PR02x port replicator, 90w?

Can I get by using a 90w power adapter with the port replicator or do I need the 130w one?

 

It is recommended that you use a 130W for a laptop up to 15.4 inches and a 210 W for a larger display, see https://support.dell.com/support/edocs/acc/eapr/en/ug/EPortPlusUG0D.pdf

 

What system?

I just purchased a 2nd PRO2X docking station, and it didn't come with a power supply. I thought I'd try it with my existing 90W adapter before purchasing a 2nd 130W adapter as well, and I haven't had any issues with the 90W adapter, the PRO2X, and my Dell Latitude E6500. I would still recommend the 130W adapter if you can get one for a reasonable price, but the 90W adapter seems to suffice.

Really, I can't see that anything on the docking station would consume up to an extra 40W of power, unless some serious power is drawn from all the USB ports. (Though, assuming perfect efficiencies, a max 500 mA drawn from each of the 10 available USB ports (6 on docking station + 4 on laptop) x 5 V = 25 W.)