So one horrendous inefficiency is the use of a CPA laser. The efficiency of this scheme is about as close to zero as you can get. You turn mega-joules of electrical energy into kilo-joules of short pulsed laser light, which you then use to accelerate a proton beam with less than 1% efficiency if you are lucky. Only a fraction [a few percent] of the resulting accelerated protons interact with the B11 to create fusion. So already you are operating at about 1 in a million inefficiency without accounting for a single watt to confine the B11 target.
Nor have we accounted for the thermal to electrical conversion efficiency.
Oh, and there is the problem of the cost of replacing the gratings in the CPA laser which have a very finite lifetime and are very expensive to fabricate.