In my grid-tie electric agreement, I am forced to have a separate {smart} meter for just my solar array's. The meter reads backfed power so they can bill it to me at retail, versus they pay for electricity at retail plus.
Everything related to our two solar arrays goes through this meter before it can be fed into my house. The meter reads the energy from and to 6 Enphase inverters plus the Enphase Envoy, one Sunny Boy 5000 inverter and of course, it counts the three midnite solar surge suppressors in the system {each has two blue leds on at all times}. All of that said, I read my meter every night that I am home. Since 12/17/13, or 892 days if you prefer, my meter says there has been 73 kWh's backfed by this system.
Was that 90 watt draw you mentioned a total amount for the entire night, or was it 90 watts x however many hours? Even at 90 watts for an entire day, I count that to equal 80,280 watts over the same amount of days. Divided by 1,000, it would come out to 80.28 kWh if my math is correct. That is still considerably more than I would expect from your array.
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