[kragen]

If this is due to solar, though, this is some kind of perverse market malfunction—somebody's getting paid to keep their solar farms turned on and pumping power into the grid even when the grid operator is having to pay someone else to burn it up. Negative LMPs can be real with coal or nuclear generation, because their ramp times are measured in hours or even days, so you can't just turn them off at night when you don't need them. But the ramp time of a PV panel is about 100 nanoseconds. Short the panel out with a MOSFET (or, more dangerously, open-circuit it) and it stops producing power in under a microsecond. There's no fundamental reason for PV to drive prices negative.