They are using it (or intend it to be used) as part of their Iron Dome. So, size doesn't matter too much. Just enough power to destroy a target before it can hit its objective.

I have been in a discussion on a FB page, about how to deal with drone swarms/cruise missiles/"hypersonic" missiles in mass attacks. One thing I wondered about was how long a beam weapon, like Iron Beam, needs to be in contact with the target, to burn through and do structural damage. According to the net sifter, 2-3 seconds. Iron Dome may be fine against the primitive, aluminum, rockets Hamas used, but how about a "hypersonic" missile? Due to air friction heating, anything traveling at Mach 3 needs to have a titanium skin, or other high temperature material. That means the dwell time for the beam to burn through one spot on the target will be longer. If the missile was designed to rotate in flight, like the USian RIM-116 does, it would be impossible for the beam to be on one spot long enough. So, a titanium, or ceramic, skinned, rolling frame, missile, would appear to be immune to beam weapons.

Steve