Ahhhhh yes, another sufferer here.
Poor DH is also surprised to find himself exhausted after doing, broadly, fuck all, today.
He has a special routine for letting me know.
He begins with doing the ‘actions’ – yawny, wide-eyed surprise face. He might puff out a breath as though caught off guard by this unexpected exhaustion. He might even freeze in his tracks with a hand on a drawer where the screwdrivers live as though he was genuinely about to do something useful but, to his great disappointment, finds he can barely stand, so exhausted is he.
This is ignored by me, so then he will suddenly flop down onto a chair as though he is gutted he can’t go for that 10K run. This is done with a sort of flopping-flourish and usually accompanied by gentle eye closing for a few seconds. He can't keep them closed though because he has to make sure I am aware that the charade is playing out.
As long as I am stoic and ignore this, he will look at the cooker and ask “Is it really only eight thirty?” as though he has had major surgery whilst suffering jet lag. I either treat this as a rhetorical question or I might distractedly say “Oh I think it might be a minute slow”. Often at this point, for a bit of fun, I will ask if he fancies nipping up into the loft so we can get ‘that box/those bags/anything I can think of’ down. This is met with a look of sadness. He SO wants to but he really has a bad case of The Tired.
At this point, he can’t really hold out any more and has to share his Tired with us all. He might say “God I really am extraordinarily tired. Bone tired actually – I might need to lie down”. I usually can’t help myself and will often tell him “You do that. I’m just going to take the bins out/move the chest of drawers. But once I did say, “Oh do you mean like when I used to get knackered in the first trimester with DC2? When I could almost sleep on my feet” and he gratefully replied “Yes! Like that! Weird isn’t it?” 
I left the room.