Well heres the thing, if you buy a bad quality PSU that's not 80+ rated you're going to end up with a fire and possibly melted mining rig parts.

In general the idea of how to mine efficiently is to make sure that your PSU is never above 80% max load, if it is, then your doing something wrong(The more the load, the less the lifespan and safety of your psu) think about it this way, electricity is shocking right? The more you have it running through a powersupply, the more it needs to control and dissipate that heat, you may think oh its good enough to keep cool and regulate that heat, but in reality running it near 100% max constantly for 24/7 is going to end up making it die faster, and your other parts as well..

If you have to, just end up buying two PSU's, never just use one PSU unless its a large wattage(But make sure its a good quality PSU, Platinum Rated or Higher from a trusted brand.) I recommend using Server PSU's.


But the Max I'd say for a 1000 Watt PSU, (Don't know if its 80+ or a good brand...) I'd say off the top of my head is 800 watts max, if that, I'd go lower if it wasn't 80+ rated or a good known brand.