I don’t know the details of emonCMS, however if yours is a “Type 1” installation and the four c.t’s are each monitoring a separate consumer unit, or separate distribution circuits from a C.U., or a combination of those, then you will indeed need to sum all four.
The best way is, in the input processing of one of them, after you’ve done whatever individual processing you need, then if the value of that feed has been modified (or if you’re not sure)
Reset to original
then for each of the other 3 feeds, add
+ feed picking each in turn from the drop-down list
Log to feed which will be the total use feed.
(Note: you’re not restricted to the four emonTx inputs, you can add in an emonPi one as well - but you might see anomalies because the two devices won’t report at the same instant, so the values will relate to the powers a few seconds apart. Also, the “Reset…” isn’t needed if you have not modified the value on the way down the process list, except of course if you’ve ‘calibrated’ it with an addition or multiplication.)