There’s a cruise missile warhead that spreads carbon filaments onto power lines. It was developed by the US as a radar-jamming chaff dispenser, IIRC, but a testing accident showed how easily it can mess up a power grid. The Israelis have it, and it wouldn’t take too many of these to do serious damage to the Iranian power grid. It also eliminates the problems of crossing the nuclear “red line.
What I took away fom Danon’s interview was he repeated several times that Israel has the technology to shut down all of the electricity in iran but did not mention EMP specifically. So it could be either.