While 1/2 G gets you there in a week in the worst case scenario, the TFA actually mentions covering the 100mil km to Mars in a week, which would be during a worst case opposition. During opposition, the distance between Earth and Mars is between 54.5mil km and 102mil km depending on which area of the orbits the two planets are in. So the acceleration works out drastically different.

d = 0.5at^2 -> a = (2d)/t^2

Since we only need to accelerate for half that distance

a = (2d/2)/t^2 -> a = d/t^2
a = 102000000 / (3.5 * 24 * 3600)^2
a = 0.00112 m/s^2

So the thrust only needs to be

10000 * 0.00112 = 11.2 newtons

Resulting in a necessary power of

11.2 * 300000000 = 3.35 * 10^9 watts

This makes the power requirement much more reasonable but still quite large.