You would probably need to go and buy your own high efficiency power supplies. You'll probably find this tricky to do at such low power levels. I've only seen good efficiency power supplies for things that draw much higher power loads.
You also need to consider what you are doing to feed the power supplies. Are you given them good power with a power factor ratio of 1 - or poor quality power with a low power factor of 0.8 - making it hard for them to be efficient. You can't expect them to perform well if you are feeding them badly.
A solar panel and storage battery could be fun to play with ...