Do SSDs use so little power that I can add one without calculating my rig's current usage?

[Qerass]

I have an average HP rig bought a few years ago.

It has a 300w PSU (LiteOn brand). I've already added a 3 TB hdd.

Will adding a SDD be fine, or should I calculate all the power requirements?

 

[USAFRet]

Very, very low wattage, even at full power.

This from last year

http://www.tomshardware.com/reviews/samsung-840-evo-review-1tb-ssd,3567-13.html

 

[Dark Lord of Tech]

No need to calculate even if you add a few.