My T440p's power supply is rated 6.75A and 20V DC secondary, that's 135W, not 90W.
The power consumption depends on what you are doing with it, and if you put a 2nd HDD or SSD into the optical drive bay (which is what I did), connect USB devices, etc.
I plugged it into a Wattmeter. My T440p with the Core-I7 4900MQ, 16GB of RAM, and a 256GB and a 1TB SSD draws between 30 and 40 Watts on the primary side with light load, like browsing and word processing. This is while on a wired Ethernet connection. But it jumps around quite a bit.
If you run benchmarks, it will certainly max out the 65W power supply. Reviewers say that the max power consumption with load is over 70W. If office work is all you do, 65W may suffice, even after factoring in the efficiency of the power supply that I would expect to be in the 80% to 90% range.
By the way, the T440p has new rectangular power connectors. If you were hoping to reuse a power supply from last year, forget it!
I ordered a port replicator from Lenovo with it that also came with the big power supply. Yes, they are big and heavy. I would not take a chance and buy a smaller one for mine.