Healing abilities vs. CR

If I wanted to change the healing abilities of celestials or the priests stat blocks in the new Monster Manual, how much is the challenge rating affected? For example if I want to increase the number of times the priest can use its divine aid bonus action would I then need to change the CR and/or HP? Is there a rule for this somewhere?

The guidance from the 2014 Dungeon Master's Guide for making monsters doesn't list anything for healing abilities, but does suggest for Regeneration-like abilities to "Increase the monsters effective hit points by 3 x the number of hit points the monster regenerates each round." Note that this isn't about increasing it's actual hit points, you just treat it as having a high hit point max for determining CR.

For example, if you have a monster with 100 hit points, but it can regenerate (or in this case heal) an average of 10 hit points per round, you treat it as having 130 hit points when determining CR.

How much this will change the monsters CR depends on a lot of factors, but in most cases it won't nudge the CR more than one place, if that, unless the healing is a huge amount. 

And if the healing is consistent too, like Regen.

A healing effect that takes an action is generally 'worth' the same as an attack that does the same damage, so if their healing is less potent than their attacks it may not change CR at all.

Debatably the heal is even worth a bit less, all other things being equal, given that 5e doesn't have any RAW mechanisms for combat fatigue to allow for attrition tactics without some reactive damage element.

D&D healing is NOT MMO healing. You're not supposed to keep everyone at max HP constantly. Healing does not outpace damage. Instead healing is about getting people back up.

Quote from l1enangake >>

D&D healing is NOT MMO healing. You're not supposed to keep everyone at max HP constantly. Healing does not outpace damage. Instead healing is about getting people back up.

True but - 

While the "don't top off" approach is clearly the design intent for 5e/2024, it highlights the broader "dumbing down" of the game. It’s reached a point where building a balanced party is labeled "metagaming" in some circles—which is ludicrous. The idea that adventurers wouldn't want a dedicated tank, healer, DPS (Caster), and utility specialist (Bard/Rogue) ignores the tactical roots of the game.

We’ve seen a shift in the player base—driven largely by the "actual play" era—where the focus has pivoted so far toward performance (Critical Role Style) that the underlying mechanics and dice-rolling have become secondary.

The current system makes the healer role feel unrewarding because, at best, you’re just "yo-yoing" unconscious allies back into the fight. It’s why most veteran DMs I know significantly buff healing output once they hit Tier 2. It restores actual strategy to the game, moving away from the "I’ll just wait for them to drop" mentality and back toward meaningful support play.

Quote from The_Ace_of_Rogues >>

Debatably the heal is even worth a bit less, all other things being equal, given that 5e doesn't have any RAW mechanisms for combat fatigue to allow for attrition tactics without some reactive damage element.

I was mostly talking about how CR math works, not trying to adjudicate whether that math is actually correct -- generally speaking, +X damage per round and +X heal per round will have the same effect on CR.

Ah, fair

Thank you all.