What Maine's island grids know about the price of a kilowatt-hour

The island math, up close

Open a Central Maine Power bill on the mainland and you will see the cost of a kilowatt-hour split into supply (the electricity itself) and delivery (the wires that bring it to your meter). For most of us the total lands somewhere in the twenties of cents per kilowatt-hour, give or take, depending on the month and your supplier. On a few islands off the midcoast, the same unit of electricity costs a good deal more, and the people who run those systems have been doing the honest arithmetic of a small grid for decades.

Monhegan, Isle au Haut, Vinalhaven, and North Haven are not on the big grid the way Portland is. Some draw power through a submarine cable from the mainland; at least one still leans on diesel generators that have to be fed by boat. These are small, consumer-owned systems, co-ops and plantation power districts that answer to a few hundred meters and a board of their neighbors.

That makes them something like a laboratory. When an island co-op weighs a battery against another cable, or wind against diesel, it is doing in plain view what the rest of ISO New England (the regional grid operator that keeps supply and demand matched across six states) does behind layers of markets. This desk thinks the island math is worth reading closely, because it shows the true cost of a kilowatt-hour with the padding stripped off.

Why an island kilowatt-hour costs more

Start with Monhegan, roughly ten miles out, where the power district still runs on diesel generators fed by fuel that arrives by boat. Spread the cost of fuel, machinery, and a handful of staff across only a few hundred year-round and seasonal meters, and the price per kilowatt-hour climbs well above what mainland customers pay, several times over at last public report. There is no hiding a fixed cost on a small system; everyone on the island pays a share of the same generator.

The cable islands tell a quieter version of the same story. Isle au Haut draws power through a submarine cable run from Stonington, and Vinalhaven and North Haven share cables as well. A cable spares you the diesel, but it is a large capital item that ages in salt water and someday needs replacing, and that looming cost sits under every island rate whether or not it shows up on this month's bill.

What the co-ops actually tried

Fox Islands Electric Cooperative, which serves Vinalhaven and North Haven, put up three wind turbines of roughly 1.5 megawatts each around 2009, a project meant to cut the cooperative's reliance on power bought over the cable. The turbines did generate real electricity, but the effort also drew years of disputes among neighbors over noise and over whether the promised savings showed up, a reminder that even good island math can disappoint when the wind and the market both move.

Isle au Haut went a different way, adding a solar array with battery storage and encouraging heat pumps (electric heaters that move heat rather than burning fuel) to shave the island's peak demand and lean less on the cable. Monhegan, for its part, became the name people on the midcoast associate with offshore wind, because the state set a floating-turbine test site in the waters off the island years ago; that University of Maine demonstration has slipped repeatedly, and this desk treats any near-term date for it with caution.

What the islands teach the meter on your wall

An island lesson for the rest of Maine is that a kilowatt-hour is never just the fuel. It is the wire, the storage, the standby capacity for the coldest night, and the small number of hours a year when demand peaks and the whole system has to be sized to meet it. Batteries and heat pumps are attractive on an island precisely because they attack those peaks, and the same logic is starting to reach mainland bills through ISO New England's winter planning.

There is also a governance lesson. The islands have run consumer-owned power for generations, the model Maine voters weighed statewide and rejected at the ballot in November 2023 when the Pine Tree Power proposal failed. Whatever you made of that vote, the islands are a standing, unglamorous example of neighbors owning the poles and the generator and paying the true cost directly, with no one else to send the bill to.

Worth watching this month

1. Efficiency Maine's heat pump rebate terms, which change from time to time, are worth checking before the first hard freeze if you are weighing a unit this winter.

2. The Maine Public Utilities Commission's docket list is the place to watch for any rate filing from a consumer-owned island utility, most of which are routine but occasionally matter a great deal to island ratepayers.

3. The University of Maine's floating offshore wind effort in the Gulf of Maine posts periodic updates, and any firm construction or test date near Monhegan would be genuine news after years of delay.

4. ISO New England's winter outlook, usually issued ahead of the cold season, signals how tight the regional grid expects to be and whether cold-snap reliability is a concern this year.

5. The Governor's Energy Office occasionally updates its island and offshore wind pages, a routine source that is still the first place a state policy shift would surface.