How much does my PC or projector consume power for real?

[MalickT]

PC - has 350W PSU
Projector - power input label shows 350W
Audio/Video Receiver - power input label 120V-240V 650W

So total power consumption should be 1350 Watt.

I connect all this to my UPS rated 1300 Watt and UPS shows only 35% load which is like 455 Watt. Even if I disconnect UPS from the main and UPS runs on batteries, it shows 35% and 15min remaining backup.

So could it be that the all my equipment actually uses only 455 Watt of power?

[microchip8]

The wattage shown on the labels is the MAXIMUM power consumption; ie, if you load your devices to the max, that's what they'll consume. In reality, power consumption is much lower. Your PC's processor doesn't constantly run at full load to consume its maximum power, neither does your receiver or projector.

[Blue_MiSfit]

So could it be that the all my equipment actually uses only 455 Watt of power?

At that particular moment in time (or whatever windowing your UPS uses to measure current) -- YES absolutely :)

Run a CPU and GPU stress test, turn your projector to its brightest setting, and crank up your amplifier and take another look. You'll see quite a lot more power being used.