Huge amount of variables involved. Shoes, tires, tire pressure, tubes, water bottles, helmet, clothing, cables, terrain, wind, road surface, shaved exposed skin, etc. are just a few of the things that are involved. I can sit up on my road bike (2012 CAAD10 with 50mm wheels) at 250 watts and be going 19 or so mph. On my tri bike in a good position I can do 25+ mph on the flats at 250 watts. In the drops on my road bike & holding a good position I am generally about 2 mph slower than the tri bike.

My guess is that you may have quite a few aero things to improve.

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