I think you're misunderstanding the author. From the article:
Sun generates 12VDC via the solar panel
Solar panels push power to a battery
The battery or the solar panel push 12VDC to a DC to AC converter (20% loss of power).
AC is distributed throughout the house
Many devices then convert the power BACK to DC (20% loss of power)
He doesn't claim there's an energy loss between the solar panel and the battery. The conversion happens when the power comes out of the battery and gets distributed to all your appliances, many of which promptly convert it back to DC.
However, if the loss from each conversion is only 5% instead of 20%, the whole issue becomes a lot less important.