Getting a bigger boiler, how to keep the same run time?

[Evil_Dark]

Hi!
I'm stepping up the boiler, I currently have a 10.5 gal with a 3kW internal, I do found a 20gal. that I can adapt to my needs.
Currently, in pot still It takes around 4-5h to make a full run (heat up until the last drop taken). This amount of time is okay with my "free time", I'm afraid that with the bigger boiler I may need more time to do a run, which will be a pain for me ...
I do have a 2in reflux column that I don't use the condenser when in pot still. If I increase my heating wattage, and increase the column diameter for a, let say, 3in, can I expect to stay in the same time to distill twice more product?

I try to understand what is determining the output speed in a setup...

Thanks for enlightening me!