100w power adapter for 140w MBP

[miamialley]

I have a 100w power adapter. Is it okay to use for a MBP which comes with a 140w? I know it won't always power it sufficiently, but is there a reason I should not use an adapter that supplies less than 140w?

 

[mfram]

It's fine. The 100w one just won't support the 'fast charging' feature.