I just run a small test on my laptop which is the latest spec and 32 GB ram and run for one hour continuously with 100 threads and 100% CPU usage and my hash rate was around 75 H/s got around 120+ Santoshi and which I think very less for the electricity we spend for running one hour. But it may be good for people where they get cheat electricity.
I think the best idea is to run it in the background while you are using your PC for something else so it's only costing a little extra electricity in the CPU. Doing this it is running at about breakeven on my 4-year-old i5 so something more modern like you are talking about should be running in profit.