Prius C & 14" Rims for Winter Tires

I have a question about winter tires that I am trying to figure out. I recently bought my first Prius! The 2014 Prius C with the premium upgrade package. I love the car but it comes with 16" rims. The specs for the rims are P195/50R16. While I have very awesome summer tires that give me excellent MPG I am having a very hard time finding decent winter tires for this rim size.

From my previous vehicle I have very good winter tires (or at least ones I like) Michelin Defender XT's but they are on a 14" rim. Specially they have a rim size of 185/70R14. They only have about 5000km of wear on them and so I would love to reuse them if possible. I have several online tire size calculators and none of them seem to provide me any information suggesting that this is a horrid idea but I have to admit I do not fully understand what they are all saying so I was hoping that someone here might be able to help me to figure out if this would be an okay idea again.

The main reason for asking is that re-using tires that cost $150 a pop and buying new 14" rims for them is much cheaper than having to buy 15" rims and new tires.

An example calculation that I did can be found below:
[Broken External Image]:http://imgur.com/BhHNdgw

 

Hey,

I am still in the breaking in period but on average I am getting around 4.7 L/100km or ~50MPG. I have had drives as good as 3.2L/100km (highway & city). This is still not close to the 3.6/4.0/3.8 l/100km or the 78/71/74 MPG I was promised though. That is using the stock alloy rims that came with the car.

* I just looked up to USA EPA specs on the 2014 and they are 53/46/50 MPG which if that is the case then my car is dead on to their promised performance.

I just checked with my local tire store and they said using 14" rims should be fine I would just see a 2% difference on my speedometer (shows 100kmph actually doing 98) but I am okay with that. I will probably also go with cheaper alloy rims in the winter as well because I want to keep the rotational resistance due to the extra weight of steel rims low (not sure how much of a difference this would actually make still looking into that) but the acceleration is slow on the C all ready don't need to add more making electric acceleration even harder (slower).