metering 1-phase inverter in 3-phase service? [RE-wrenches]

[Nicholas Ponzio]

Wrenches,

We're installing a Sunny Boy 5000US in a commercial building with
3-phase 208 (L1, L2, L3, N). The output of the SB will only be
1-phase, 208 (L1, L2, N). How do I meter this? Will a standard 240V
kwh meter be accurate in this application or do I need a 3-phase
meter?

Thanks in advance for any input.
-Nik