I just did an experiment of my own. This is the system I mentioned earlier.
To Recap: Transformer A, 15 kva encapsulated, 240/480 to 2400. Transformer B, 2400 to 120/240 15 KVA single bushing/MGN padmount. Transformer A is on the utility end, windings connected in parallel for 240V. I dont have a PT to use on the 2400 side, so I can only measure the 240V side and add/subract to get power measurements. No load loss when feeding A 240V is 130 watts. With transformer B connected, 190 watts total. I reverse fed the setup with a generator and got the exact same losses. The padmount is clearly quite efficient, using only 60 watts. But the Encapsulated is still way more efficient than the first transformers I used which were only 10 KVA and used 300 watts each. They were super old. The Olsun encapsulated is newer than 1993, thats all I know. The padmount was manufactured in 2009, FWIW.
This works out to about $80 per year over if I used another padmount. I got this one for about $650 delivered, and that was the cheapest I have found them. I think Ill just plan on adding a few more panels to my PV system
Ethan Brush - East West Electric. NY, WA. MA
"You can't generalize"