Yes, it's sufficient for your router but only one S7. It will get pretty warm but not hot with one router and one S7 on that 16 AWG extension cord. I'm assuming your are using a PSU(s) that can also plug into 120V?
Okay. I think I will be headed out and grabbing a 12 AWG rated extension cord or better. 'pretty warm' disturbs me. I don't intend to run the router off of it. It's fine where it is. I'm just not able to feed power to the S7 from the same bedroom where the router is. The S1s weren't a problem because they were wireless. But since the S7 is a direct-line into the router, I sort of need to keep it close to the router with a long extension cord, or a bit further away from the router with a long CAT5 ethernet cable. I definitely don't want it in the hallway making all that noise. LOL At least in the office (3rd BR) I can close the door on it.
I have an old wireless router from Verizon. If I can figure out how to turn it into a bridge, I may be able to stick the thing into the garage. =]
A year ago when I got my third S3 I realized that I would max out my circuit. So I got a 12 guage extension cord for the new power supply and plugged it into an outlet in a separate room. (I verified that it was a separate circuit by flipping breakers in the main panel.) This looked like an acceptable temporary fix, but then I discovered that the outlet where the extension cable was plugged in was getting warm. A little detective work showed that many other outlets in the same room on the new circuit were also getting warm. This was a little scary.
I hired an electrician and had new dedicated point to point circuits run from my main panel to new outlets in my mining room. This made me sleep better. While he was installing these new circuits I had him replace the older outlets on the other circuits that had been getting warm. It turns out that these had been connected by pushing wire ends into the outlets to save time, rather than taking the time to strip wires and wrap the connections. Over the years, these connections had become corroded, creating resistance and thus heat.
It is not safe to use older electrical wiring lighting purposes and the occasional intermittent load without checking it out thoroughly. Older wiring may be perfectly legal and perfectly safe for typical use, but doing bitcoin mining is like using a bunch of hair dryers 24/7.