Assuming that you had:
- some sort of amazing power plant on the moon that can create an unlimited amount of power
- a similarly amazing solar panel on earth that can receive an unlimited amount of power
- and an even more amazing laser on the moon that could accurately send the power to the solar panel on earth
How much power could it send before something catastrophic happened like igniting the earth's atmosphere?
- it's a nice, cloud-free day
- the moon is in perfect alignment with the earth for this shot
- the laser beam is limited to a circular area with a radius of 1 meter.