Backup runtime way shorter than expected, what am I missing as a beginner?

[TioPlato]

I’m new to home battery backup and I’m a little nervous because my system works, but the runtime is way shorter than I expected. The battery percentage drops faster than I thought it would, even when I feel like I am only running a few basic things. I’m trying to understand if this is normal and I just misunderstood the math, or if I’m getting hit by something like inverter losses, surge loads, or some kind of idle draw I did not account for.

A specific moment that made me ask was this week during a short outage when everything switched over smoothly and it felt satisfying because the setup actually did its job. Then I looked at the battery after a bit and it had dropped more than I expected, and I started second guessing my whole plan. For people who have been doing this longer, what are the most common beginner misunderstandings that cause shorter runtime, and what is the simplest way to figure out what is eating the most power?

 

[Alan]

The easiest way to stop guessing is to look at real time power draw on the app or inverter display and watch it as you turn things off one at a time. Most people discover one or two big hitters, fridge cycling, furnace fan, space heater, well pump, or a dehumidifier, and everything suddenly makes sense.

 

[VictorGen]

The simplest way I’ve seen people figure it out is to look at the live power draw during backup and start turning off circuits one at a time to see what makes the number drop. It’s boring but it works, and it quickly reveals the surprise culprits like dehumidifiers, space heaters, or a freezer you forgot was on the backup panel.