I recently saw a question on LinkedIn that asked why we don’t use more metal utility poles instead of wooden ones. It’s a good question, and there are a lot of issues to consider when choosing between the two.
One issue to consider is useful life. On paper, the useful life of a wooden pole is thirty to forty years. However, there are plenty of poles that have lasted fifty and even sixty years. The local conditions have a lot to do with pole life. Problems like rotting wood, constant moisture, fungi, and woodpeckers can lower the useful life of a wooden pole. Steel utility poles are expected to last fifty to sixty years and can last up to eighty years. The main problem that can shorten the life of metal poles is salt and high humidity in the environment.
Another important issue is cost. Wooden poles have gotten a lot more expensive in recent years. I see prices online today between $250 and $1,300 for a 40-foot pole, with the price varying by thickness and load-bearing ability. Steel poles are more expensive, with a typical price for a 40-foot pole between $2,000 and $3,000. It’s cheaper to ship wooden poles since they weigh less than steel poles of the same height. Installation costs are generally less for wooden poles. Construction contractors and utilities already have the equipment and experience to install them. In most applications, wooden poles can be directly buried in the ground. Steel poles routinely need a foundation, which adds time and cost to the installation process. From a pure cost/benefit perspective, when looking at the combination of the initial cost versus the life, wooden poles have a lower cost per year than steel poles.
But there are other factors to consider. For example, wooden poles need to be inspected more often during their lifetime. One interesting issue to consider is that many poles don’t make it to the end of their useful life. Some are destroyed by storms or by vehicle accidents. Poles sometimes have to be relocated during road moves. A lot of poles have been replaced in recent years when they didn’t have enough room to add fiber, requiring a change-out to a taller pole. The extra useful life of steel poles is negated for poles that have to be replaced, and in that case, the lower upfront costs favor wooden poles.
With that said, there are a lot of places where a metal pole makes sense. If you’ve never noticed, poles that carry significant loading from cables usually are supported by guy wires that go from the pole to the ground (shown in the picture above). The guy wires support the poles in times of heavy wind. It often makes sense to place a metal pole in places where there isn’t room for the guy wires. Metal poles are also often preferred when really tall poles are needed.
An interesting issue to consider is emergency repairs on poles. Linemen use strap-on tools like spikes, gaffs, or climbers that allow them to climb a wooden pole. Working on a metal pole requires a bucket truck. After an emergency that affects multiple poles, it’s far more efficient for making repairs for linemen to be able to climb poles without having to wait for an available bucket truck for each pole.
When considering all of the factors, it’s pretty obvious that utilities still prefer wooden poles over metal poles. But you generally don’t have to search very hard to find places in urban markets where metal poles were the right solution.
My area has experienced more outages lately, due to aerial electric being damaged by wind. Rather than switch to metal, utilities should be underground!
the metal poles, especially in the 40-60′ range, aren’t that much more durable. they still fall over from extreme winds (bolts sheer, ground gives) and still can’t take a hit from a vehicle etc.
underground is actually not that practical in many places. the ground moves with the temperature, frost heaves, subsidence, and earthquakes etc. It’s pretty common for underground lines to break and require a length excavation to fix. As an example, I’ve been without power for about 20 hours in the last 2 weeks specifically from underground wire breaks due to subsidence.
Talk to people in PG&E’s area about underground power lines. Since they were sued for the fires their negligence started, not allowed to increase rates to cover that, but are guaranteed to be profitable, they simply went about under-grounding miles of power lines as a way to generate funds to pay the lawsuits. No I can’t exactly prove that, but I’d be willing to bet a hefty amount that’s what is going on. We have many miles of power lines that are now underground, and yet we still have PSPS events that shut the power off for 48 hours or longer, forcing hundreds of people to install generators and do sketchy DIY electrical that likely will start more fires. One small section of power lines that they deemed to be dangerous on poles had an estimated cost of over $2 Million per mile to bury! This was in mild rolling hills with very little vegetation. A: They shouldn’t need to be buried, B: It shouldn’t cost that much per mile. It’s an absolute travesty that is ruining thousands of peoples lives.
there are definitely benefits to burying lines, that just isn’t a solution to everything and it comes with it’s own caveats, including immense pricetag to install and service. And in California with all the quakes, that probably amplifies.