Wise Old Owl
If someone buys a 1000w psu, then will he need to buy a ups with a capacity if 1 kva or higher? Or will a normal 600va ups suffice?
Will a higher watt psu draw more current only when needed or it may pull more watts arbitrarily, thus putting more load on the ups and increasing energy usage?
No higher watt PSU will only draw current as much is needed. But higher watt PSUs usually have higher capacity caps and charging them at switch on would have a higher load. Also 1KVA UPS will only output 1000watts at 100% efficiency which is not possible. For 1000 watts you would need atleast 1.5KVA UPS to be safe. But why would anyone get a 1000 watt PSU in the first place. 550W is good enough for any personal system.