Current at output when grid charging?

I"m confused…

I connected my Bluetti to my furnace today with a simple changeover/transfer switch similar to this video below.

Per this video (since the Bluetti has a floating ground) I connected all of the neutral/whites in the new switch and no longer have a floating ground (and neutral connected to the house system). I also have a simple 3rd party energy meter on the bluetti where the furnace plug connects for confirming output watts (

Here’s the confusing part…
All works fine until my Bluetti starts to charge from the grid - the Bluetti AC output remains the same ~75 watts (furnace fan only) but the TPlink energy monitor jumps up to ~740 Watts.

Any ideas what is happening here?

PS-purchased my AC300 in November 2022.

@camster The fan is an inductive load, so the starting power will be high. After loading for a while, has the power become more stable?

Hello - no, the watts remain the same. Note that the Bluetti output reads expected ~72 watts for the fan running (and spikes during startup) - it’s only the TPlink sensor reads 700+ watts. This difference is the confusing part - even with the furnace on grid power the TPlink reads ~25 watts with no indication of Bluetti output - see image below. Could this just the TPlink monitor not working under these conditions?
I use a TPLink energy monitor to isolate specific output watts periodially so I know exactly where/what my energy draws are.

@camster I’m sorry I can’t confirm the problem. You can test how long it can be loaded when it shows 740W.