What wattage is right for me?

[MarineElectrician]

Does anyone know about how much watts I need for my rear-hub direct start motor?
I weight 175lbs(80kg) and I want it to be able to hit up to 50mph (80km/h) on a flat surface, and be able to hold 30mph on a uphill slope (not very steep).
I was thinking about if a 1kW motor or 1,5kW would work, or do I have to go bigger? And I was wondering if it is necessary to have a motor on both the front and rear wheel, or if it's enough with the rear.
And if you are so kind, do anyone know about a motor that could fit my demands, and that are shipping to Europe?

 

[dogman dan]

About 4000w possibly 5000w to go 50 mph.

 

[MarineElectrician]

About 4000w possibly 5000w to go 50 mph.

That's what I calculated also with the calculator links posted above, but I've been reading a little on forums, like this thread: https://endless-sphere.com/forums/viewtopic.php?f=5&t=14786 and wondering if a Crystalite 3kW H4080/4065 rear hub would work for my bike. This is the one I'm looking at: http://shop.crystalyte-europe.com/product.php?productid=16572&cat=295&page=1

On a regular basis I will be riding it in the city with quite low speed, but I want it to be able to go fast when I'm alone on an open road. It doesn't really matter that mutch if it goes fully 50mph, but I need it to go at least 40mhp on a flat surface.

And is there anything special I should keep in mind when buying my hybrid bike that I'm going to install the motor on, to make sure that this excact motor will fit my bike? Wheel size I guess, anything else I should check?