Use NPV for cost analysis. Compare negative NPVs, does it make sense?

Hi all, not super sure this is the right forum, but RE guys are used to NPVs, so I figured out this would be the right place to ask.

So I am trying to compare 2 options: 

option 1: buy a commodity every year for 5 years.

option 2: develop a project to produce this commodity (same quantity as Scenario 1) instead of buying on the market.

The NPV analysis will always give negative numbers, since I will be using for commodity for myself in both options, so there is no possibility for positive cash flows. 

The objective is to demonstrate the "savings" in costs as the difference between option 1 and 2. 

Does it make sense to use a "negative" NPV analysis here? Basically the NPV becomes a cost analysis, the closer to 0 the better. 

Thanks for any help :)