The principled BSDF had the awesome addition of emission and alpha, unfortunately it was missing emission strength making it feel rather incomplete. Instead you had to add a multiply node before connecting it to the emission color. It was kind of a paper-cut to an extent.
I took the liberty of adding emission strength to the node. It works in eevee and cycles.
The patch can be found here, thank you!
https://developer.blender.org/D4971
Many thanks to you and to Brecht!
We really have to add a custom socket for this kind of things… By default, most textures will output a normalized value, thought we might want it to be above 1, so some (possible) multiplication is still needed.
Unless we store a ‘Strength’ channel in a float format… 
Hi Secrop,
It makes sense to store normalized values for things like roughness, metal, color, etc. emission however it definitely makes sense to add a strength multiplier into the nodes.
If you want you should be able to use HDR images for strength… but that just seems like a bit of a waste of memory. LDR with multiplication is definitely the way to go for those cases.
Hey guys! Any word on this being added? It’s not in 2.81a nor the 2.82 daily builds.
Unfortunately it didn’t make it in. It was on the backburner for a while on the reviewers todo list and was never committed. I tried to maintain the patch for a while but a lot of code surrounding shaders in eevee changed, I struggled with using git and life got in the way so I moved on. I’ve definitely noticed the need for it judging from online tutorials but without the approval of the reviewers there was nothing I could do about it.
This doesn’t mean it’s not going to happen. I just got a little burned out maintaining the patch and having to rewrite it multiple times due to changes. I’ll probably return to it in the forseeable future. Its just currently on a list of projects I should probably return to when I muster up the energy to do so.
Well, I do hope it gets added. It’s something that’s need and makes a lot of sense to have.