The 1200W rating that is listed on Spondoolies's page is for 12V DC power. In actuality, most SP10 PSUs are capable of supplying 1260W, and some can go as high as 1265W. Since the PSUs the SP10 uses are about 91% efficient at that load, that means around 1260/0.91 = 1384W of AC draw.

Horcoff requested metered billing for these machines. We measured these SP10s as consuming 1.314 kW each at the wall, which is lower than we typically see for SP10s in our datacenter (typically around 1.38 kW). However, it was much warmer then, and most of his SP10s were not hitting their PSU limits in 12V DC power. Right now, our machines are getting intake temps around 10°C, and it looks like horcoff's SP10s are hitting their PSU limits as a result (and hashing faster).