You lose your Card (generally, unless your team is super bad) and Ult Charge for sure. Not sure if the other is measured in 10 minute intervals or not.
Also it only matters below diamond anyway. You should focus on getting the win regardless. SO switch if you need to counter something. Some SR is better than NO SR.
Switching roles will generally cause you to get bad stats, and because the SR system cares about stats (it shouldn’t), this does indeed penalize your SR.
i am assuming the system is actually smart enough to compare player stats with mins played taken into consideration.
The powers to be, wont give us ANY official PLAY RULES on competitive.
THEY HAND OUT bans based upon mob rule. NO CLUE how they can. When we do NOT have an OFFICIAL rules page on how Competitive play must be done.
That said. Everyone is ALWAYS bullied into switching from their characters. 
and with that said. Competitive will ALWAYS be a mess.
I wouldn’t give them too much credit. 
A game that rewards switching
that punishes you for switching
sounds about right?
idk I still get the same high 20’s sr in wins even if I switch around roles
If he is correct I think you would feel the impact most with a switch from dps to healer. As they are measured so differently.
same and if I lose I do lose way more than switching since at most it reduces my max SR not actually losing SR for switching and winning
hmm well the other day I was bastion on junkertown attack for pirateship but on defense I believe I played mercy after (dropped from gold dmg/elims/obj time to bronzes/no medals but got to bronze healing I think) and I still got 27 or 28 SR.
I know in other instances I’ve swapped off damage to a healer and didn’t notice a loss in SR gains for winning.
Idk maybe he just performs poorly on healer roles?
Oh, hm I don’t think I paid any attention to how it affects my sr in losses. Ill keep an eye on that
Yeah while it is secret, it is impossible to know for sure expect based on our own experiences, I also have not seen a difference, and I usually am the one swapping to counter the enemy team carry. I play to win, so it’s not really an issue for me.
SR is an afterthought.
Oh it doesnt seem to factor in my loses. thats not what I was saying. Sorry about the confusion.
what i meant was a loss is a loss and I lose SR but if I win even when switching it’s still a net positive
now that you mention it I too am curious about the effect on the loss
I believe the performance based SR system penalizes you if you switch more than once.
But i dont know really, i just remember it being a thing back when PBSR was a thing above diamond.
One time I saw an Ana not shooting to heal the team. I asked why they weren’t shooting and they said “I didn’t want to miss hard shots, it will lower my stats”. I don’t know if it’s true or not, but the problem is that some people think it matters. Either tell people how the performance based SR works or remove it.
Still don’t get the phylosophy from the devs, i mean they admit its stupid. 
Same for winston mains suddenly playing widow or sombra. They said, a bad tank could still be a good dps as example.
But the system thinks he’s dia (reinhardt) and you have now a low plat soldier.
Jeff confirmed these flaws.
It is possible to have worse SR gains/losses when attempting to play a role or specific hero you are not familiar with, especially if you are in Platinum and lower ranks where a small factor of performance-based skill rating adjustments apply. A full guide explaining this is available here.
Thanks all for the replies.
I play a lot of support and sometimed when we have healers I go dps.
Quite often after a death or two healers suddenly go dps and we then have no healers! I often switch to healer at that point.
Shame you can lose out trying to help but switching!
lost 5 games in a row trying to heal potatoes
the 6th game i stopped caring and made careless deaths and resulted in a win.
And every Capture point map goes like this…
1 team destroys the first round, 2nd team destroys the 2nd round. 3rd round is a hodgepodge of destroying usually resulting in 99% games.
i can asure you its not smart enough. then you would be gotten a card if you did good on both healer and tank ,feks. cards say nada. i have seen the worst of the worst moiras getting cards because she screw here team over and goes dps. heals here team after fight" if you survived". might aswell grabbed a hp pack
There’s zero way to tell.
No one knows the base SR for a win or loss.
No one knows the performance stats that are taken into consideration.
No one knows max./min. allotted for performance.
No one knows where the impact from performance starts/stops. (I don’t mean SR tier. Instead, the statistical value that has to be met before it has any impact)
No one knows how these stats are tracked/measured. Is it per 10 minutes, per minute, per game?
No one knows the impact that team averages has, and intervals that it goes up.
No one knows if there’s an impact to gain/loss if you are above or below your team’s average.
If so, no one knows at which points it makes a difference.
Essentially, everyone is Jon when he first goes north. “You know nothing Jon Snow.”