How Many Cycles a Year Does a Home Battery Really Do? Measured on 28 Batteries in LA Homes

These are all 28 Enphase batteries in our monitoring fleet with at least 300 days of clean daily charge and discharge data in the past year, 21 of them with two or more years. A full-equivalent cycle is the battery’s usable capacity discharged once, whether in one evening or over several partial discharges: a 10 kWh battery that delivers 5 kWh a day does half a cycle a day.

The operating mode explains most of the spread. Batteries set to store surplus solar and use it in the evening (self-consumption) did a median 219 cycles; those set to discharge in the expensive hours (savings) 266. Batteries set to Full Backup sit charged and wait for an outage: a median about one cycle. Two of the 7 now set to Full Backup cycled 188–217 times in the past year, so their setting most likely changed recently — a reminder that a mode chosen after an outage can quietly stay.

The utility made less difference than often assumed. LADWP-area batteries did a median 187 cycles and SCE-area batteries 218, even though LADWP still credits exports at the retail rate. The same pattern shows in home energy flows: see how much solar a home actually uses. How the modes work: how a home battery works.

Even the batteries that work every day rarely empty completely. In December the median one did 0.47 of a cycle a day, with a deep discharge (80% of capacity or more) on 18% of days; in late summer, when evenings are hot and the panels leave a surplus to store, 0.72 in September, with deep discharges on about a third of days in July and August. A battery sized on a June day will not fill the same way in December; see the battery sizing calculator.

Of every 100 kWh that went into the batteries that cycle, about 80 came back out. That is below the 89% Enphase lists for a single round trip, and the difference is mostly not the round trip. Batteries that sat full for backup and barely discharged still drew a median 1.5 kWh a day per 10 kWh of capacity — energy the battery takes just to stay ready, about 540 kWh a year. A cycling battery pays some of that cost too: for a 10 kWh battery moving a typical 6 kWh a day, about half that standing draw would be enough to account for the whole gap between 89% and what we measured.

For a backup-only battery that standing draw is the whole energy cost of keeping it ready; for a battery that cycles daily it is the price of shifting solar into the evening. Datasheet efficiencies of other brands are compared in how a home battery works.

For almost every battery the calendar ends the warranty first. Under the strictest cap in Enphase’s US battery warranties, 2.8 MWh of energy per kWh of capacity, the median battery would need 14 years; only two of 28, both cycling more than 300 times a year, would reach it inside a 10-year term. The 4,000- and 6,000-cycle caps are further away still. What a warranty promises about capacity, and how other brands cap use, is in how long home batteries last.

The state’s Self-Generation Incentive Program asks storage it pays for to deliver at least 52 full discharges a year, SCE’s program page says. Six of 28 batteries in our fleet did fewer in the past year, five of them set to Full Backup. What the program requires: SGIP battery incentives.

A battery’s pace also changes. Among 21 batteries with two or more full years, the median difference between their busiest and quietest year was 40 cycles, and three batteries spent a whole year almost idle (under 20 cycles) before or after a year of 100 or more. Checking the mode in the monitoring app once a season is the simplest way to catch a battery that has gone to sleep.

Even working batteries do not take a home off the grid: the battery homes we measured went without buying power on a median 0.4% of days. See what share of a home’s electricity solar covers.