When dealing with service entrance cables on new homes, the question often comes up about underground and overhead feeders. Are underground feeds better than overhead feeds? The short answer is, yes, underground is preferable to overhead, mostly due to the protection feeders get from being buried, but underground service equipment can be much more expensive than similar overhead feeds, and both come with significant safety concerns.
Underground service cables are connected to the utility company’s pole and fed down a pipe into the ground. Then, they run horizontally through a bored hole in the ground and up into a ground-based transformer. The primary connection to the transformer is called the line connection.
The secondary side of the transformer has service cables that connect to your home's electric meter and service panel (breaker box). Alternately, there may be a pole-mounted transformer where the secondary is fed down the pole, underground, and then run to your home and up to the meter inside PVC pipe.
The advantage of the underground feed is that there are no visible wires present, virtually eliminating the possibility of damage by storms and other weather events. Underground feeds also offer a much cleaner look, since there are no unsightly power poles strung across your yard or running down the alley.
Overhead service feeds include power poles that string feeder wires from the utility company’s pole to the power pole by your home. From there, the feeder cables run overhead and connect to a service mast that runs through your roof or is mounted to the side of your home. Since the feeder cables are exposed and suspended between the power pole and your home, they are vulnerable to damage from tree limbs, heavy ice buildup, and extreme weather.
Cost of Underground vs. Overhead Feeders
Overhead feeds use triplex aluminum wire that is much cheaper and less time-consuming to install than underground wiring, which can cost about $1.50 per foot for the materials alone.
On a larger scale, utilities report that it often costs five times more to install underground power lines than overhead lines. The tradeoff, in terms of cost and other impacts, comes when severe weather events cause significant damage to overhead power systems, requiring costly repairs and economic hardship due to prolonged power outages.
Safety Factors of Underground vs. Overhead Feeders
With overhead lines, you have to watch that tall trucks, farm implements, augers, and other tall pieces of equipment don’t get tangled in them. With underground feeders, you have to watch out when you are digging. Digging around underground feeders is a disaster waiting to happen!
Before you dig anywhere in your yard, you should call 8-1-1, the "Call Before You Dig" hotline. The service will connect you to a local operator who will contact the utility companies with lines in your area. The companies will mark your lines within a few days and usually at no cost to you.
Switching From Overhead to Underground Feeder
When a utility company switches from overhead to underground service, it typically digs a hole in the front yard of the home at the location of the transformer base, near the utility pole. Then, it digs another near the home. Then it installs the service cabling by using a boring machine that drills underground from one location to another, without disturbing the ground above.
The boring machine drills through the ground and is led by a remote device that a worker moves in a predetermined path from hole to hole. Once the drill gets to its destination, a pull-tip is installed in place of the boring bit, then the cabling is pulled back through the hole and final connections are made.