Necroposting ftw! (still, the ship's still around in 2015 after a 45 million USD repair in 2013, so who knows who may read this in the future :))

Right, on with it!

The Emma Maersk captain will typically aim to have her run as energy efficient as possible, which averages around 1700 gallon/hour, or roughly 6 tonnes/hour.

Using a price of 450 USD per tonne of marine diesel, this reduces the yearly fuel consumption to around 20 million USD (I added a few million just in case they need to fire the auxiliaries more often).

With the 1200 tonnes of fuel saving due to the silicone based paint, adding up to around 540k USD, the savings are more likely to be in the neighbourhood of 2.7%.

While this still sounds like a drop of water on a hot plate, 540k is still 540k that we, the consumers, don't have to cough up for our products.

As for the question if adding sails would make it more fuel efficiency:

Like geeklord mentioned, burning things is easy. We already have technologies in place to provide us with fossil fuels that are known to have enough oompf to bring a ship with a total weight (own weight + cargo) of around 320k tonne (320000 kilo) into motion and keep it going at a certain speed.

For sails to take care of some of that speed, considering the size that the sails would have to be, the masts that would be needed to hold those sails up, the times per week/month/year those sails could actually be deployed, I am pretty sure that the added weight and costs, set off against the fuel savings during the times the sails would actually be used (which is only between certain min and max windspeeds), adding sails would add to operational costs of the ship while doing very little to actually make the investment worthwhile, and I doubt that any such investment would pay itself off during the lifetime of the ship.