@wickedflow I'd say it's quite good. The bowl has a smaller volume so it doesn't need as much to operate effectively as some of my other session portables. I can fill it with a single pinch of some fluffy ground herb. I know that's not an accurate measurement.. but it doesn't need much!
It's quite possible to fully extract a bowl without stirring or filling the bowl, you can just barely cover the screen or top it up, so I feel it uses battery power effectively. If you have some better quality 18650 than the stock one you can get quite a few sessions out of it.
I recorded my sessions last weekend, little different than my previous recordings...
Cold start powered by LG HG2; 3 min @ 210 C, 100% -> 95%.
Second bowl, cleared/repacked Vivant still warm, 3 min @ 210 C, 95% -> 87%.
I let it cool down to room temp and new bowl, 3 min @ 210, 87% -> 76%.
Cleared repacked still warm, 3 min @ 210, 76% -> 67%.
Same bowl turned up, 3 min @ 220, 67% -> 52%.
So it seems you get diminishing returns as the battery discharges, which is normal, but I feel like I could definitely get at least 2-3 more bowls out of that same battery. I'll try going till full discharge next time! (that's what she said)
So I guess it's up to you whether that meets your needs! But for me that's plenty of sessions for a portable, it extracts fully what you put in, and it's easy for me to have an extra 18650 fully charged on standby. So when it comes to efficiency I'm very satisfied with the Alternate.