The case for batteries

Home battery systems have two primary roles: peak-shaving and back-up power during outages.

Peak shaving is the everyday process of storing excess energy from the solar PV for later use. During normal operation it is used in the home to offset the higher electrical rate periods such as “on-peak” and can be a substantial savings on your utility bill. As utility rates continue to increase in cost, the savings realized by peak shaving become even more beneficial.

Home back-up power is a contingency that, although not used daily, can be extremely important. During a power outage, homeowners with traditional grid-tied solar systems will be without power alongside those with no solar at all. This can be a concern during a prolonged period. The battery may be used to power essential loads such as your refrigerator, medical equipment, lights, and microwave for cooking. You can also keep your internet and tv powered for news and updates. Since the solar PV will now continue to operate, the battery continues to recharge during the day and be used by the home during a prolonged outage.

So why the concern over power outages? It is felt that the U.S. electrical system is becoming less dependable, and the problem is likely to get worse before it gets better.

Large, sustained outages have occurred with increasing frequency in the U.S. over the past two decades, according to a Wall Street Journal review of federal data. In 2000, there were fewer than two dozen major disruptions, the data shows. In 2020, the number surpassed 180.

Utility customers on average experienced just over eight hours of power interruptions in 2020, more than double the amount in 2013, when the government began tracking outage lengths. The data doesn’t include 2021, but those numbers are certain to follow the trend after a freak freeze in Texas, a major hurricane in New Orleans, wildfires in California and a heat wave in the Pacific Northwest left millions in the dark for days.

The U.S. power system is faltering just as millions of Americans are becoming more dependent on it—not just to light their homes, but increasingly to work remotely, charge their phones and cars, and cook their food. One big factor is age. Much of the transmission system, which carries high-voltage electricity over long distances, was constructed just after World War II, with some lines built well before that. The distribution system, the network of smaller wires that takes electricity to homes and businesses, is also decades old, and accounts for the majority of outages.