> I doubt the expense argument too

Seattle buried some power lines in 2007. It cost about $2500 per foot - and the way that article is written, it doesn't necessarily cover the whole cost.

A much cheaper proposition by Hydro Quebec was floated in 2017. And by "much cheaper" I mean it was $4.2 million per mile instead of the $13 million per mile it cost in Seattle.

Generally speaking, burying powerlines costs about 10x as much as running them overhead, and the numbers in that article come out to be just under $4 million per mile.

Even the most recent prices I can find, for PG&E, put a number between $1.5M and $3M per mile with the costs being paid by the people who are served by the electric utility, and the costs being dependent on how much the process is.

The reason that housing developments are putting utilities underground is that burying power cables rated for 200 amps when you already have trenches for water and sewer doesn't add a huge expense over running the cables overhead, since most of the cost, at that point, is the cable. Because for residential installs, the cost per foot is only about $8, unless there's local regulations and rules that make it significantly more expensive, because there's limited capacity in underground conduits and cable vaults.

And again, all of these costs are basic costs. They don't account for the type of terrain we have in NH. The closest we could get would be the cost from Hydro Quebec but even there the soil is much flatter and they weren't going to have to do any horizontal drilling to make it work - That was all using existing infrastructure for buried cable. Horizontal drilling is much harder when you have as much rock in your soil as we do.