Energy storage for residential solar systems used to mean one thing—a bank of lead-acid batteries that kept the lights on for people who either by choice or by necessity lived off the grid. The batteries needed tending, required a roomy storage space, and struggled to provide enough power for appliances like electric ranges.
The falling price of lithium batteries, a media blitz by Tesla that popularized its Powerwall battery, and the growing sophistication of the solar industry has changed all of that. Solar panels paired with batteries—what the industry calls “solar + storage”—is gaining ground with utility-scale solar projects as well as residential-sized systems. Justin Baca, the Solar Energy Industry Association’s vice president of markets and research, estimates that by 2026, 30% of residential solar installations will be paired with battery storage, up from 13% in 2021.
Batteries and related equipment push up the cost of a residential system by tens of thousands of dollars, but the benefits can be persuasive. Batteries do more than provide electricity when the grid is down. In areas where utilities have time-of-use rates, homeowners can save money by storing energy when rates are low and using the power at times of the day when grid electricity is more expensive. Where net-metering reimbursements are low, batteries allow homeowners to use more of the electricity they produce rather than sell it at a reduced price.
A range of systems
Solar + storage systems vary in cost, complexity, and versatility. Batteries can be added when the solar system is installed originally, or added later. At its most basic, a system consists of solar panels, an inverter that turns the direct current produced by the panels into alternating current used by household appliances, a single battery, and systems controls.
When solar panels are producing electricity, power flows first into the…
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