Critical load panels: What you need to know

You may have noticed an increase in coverage of energy storage in the news lately, especially here on our blog. Energy storage continues to increase in popularity throughout the country (according to Wood Mackenzie and the ESA, residential storage had its best quarter ever to start 2020), and with good reason: batteries provide myriad benefits, form backup power and peace of mind, to further financial savings.

As energy storage is installed in more homes around the country, one lesser-known but vital aspect of the installation is also increasing in importance: the critical load panel. In this article, we’ll cover what they are, why they’re necessary, and some cool new tech to keep an eye on that may revolutionize how you think about your electrical panel.

The critical load panel is a piece of hardware that functions as a second electrical panel; it is a critical (get it?) component of an energy storage installation. Instead of directly feeding your battery into your existing electrical panel or circuit breaker, a battery will typically be designed to feed into a critical load panel to ensure that you’re backing up all of your essential appliances and circuits and not accidentally using your stored energy to feed any appliances or phantom loads you don’t need.

Critical load panels allow you to appropriately size a battery for your home’s needs to maximize the energy you store. Across the country, most homes use an average of over 30 kilowatt-hours (kWh) per day, whereas most solar batteries store 17 kWh or less. As a result, if you try to backup your entire home with a single battery, you’ll likely run out of stored energy in less than 24 hours, partially defeating the purpose of installing a battery.

What’s more, certain appliances require more electricity than others, meaning if you turn them on, you risk draining your battery very quickly. For instance, according to the DOE’s handy energy usage calculator, a clothes dryer may have a load of 3 kilowatts (kW) or more! If you have an LG Chem RESU 10H (one of the most popular batteries on the market) and run your 5 kW dryer for two hours, you’ll have already depleted all of the energy you stored.

And finally, in some instances, your appliance may actually require more electricity to operate than your energy storage system can output, meaning you run the risk of damaging the battery, your appliance, and your home’s electrical system if you forget (or don’t realize) that you’re running on backup power and try to run the appliance from the battery.

As a result, energy storage systems are designed with a critical load panel to protect your appliances and battery from unintended electrical failures while ensuring that your most important appliances and devices remain on and blissfully connected.

The short answer: maybe!

The longer answer: it’s complicated – many batteries currently available in the market today are “stackable,” meaning you can install multiple batteries together to double (or triple) your storage capacity. Stacking multiple batteries may be more than enough to cover your home’s electrical needs for an average day.

However, this quickly leads to a second question: can I go off-grid with solar plus storage? In this instance, you need to not just size a solar and storage system to power your home for a single, average day, but for multiple days in a row, perhaps even when you’re using greater than average amounts of electricity per day. To learn more about the feasibility of going off-grid with solar & storage, check out our two-part series on the subject, complete with case studies: part 1 and part 2.

If you want to install storage but also want more control over which particular appliances and circuits are backed up, you’re in luck: multiple startups are now creating “smart load panels” that provide much greater flexibility when adding an energy storage system. The two primary players in this space–Span.io and Lumin–provide similar flexibility and control through different methods. Span replaces your existing electrical panel with their smart panel, while Lumin is a separate piece of hardware that sits next to your electrical panel.

In each case, the technology allows you to access, monitor and control individual circuits with your phone or computer. In practice, this means you can decide in real-time which appliances or parts of your house you want to power with your battery and which aren’t essential at that moment.

If you’re interested in joining the rush toward solar plus storage, we can help! By registering for an account on EnergySage, and indicating your interest in storage when you sign up, you’ll receive solar + storage quotes from up to seven local installers. And the best part? We provide the service at no cost to you. Sign up today to see how much you can save with EnergySage.