I installed a 10 kWh lithium battery beside my inverter last spring, mainly to stop buying expensive evening electricity. My rooftop solar system already covered most daytime use, but before storage I was exporting power at a low rate and importing it back after dinner. The battery changed that pattern immediately.

I set it to charge from solar during the afternoon and discharge from 4 p.m. until 10 p.m., when my utility’s time-of-use rate is highest. On clear days, the battery usually reaches 100% before dinner and runs the refrigerator, router, lights, and heat-pump overnight. By breakfast, it is often around 25%, so the panels have plenty of room to refill it.

My monthly bill fell from roughly $180 to $70, although weather and appliance use make the exact savings vary. In the summer, I save about $3 to $4 each evening by avoiding grid power during peak hours. I like seeing that result in the utility app: solar production fills the battery, then the battery carries the house when the sun is gone. It has made our energy use feel less wasteful, especially because I used to watch surplus midday electricity disappear onto the grid.

The only scare came during a week of cloudy weather, when the battery stopped discharging at 18% state of charge. The monitoring app showed a temperature warning, and I found that a storage-room vent had been blocked by a cardboard box. After moving it, I restarted the battery inverter and watched the temperature return to normal over an hour. I did not open the pack or bypass any safety settings; the manual clearly says to call support for electrical faults.

Anyone considering a diy lithium ion battery pack for solar should budget for proper ventilation, monitoring, and professional electrical checks before switching it on.