Comparisons are impossible based on the numbers you're giving--- size of house, quality of insulation, area of country, inside and outside temperature, etc. Your 24,000 but/hr mini-split was running at about half capacity for the time the compressor is operating from what I understand--- 3.5 kw is equal to 12,000 but/hr. I have no idea how often its cycling on/off. If its running 20 minutes out of 60 at half capacity, you're operating 1/6 capacity overall. Hopefully you've been having mild winter weather, so when you really need it to be putting out heat, you have the proper amount of capacity, without it being oversized too much.
150 watts energy use of the inside unit makes sense--- its just a small blower and some electronics.
I don't have an Emporia energy monitor, but have been thinking about getting one. I've had to replace my well pump twice in the last 4 months, and being able to track energy use could be a great diagnostic tool for such things.
I really like mini-splits. Previously had a 1.5 ton Mitsubishi in our 750 sq ft house, 2 ton LG in our current house, and just recently put in a 3 ton LG air handler unit in a new rental. In our house, we've been able to run it all summer long without guilt. It doesn't get very hot here, but is quite humid, and running it in dehumidify mode keeps it very comfortable. Cost is about $10-15 per month (100 kWh) extra electricity, which is well worth it to prevent mold and feel nice. Great in the winter too. As the primary heat source, it uses 400-700 kWh per month in our 1,700 sq ft ranch in Appalachian Virginia. Previous house used about 300-400 kWh per month through the winter.
