Energy Nets will significantly reduce the energy of any sail powered ships that you hit. This means that if you use it against an Ironclad with a dark matter generator, or a ship that already has all its sails destroyed, it isn't effective. However, if you do use it against a sails ship then it will reduce their energy by an astonishing 55% for 35 seconds. This has many tactical uses. The most common example is to slow down ships, especially faster or smaller ones, in order to make them an easier target to hit, thus making all your other weapons more efficient. Another use is when using a boarding ship against a faster ship, allowing you to more easily match their speed and board them reliably. It can also be used to make a target easier to ram, prevent ships from kiting you and even allow you to escape yourself. It is best to use this in a single medium weapon slot, as multiple energy nets do not stack, and therefore it is most efficient thusly.
This "weapon" doesn't cause damage to a ship, but veteran spacers fear it just the same. An Energy Net leeches energy from the solar sails that power most systems, leaving the targeted ship a sitting duck vulnerable to subsequent attack. A captain expecting to face smaller more manoeuvrable ships will wisely load a couple of these launchers.