setlevel <amount A>,<amount B>,<amount C>,<amount D>
setlevel <% of PC's level * 10>, <levels above/below PC>,<starting level>,<level cap> Sets the level (minimal and maximal) of a NPC in comparison to the player level. Using setlevel 1000,0,1,81 will make followers level along with you all the way until they and you are level 81, making starting followers such as Lydia way more useful.
amount A: the NPC's level in comparison to that of the player, based on how much percentage of the players level is carried over. A value of 1000 (100,0%) will make the selected NPC's level equal to the players level at all times. Any value below 1000 (<100,0%) will make the NPC's level lower than yours. Any value above 1000(>100,0%) will make the NPC's level higher than yours. Remember that this value is the percentage you desire multiplied by 10. So if you wish a percentage of 75, the value must be 750. Example: A value of 800 is equal to 80% of the players level. If the player is level 50, this NPC will be level 40.
amount B: how many additional levels this NPC will be above or below the level calculated through amount A. Both a positive and negative value can be used here. Example: a value of 5 will make the same NPC from above (level 40, while the player was level 50), get a total level of 45. A negative value of -10 would make this NPC level 30.
amount C: the lowest level this NPC can be, regardless of what is given for amount A and amount B. Example: if this value is set at 25, then the NPC will always be at level 25 or higher, even if the player is, say, only level 3 themself.
amount D: the highest level this NPC can be, regardless of what is given for amount A and amount B. Example: if this value is set at 35, then the NPC will never surpass level 35, even if the player is, say, level 70 themself.
- This console command will remove the default level caps on any NPC you wish. Using for example setlevel 1000,0,1,80 on Lydia, will allow Lydia to now level along up to level 80 in this case. This console command overwrite the default maximal level of that NPC for any consequent savegame you make after using this console command. However, savegames made before this point will remain unaffected. Also, NPC's seem to level up automatically after using this code.
Source: Elders Scrolls Wikia