More efficient to run Archer C7 (dual channel) router in single band?

[Kaiju]

I have an Archer C7 but all the devices that use the wireless connection are too far away to make the most of the 5Ghz band.

Would it be sensible to simply run single band (2.4Ghz) as I won't be using the 5Ghz band?

Is there for example a performance hit when having both bands open?

 

[Kaiju]

Thanks for clarification.