability. It is also a large motor with the same unpublished-startup problem as a sump pump. Covered separately in our well pump backup guide.

Medical equipment: put it on the list and take the numbers from the device maker. Published examples: Philips publishes 350 watts average power consumption for the EverFlo stationary oxygen concentrator, and the Platinum 10L owner's manual published by React Health lists 585 W typical at 120 VAC. On the CPAP side, ResMed's user guides publish 53 W typical and 104 W peak for the AirSense 10 and 56.1 W typical and 73.2 W peak for the AirSense 11. These are wattage facts for sizing arithmetic and nothing more; what equipment you need running and for how long is a question for your clinician and your equipment supplier, not for us. See medical equipment backup and CPAP backup.

Heating controls: yes, and read this carefully. The circuit that runs a gas furnace's blower and controls, or a boiler's circulator, is usually a modest load and it is the difference between heat and no heat in a winter outage. Resistive electric heat is the opposite case and belongs in the exclusion list below. Our winter outage heating guide works the difference.

Internet and networking: yes, and we have no wattage to give you. A router, modem, and ONT are small loads and consumer network gear is not spec-sheeted the way appliances are. We are not going to publish an invented figure. Read the label on your own power supplies and add them up, or plan the circuit and measure it. If your household works from home, the work from home outage kit covers what that set actually looks like.

Lighting and a few outlet circuits: yes, sparingly. A modern LED lighting circuit is a small load. It is also one where per-fixture figures are on the box rather than in a datasheet we can cite, so treat the lighting line in any proposal as an estimate rather than a specification.

Garage door opener: small, intermittent, and regularly forgotten. If the opener is not backed up, you can end up unable to get a car out.

What usually does not go on it

Three categories get excluded, and the reasons are different.

Heavy resistive loads. An electric water heater, an electric range, a clothes dryer, and resistive space heat draw large, steady kilowatts with no duty cycle to hide behind. A motor load averages down because it cycles; a resistance element does not. This is the category most likely to empty a battery in an hour and least likely to matter for a day or two.

Large HVAC. Window units are usually fine and central systems usually are not, and the published figures show why. LG rates its 8,000 BTU LW8016ER at 660 watts and its 12,000 BTU LW1216ER at 990 watts on 115 V. Goodman's GLXS3B specification sheet lists compressor locked rotor amps of 41.2 for the 1.5-ton and 148.0 for the 5-ton at 208/230 V single phase. At 240 V, 148 A is roughly 35.5 kVA for the starting instant. The one maker in our tracked set that publishes a comparable number is Tesla, whose Powerwall 3 datasheet lists a Load Start Capability of 185 LRA. That is the right column to compare against a condenser nameplate, and almost nobody publishes it. Full treatment in our air conditioning guide.

EV charging. A Level 2 charger is the single largest load in most modern houses and it has an obvious property the others lack: you can simply not charge the car during an outage. It is the first thing controllers are configured to shed.

How smart controllers change the question

The subpanel approach is a wired, permanent decision: a circuit is backed up or it is not. Several makers now publish an alternative, where circuits stay on the main service and get switched off automatically when the battery needs them off. Here is what each documents.

• FranklinWH Smart Circuits Module. An optional aGate component controlling up to three smart circuits. FranklinWH publishes the ratings as one 50 A maximum at 120 V, one 50 A maximum at 120 V, and one 80 A maximum at 240 V, with the two 120 V circuits mergeable into a single 50 A 240 V circuit. The backup behavior is the part that matters here: FranklinWH states that when the system is running from batteries, either during a grid outage or off grid, homeowners can set a state-of-charge threshold below which the smart circuits automatically turn off, and the circuits reconnect when solar, a generator, or the grid brings the batteries back above it. Its own example is a pool pump. Source: FranklinWH Smart Circuits Module datasheet.
• Panasonic EverVolt SmartBox. Panasonic describes it as smart circuits, transfer switch, and backup connection in one box, providing control of up to six loads. The published breakdown is four 50 A and two 80 A loads at 120 V, with 120 V branches combinable to 240 V. The datasheet's state-of-charge note reads: turn off less critical loads automatically and extend battery usage time. Source: Panasonic EverVolt Home Battery System datasheet, marked preliminary, rev 2023.
• Qcells Q.HOME HUB 200SX PRO. The datasheet lists smart load branches directly: two branches at a maximum smart load of 80 A at 120 V, four branches at a maximum of 50 A at 120 V, and the ability to combine 120 V branches to 240 V. Source: Qcells Q.HOME CORE datasheet, rev 08, May 2025.
• Generac PWRcell 2 Smart Disconnect Switch. Generac states the SDS supports both partial and whole home backup, and publishes a maximum backed-up load panel of 200 A alongside a maximum non-backed-up load panel of 100 A, which is the partial-backup architecture stated in numbers. Generac also documents a different lever: every PWRcell 2 system includes an ecobee smart thermostat, and Generac states the system automatically optimizes energy consumption during outages with smart thermostat setbacks. That is load management by turning the thermostat down rather than by opening a breaker. Source: Generac PWRcell 2 spec guide, Jul 2025.
• Savant Power Storage 20. The specification sheet lists a load management platform as included and shows two named system configurations, a partial home backup single-unit application using a sub panel plus Savant Power Modules, and a whole home backup stacked application. Savant does not publish per-circuit ampere ratings on this sheet the way FranklinWH, Panasonic, and Qcells do. Source: Savant Power Storage 20 specification sheet, 009-2477-00.
• Tesla. Tesla's approach in the Powerwall 3 datasheet is the panelboard rather than the smart circuit. Gateway 3 publishes an internal 200 A panelboard with 8 spaces and 16 circuit breakers, and Backup Gateway 2 publishes an optional internal 200 A panelboard with 6 spaces and 12 circuits. The datasheet's example system configurations include one labelled Partial Home Backup. What the datasheet does not publish is a per-circuit shed threshold of the sort FranklinWH and Panasonic describe. Source: Powerwall 3 datasheet.

Two honest readings of that list. The controllers are genuinely different from a subpanel: instead of one permanent decision, you get a rule that reacts to state of charge, which is strictly more useful during a long outage. And the published detail varies enormously between makers, from FranklinWH's exact ampere ratings and reconnect behavior down to a phrase like load management platform included. Ask for the per-circuit ratings and the shed logic in writing, because those two facts decide whether the feature does what the sales conversation implied.

Building the list

Four steps, and none of them require an electrician until the end.

Write the circuits down, not the appliances. Backup happens per circuit. A kitchen circuit carrying the refrigerator may also carry a countertop outlet you do not want energizing a toaster on battery power.

Attach a published watt figure to each one. Use the appliance's own label or datasheet. Where nobody publishes a number, mark it unknown rather than guessing, and treat unknowns as a reason for headroom rather than a reason for precision.

Sum the realistic simultaneous draw and compare it to the battery's continuous kW. Not the sum of every nameplate, because they do not all run at once, and not the average either, because the peak is what trips.

Then check the hours. Average draw times your target outage length, plus margin for conversion losses, against usable capacity. Run it through the calculator with your own numbers before an installer's proposal becomes the only version you have seen.

Two questions to put to any installer at the end. Is this design a physical subpanel or a controller, and what happens to a circuit that is not on the list. And what is the continuous kW rating of the exact configuration quoted, not of the brand. A proposal that answers both is a proposal you can check. One that says whole-home backup without either is a sentence, not a design.