Energy consumption here does not mean just current electricity usage. It also includes things like fueling cars and planes. Also, the 150MW/km² is apparently roughly the summer expected solar insolation; year-round average insolation comes out to ~100MW/km² per the book's numbers.

The total chart at the end came out to <https://www.withouthotair.com/c18/page_103.shtml>, with solar making up about 68 kWh/d per person.