From Halopedia, the Halo wiki
Powerhouse was formerly utilized to provide alternative power supply to the rural settlers nearby, but has now been repurposed to support the military war efforts. The map is primarily designed for 4v4 gametypes and appeared in the Grab Bag and Arena playlists during the Halo: Reach Multiplayer Beta.
In team modes, such as Team Slayer, both teams spawn almost equal distances from the Gravity Hammer and the Rocket Launcher. Most players will head towards the rocket launchers first. It you also choose to go for the Rocket Launcher, it is advisable to throw a grenade or two towards the rocket launcher to wound any players from the other teams that might have been going for it too, making for an easy kill.
The Gravity Hammer and the shotgun are the most valuable weapons to have. If you can, have one player get the gravity hammer, and the other get the shotgun. To round out your arsenal, both players should also have a mid-range weapon, such as a DMR. Once you obtain these things, it is a good strategy to camp it out in the big two story building at the back of the map.