Critical load panels, explained: How to get more out of your home energy

The world has been talking a lot more about home energy storage in recent years. The latest EnergySage Intel Home Electrification Marketplace Report shows that 73% of homeowners are interested in storage, and about 38% of homeowners who are installing solar panels are adding a battery. With more homeowners investing in solar and storage for resilience and savings, it's no surprise the sector is booming.

But with all this momentum, one lesser-known piece of the puzzle is getting more attention: the critical load panel. It's not the flashiest part of a solar-plus-storage install, but understanding how it works—and what's replacing it—can help you get more out of your battery investment.

A critical load panel is a secondary electrical panel, separate from your main breaker box, that your battery is wired to feed during an outage. Think of it as a curated list of the appliances and circuits you actually need when the grid goes down: your refrigerator, some lights, a phone charger, medical equipment, maybe your internet router. Basically, all your critical devices (get it?).

The point here is that with a critical load panel, your battery won't be backing up your whole home—only the stuff that really matters, so you're not accidentally using your stored energy to feed appliances or phantom loads you don’t need.

The average U.S. home uses about 30 kilowatt-hours (kWh) of electricity per day, according to the U.S. Energy Information Administration. But most home batteries store somewhere between 10 and 20 kWh of usable capacity. The math doesn't quite add up if you're trying to run your whole home from a single battery.

And it's not just total energy that's the issue—it's peak demand. Certain appliances draw a lot of power the moment they turn on. A standard electric clothes dryer, for example, can draw 5 kilowatts (kW) or more, according to the DOE's appliance energy estimator. Run that for two hours, and you've already burned through roughly 10 kWh—potentially half or more of your battery—in a single laundry session.

There's also the question of output capacity. Every battery has a maximum continuous power output (measured in kW), and if a single appliance demands more power than the battery can deliver, you risk damaging the battery, the appliance, or your home's electrical system.

The critical load panel solves all three of these problems at once. By routing your battery to a dedicated subpanel that only serves pre-selected circuits, it:

• Stretches your stored energy further by avoiding power-hungry appliances you don't need during an outage

• Ensures your battery isn't asked to output more power than it's designed to handle

• Protects your appliances and battery from unintended electrical failures

It's a relatively simple piece of hardware, but it's often what stands between a well-functioning backup system and a frustrating one.

The short answer: maybe.

The longer answer: it’s complicated. Many batteries on the market today are "stackable," meaning you can connect multiple units to multiply your usable storage capacity. Install two or three batteries together, and you may have enough stored energy to cover an average day's worth of electricity use for most households, even without a critical load panel restricting which circuits get power.

But "enough for an average day" isn't the same as "enough for a multi-day outage during a heat wave or winter storm," which is often when outages happen. For true resilience over multiple days, you'd also need to size your solar energy system to recharge your batteries each day, accounting for potentially reduced sunlight. It's doable, but it takes careful planning and the right system design.

If you're curious about what it would actually take to go off-grid with solar and storage, our off-grid solar guide walks through real-world case studies and the tradeoffs involved.

For most homeowners, the more practical question isn't, "Can I back up my whole home?" but, "Which circuits matter most if the grid goes down?" A good installer can help you answer that and design a critical load panel that keeps the important devices running.

Here's where things get genuinely exciting. The traditional critical load panel works fine, but it has a significant limitation: decisions about which circuits to back up are made at installation and then locked in. If you forgot to put your home office on the critical load panel, too bad—you'll need an electrician to make changes.

Smart load panels are changing that entirely. Instead of fixed, pre-selected circuits, these devices give you real-time, app-controlled flexibility over which appliances and circuits receive power during an outage. They also add energy monitoring, load shifting, and integration with solar, batteries, and EV chargers, turning your electrical panel from a passive distribution box into an active energy management hub.

The two leading players in this space are SPAN and ABB ReliaHome (formerly Lumin). They take different approaches to the same problem.

SPAN Panel

The SPAN Panel replaces your entire existing electrical panel with a smart panel that gives you circuit-level control from your phone. During a power outage, you can decide in real time which rooms and appliances stay on, switch your priorities on the fly, and see exactly how long your battery will last based on your current load. SPAN can reportedly extend average battery backup duration by approximately 40% compared to a traditional critical load panel setup.

ABB ReliaHome (formerly Lumin)

In January 2025, Lumin was acquired by ABB, the global electrification and automation giant, and the Lumin Smart Panel was reintroduced as the ReliaHome™ Smart Panel.

Unlike SPAN, which replaces your main panel entirely, the ReliaHome system is a retrofit device that installs alongside your existing electrical panel and adds smart control to up to 12 selected circuits. It's generally a less expensive option, and it's universally compatible with any electrical panel. It integrates with battery systems from Tesla, Enphase, SolarEdge, EG4, and FranklinWH, and features local network backup so the app keeps working even if your internet goes down during an outage.

Which is right for you?

SPAN is a good fit for homeowners who want the most comprehensive solution and are doing a major electrical upgrade or new installation anyway. The ReliaHome system makes more sense if you want smart load management without the cost and disruption of replacing your entire electrical panel. Your installer can walk you through which is the better match for your setup.

If you're adding a home battery to a solar system, critical load panel decisions happen early in the installation process, and they're not easy to undo. Getting them right from the start means fewer headaches down the road and a backup system that actually performs when you need it most.

For most homeowners, the conversation starts with a simple question: What do you actually need to keep running during an outage? From there, a good installer can help you decide whether a traditional critical load panel fits your needs or whether a smart load panel or smart breakers are worth the additional investment. As home electrification picks up, with EV chargers, heat pumps, and more all competing for capacity, having intelligent control over your electrical system is becoming less of a luxury and more of a practical necessity. It's one of those things that's easy to overlook when you're focused on solar panel brands and financing options, but it can make a meaningful difference in how well your system actually serves you.