Electrical outlet clearance from a hot water panel radiator
I am not familiar with the NEC, but the CEC refers to usable wall space when calculating distances between receptacles; do not count the space behind an open bedroom door or under a window sill; these areas are not considered 'usable' wall space. I have found receptacles to be most usable when located closest to corners of rooms, where possible. The CEC says receptacles shall not be located above radiators; it says nothing about locating receptacles beside rads. I supose you could install them as close as practicle to the sides of the rads, but why bother? Adding an extra plug may solve your headache; they're inexpensive. I would put one in each of the three corners and one on each wall.