Where does the power come from?
Power tells you how fast energy is being used. Energy tells you how much was used over time. You need both, but they answer different questions.
Normal load versus a failed feed
Feed A: 20 kW + feed B: 20 kW
Remaining 30 kW path faces a 40 kW load
Follow the supply
A PDU distributes power. A UPS provides stored-energy support within its design limits. Server power supplies feed internal components.
The GPU rating is only part of the server load. CPUs, memory, fans, and other equipment also consume power.
Check the failure case
Imagine two independent feeds, each approved for 30 kW. A 40 kW rack might split its load 20/20 during normal operation.
If either feed must carry the entire load after failure, that design is insufficient. Normal operation does not establish redundancy.
Electrical design and testing belong to qualified staff. This is a calculation exercise only.
Try it yourself
A fictional rack draws 18 kW for ten hours and 6 kW for fourteen hours. How much energy is that?
Check your answer
18 × 10 + 6 × 14 = 264 kWh. It describes energy at that measurement boundary, not whether the supply can safely handle peak load.