How long do home batteries last, and do they degrade like an EV?

Every lithium battery loses a little capacity in two ways. Calendar aging is the slow loss that happens just from getting older, even if the battery is never used. Cycle aging is the loss that comes from charging and discharging. NREL models both, and which one dominates depends on how the battery is used.

A home battery that cycles roughly once a day is mostly limited by cycle aging. One that sits with little use is mostly limited by calendar aging. In both cases the loss is gradual and predictable, not a sudden cliff. A battery does not stop working at some fixed age, it simply holds a little less than it did when new.

The most important factor is chemistry. Most electric vehicles, e-bikes, phones, and power tools use nickel-manganese-cobalt cells, usually written as NMC. NMC packs a lot of energy into a small, light package, which is ideal for moving a vehicle, but it degrades faster when it is stressed. That is why EV guidance often suggests keeping the charge between about 20% and 80%.

Home storage batteries, including the EG4 PowerPro units Potrero installs, use lithium iron phosphate, written as LFP or LiFePO4. LFP is heavier per unit of energy, but it is far more durable and tolerates full daily cycling much better than NMC. It is the same chemistry difference that makes home batteries more thermally stable, which is covered in our article on battery safety.

The practical takeaway: the 20% to 80% rule you may have heard for an EV does not apply the same way to an LFP home battery. These batteries are designed to use most of their capacity every single day.

The EG4 PowerPro batteries Potrero installs are rated for roughly 8,000 cycles at 80% depth of discharge. At about one full cycle per day, which is typical for a home battery, that works out to somewhere on the order of two decades of daily use.

It helps to read a cycle rating correctly. It is a reference point, not the end of the battery life. A battery does not stop when it reaches its rated cycle count. It keeps storing and delivering power, just a bit less than when it was new, and the decline stays gradual.

The system estimates state of charge from the battery voltage, so Potrero runs a calibration sequence about once a year that maps voltage to state of charge. A useful byproduct of that calibration is a direct reading of the energy the battery actually delivers over a full cycle.

That gives a real, measured value for storage capacity each year, which can be compared against the expected aging curve. Instead of trusting a spec sheet for two decades, you get evidence of how your specific battery is holding up, and anything falling faster than expected can be caught early.

Using the battery in grid programs, where it exports stored energy at high-value times, does add some wear. But because LFP is durable and those programs pay real money, often a few hundred dollars a year, capturing that value is usually the economically sound choice even after accounting for the extra cycling.

EV charging is a large load, and the smartest way to handle it protects the battery. The optimal approach routes excess solar, the power that would otherwise be exported, straight to the car rather than storing it in the home battery first. That avoids the roughly 10% round-trip loss of charging and then re-discharging the battery, and it spares the battery an extra cycle.

Longevity claims are easy to make and hard to verify, so it is worth asking pointed questions. The answers also tell you whether the installer understands the difference between an EV battery and a home storage battery.

Potrero sizes and operates the battery to deliver value across its full life, while tracking the degradation trend so anything abnormal is caught early. Because LFP tolerates daily use, the design assumes the battery works hard every day rather than sitting in reserve to avoid wear.

There is a real cost to being overly cautious. A battery that is never cycled to preserve its capacity is also never delivering savings or backup. The better goal is to put the battery to work, measure how it ages, and plan around the gradual, well-understood decline of LFP rather than the faster fade of EV-style chemistry.