1.0a or 2.1a
Does the Samsung Galaxy S5 charge at 1.0a or 2.1a?
My Galaxy S4 has a 2.1 charger as did my Galaxy Tab 3 7.0. My Galaxy S6 Edge had a 2.4a and my Galaxy Tab S2 had a 2.1 charger. I actually use a multi port 2.1 charger with the wireless charging pads for both my S4 and S6 Edge.
I'm very certain that Samsung didn't go backwards for the S5. Especially considering it's battery is comparable to either the S4 or S6 devices. The 1.0a charger may actually charge your phone albeit rather slowly, then again it may fall short and never top the battery off depending on your usage.