The engine construction display lists the engines and shows you the starship engines that you have both the resources and tech level to build at this time. When you build an engine it remains in storage at the starbase until you fit the engine onto a hull when building a complete starship.
The display shows the cost to build this engine in megacredits and the amount of material needed. This display also shows the amount of money in the planet's treasury and materials remaining on the planets ready to be made into whatever you see fit.
You will see a graph of the amount of fuel used by the engines per light year in relation to warp factor the ship is traveling at. A low tech engine uses more fuel per light year as you increase your speed. Higher tech engines have better efficiency speed. For example, the Stardrive 3 is very efficient up to warp 3. At speeds greater than warp 3 rates at which fuel is used greatly increases.
(Also See Navigation)