Actually, with Lupus, we are (in a sense) vampires. We must avoid the sun as much as possible as exposure can bring on worsening symptoms. These can include extreme fatigue, skin rashes, painful joints/muscles, and an overall feeling of malaise. So, what you are experiencing is not uncommon.
When the sun goes down and we are no longer feeling its ill effects, many of us find that we have more energy and less symptoms. The problem is that, often, this means that we get little to no sleep and no recuperative rest. So, try to make sure that you allow your body to rest as much as you can so that the fatigue does not worsen or become debilitating.
I wish you the very best
Peace and Blessings