A 20 A single receptacle will cost more than a 15 A duplex.

Just use a 15 A duplex.

It's convenient to have a duplex receptacle up there in the cabinet, a lot of times people have devices that need to be plugged in to charge a battery that can be stored inside the cabinet.

I don't know the current codes - but if the microwave calls for a 15amp circuit are you really not allowed to install a dedicated single 15amp outlet for it?

I don't know the current codes - but if the microwave calls for a 15amp circuit are you really not allowed to install a dedicated single 15amp outlet for it?

Absolutely, what else would you install? But I think you have a typo in there. What you're asking is if you can install a 15 amp receptacle on a 20 amp circuit. The answer again is yes. The logic is that you can plug a lower demand appliance into a higher amp circuit. Certainly you could use a 20 amp receptacle but they're typically more expensive so why waste the money.

"I don't know the current codes - but if the microwave calls for a 15amp circuit are you really not allowed to install a dedicated single 15amp outlet for it?"

It actually comes down in many cases to the exact wording of the installation instructions for the MW.

They almost always 'recommend' a dedicated 15 A circuit (or more) for home size units.

A very few commercial models 'require' the dedicated circuit.

What I was questioning was the OP's assumption that he _had_ to run a 20amp circuit for a microwave oven that called for a 15amp circuit.