"Hi gb

The oft-quoted 85 days VASIMR to Mars mission (sans 30 days spiralling out of Earth's g-well) needs 12 MW of power. Beaming to Mars via laser might be doable, but it'd be quite a spread beam by then. Solar option would need 2.25 times 12 MW of collection power at apohelion. Landis designed a system using L'Garde inflatables as part of an SPS, and estimated it could get 100 kWe per individual 24 kg power-units. Thus the 12 MW at Mars power supply would mass ~270 x 24 kg = 6480 kg. Eminently doable, but it has to be pointed at the Sun and that might complicate matters. Might get 1 kW/kg specific power out of a solar-powered system, after accounting for structure, which for Mars missions would be adequate. Further afield will need nukes. "

Well, with the solar power you could beam less distance, if you had a separate unit in orbit between Earth and Mars [so it's only in the right location for a limited time period]. One could also have something at Mars L-1. Or both.
So the vehicle making the transit just receives microwave or laser beamed power. And count on any location beyond perigee to only get say 1/4 or 1/10th [or even 1/1000th] of the beamed energy.

So, basically you size your microwave receiver, to get power beamed from the earth surface [which is getting it's power at 5 cent kw/h from grid]. So question is how far could that system pump out power in the "general direction" of spacecraft [as it leaves earth and nears Mars] and/or to some relay point which relays to craft. Then have other nodes which can provide a constant but much lower total watt power to the vehicle when needs to decelerate near Mars.

In terms of total tonnage put in orbit, considering you want to get a craft to Mars very fast. Your sources of energy don't need much velocity- you using speed of light of the beams to get the power to the fast velocity craft.

So, suppose you had 1/4 of mass in antenna, 1/4 in motor [VASIMR] and 1/2 in propellent and it's structure. The power you get from Earth is practical free compared to the cost of energy from the other sources- and those other sources could cost far more the than craft and still be fairly cheap. The road costs more than a car.