I tested underclocking-volting the C1.
The best setting was suggested by another user 2 weeks ago:
675/200 530W 803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs
FYI I have an EVGA 1300W gold.
Wish he had included F° & inHg. And is the supply on 120vac or 230vac? I'm jealous 'cause I don't get anywhere near that W/GH/s with my exceptionally cheap power supplies @ 250M/0760.