AC300: inverter efficiency threshold, no-load consumption

I read a few topics and external articles so I understand an inverter with no load connected still draws power.

Not complaining here, just getting to understand my device better to use it in a more predictable/educated way.

My questions are specific to AC300 as I only found topics about AC200.

Test conditions today: full sun, PV input reading on average 100-120Watts, no load, AC inverter on.

  • 11am, battery is at 50%
  • 2pm, battery is still at 50%

In 3hrs, that’s at least 300Wh generated.
B300 is 3072Wh, so ignoring all laws of physics, my unit generated about 10% of battery equivalent charge.

With AC200’s no-load inverter in mind (forum admin mentions 23Wh), the AC300’s no-load consumption seems higher. Is it correct that it drains about 2-3% of battery equivalent per hour, which is about 100Wh?

Also, the inverters’ 86% efficiency seems quite good. Considering the truck-vs-moped analogy where a simple burger needs to be delivered, I wonder: from what AC load is the AC300 inverters’ efficiency at its top?

Use case: fridge + other 24/7 appliances in a future offgrid configuration.

Ideally a few data points like « efficiency at 50W, 150W, 300W, 1000W, 3000W » would really help me.

Last question: does DC have the same « no load draw » ? I didn’t test the « DC out on with no load » yet.

Thanks in advance for the help!

When performing calculations, do not rely on the Display meter. It is an estimate only and not considered fully accurate.

It is all but impossible to directly measure the inverter power consumption with no load, but yes, assume that all else being fairly equal a 3000W inverter will use more standby power than a 2000W inverter.


Any idea where the sweet spot is to reach a decent inverter efficiency?
It’s more an order of “150W is too low, 600 is close to the max efficiency” than an accurate figure of course.

Some of this you’re probably not going to like, but it’s better to know so as best to deal with it. This unit is great for some things, terrible for others. The AC inverter is going to draw about 60w any time it’s powered on. The screen itself is going to take about another 15w. The 24v uses about 30w and the 12v on the B300 (if the AC300 is not powered) is about 15w. It stands to reason you don’t want any of these active if you’re not using them.

For raw power this thing is a beast. It will push 3000w until drained. It’s great for short duration heavy loads. It is horribly inefficient with small loads. If you keep something running with AC 24/7 you’ll lose over 1400watts a day just keeping the unit powered. You’ll have to do the math but clearly the faster the discharge, the more efficient. If you discharge it in an hour, and you can, you’d only be losing about 60watts. But that’s 60watts every hour so it becomes less efficient as time goes.

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It’s a large, hungry beast indeed.

Out of curiosity, how did you get such accurate figures? Did you use a clamp-shaped power meter?

I agree with the use case where it delivers a lot of energy for a short period. It’s absolutely flawless in that scenario. Wife and I are clearing brambles from a patch of land with 1200Watts power tools and a full afternoon is far from draining the B300. No inverter overload in spite of the heavy duty work. Congrats @BLUETTI .

I’ll add a second use case given that it’s the only portable unit to accept huge PV input (2x 1200W MPPTs). If you just intend to buy a few foldable panels then indeed the math you share will make the unit disappointing. That was my first impression on small panels. Bluetti informed someone in a different post that the charging threshold of large units like AC300 is 100 (120?) Watts.

My AC is now mostly connected to a 2,4kWp array of panels in my garden. The inverter is off during the night.

Summer: stops charging after 8pm and starts charging from 8am. It loses about 5% a night.

Inverter is on from 9am to 7pm and the internal consumption is not an issue as the panels generate so much that 60-100W of overhead is not noticeable. It powers an office (2-4p) and the excess energy is streamed to a washing machine, water boiler, kettle, etc.

It might not be a full replacement for a wall-based Victron device though. Even then, my Multiplus II 5000 still drain about 40-50W per unit when on idle (and 5W on full standby). Main advantages of Victron over Bluetti IMHO: automatic transfer switch and non-proprietary battery & connectors (eg. Pylontech).

I’d simply say that Bluetti isn’t lagging behind given the nature of their all-in-one solution.

Let’s just avoid an AC300 if it’s to be plugged to a couple 120-200W foldable panels.
Buy it if you can often connect to larger arrays.


It’s good to know you’re making it work for you. I got those figures from a youtube video that was rather in depth and I trust it. For my end was more crude. I just tried to confirm what was in the video with a couple simple tests. I had the AC on with no load for 10 hours and noted the expected 20% drop. Did the same with the B300 charged and unplugged from the AC300. Lost 5%. Continued the test on the B300 for a full day and the drop maintained at that rate.

I’m upgrading my house-bound installation (Victron) so the Bluetti system will be repurposed before winter.
I guess it’ll store excess solar power from the inverters (if any during winter), and will reconnect with PV arrays as I setup the pannels in my other piece of land (no grid).
Suppose the experience will put the AC300 to a new level of testing :slight_smile:

Regarding your experience, I’ll be glad to confirm / test the results myself. I should soon obtain a clamp-shaped amp meter. Will be easy to monitor energy in & out between AC300 and B300 given its wire is so exposed compared to AC200Max & the likes.

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