The Real Cost of Owning on the Other Casco Bay Islands: What the Numbers Do and Do Not Tell You

The Real Estate Picture: Two Confirmed Numbers, Three Honest Gaps

Chebeague Island, the largest of these five islands, has a Zillow typical home value (ZHVI) of $666,975, as of data through June 30, 2026 -- down 1.8% over the past year.

Long Island's Zillow ZHVI stands at $609,323, as of data through January 31, 2026 -- down 4.2% over the past year, the steeper of the two confirmed year-over-year declines in this group.

Great Diamond Island and its redeveloped Diamond Cove neighborhood are a different story. Zillow maintains dedicated listing pages for both "Great Diamond Island Portland" and "Diamond Cove Portland," showing 25 recently sold transactions, but a specific current ZHVI figure for Great Diamond Island could not be independently confirmed here. Diamond Cove's own developer- and HOA-affiliated site lists properties directly for sale and rent, and is worth checking alongside Zillow if the former Fort McKinley community is on your list.

Little Diamond Island and Cliff Island do not have a reliable ZHVI or median-sale figure at all, and that is a real fact about these markets, not a research shortfall to apologize for. Little Diamond has as few as 3 total housing units by one demographic estimate. When a single-digit handful of sales makes up an entire year's transaction history, a "median" is not a meaningful market signal, and this page will not manufacture one for either island.

The pattern across all five islands, confirmed and unconfirmed alike: a genuinely high share of vacant or seasonal housing stock, and -- per 2025 Portland Press Herald reporting on Maine's unbridged islands -- a rising share of purchases by off-island and out-of-state buyers converting year-round homes into seasonal retreats. That shift is itself documented as a driver of the islands' affordability crisis, not just a side effect of it.

The Ferry Is Not Optional -- and Its Fares Are Currently Under State Investigation

Every one of these five islands depends on Casco Bay Lines for people, groceries, mail, medical trips, and building materials. As separately confirmed directly on the carrier's own site, current peak-season (April 18 through October 12, 2026) round-trip adult fares are $16.00 (child, senior, and disabled fares are $8.00); off-peak-season (October 13, 2026 through April 16, 2027) round-trip adult fares are $8.00 (child, senior, and disabled fares are $4.00). These are flat rates that apply identically across all seven served stops -- Peaks, Little Diamond, Great Diamond, Diamond Cove, Long, Chebeague, and Cliff -- regardless of distance or crossing time, so the roughly two-hour round trip to Cliff Island costs exactly the same as the short hop to Peaks Island.

Chebeague Island is the one exception to a single-operator setup: it is also served by the Chebeague Transportation Company (CTC), which runs a roughly 15-minute passenger route from Cousins Island in Yarmouth to the island's Stone Wharf, plus a 43-foot vehicle and freight barge (April through November, by reservation). That two-operator, two-route structure is unique among these five islands and is worth factoring into any Chebeague commuting or freight-delivery plan.

The current fares above sit inside a genuinely live civic dispute. The Casco Bay Island Transit District (CBITD), which operates Casco Bay Lines, proposed raising peak-season round-trip adult fares from $14 to $17 (a 21% increase), with 30-day passes rising from $48 to $51 and off-peak daily fares from $7.20 to $8 -- citing rising fuel, labor, vessel-maintenance, insurance, and regulatory costs, and projecting roughly $559,000 in added net revenue. It was the second passenger fare increase in three years, following a 2024 increase (the first in 15 years) and a separate 2025 vehicle-fare increase. Hundreds of island residents filed a formal petition citing both affordability concerns and improper public notice, and Maine's Office of the Public Advocate supported a state review, noting that repeated fare increases had placed a growing financial burden on low- and moderate-income island households. On June 16, 2026, the Maine Public Utilities Commission unanimously voted to open a full, formal adjudicatory investigation into both the financial justification for the increases and the rate-setting process itself; the new fares remained in effect for the summer season while that investigation proceeded, with the PUC retaining authority to modify or reverse them. The $16 figure confirmed directly on the carrier's own current rates page does not exactly match the $17 figure discussed in the spring 2026 proposal coverage -- that likely reflects the gap between a proposed number and an adopted one, or a later adjustment, so re-verify directly with Casco Bay Lines before budgeting around either figure.

Seasonal Water, Barge Construction Costs, and Why "Off-Grid by Ferry" Has a Price Tag

Little Diamond Island's population is small enough, and its infrastructure thin enough, that it functions as a seasonal retreat rather than a year-round neighborhood: the island's water supply is shut off in winter, which is explicitly why permanent habitation there is so limited. That is a real, structural cost fact for anyone considering it -- not a quirky footnote -- because it means "owning on Little Diamond" and "living on Little Diamond in February" are two different propositions.

A July 2025 Portland Press Herald investigation into Maine's 15 unbridged islands -- explicitly including Chebeague, Long Island, and Cliff Island among the Casco Bay islands examined -- found that island construction costs run roughly 30% higher than mainland costs, driven by barge transport and infrastructure needs, and that land supply is further constrained by conservation easements. The same reporting found a median island resident age of 56, against 44 statewide, and identified wealthy outside buyers converting year-round homes to seasonal use as a direct driver of the affordability squeeze described in the section above.

Solutions being tried on the ground are real and named, not hypothetical: modular home construction on Chebeague, Long Island, and Vinalhaven; converting single-family homes into multi-unit rentals on Cliff Island and Isle au Haut; and MaineHousing's dedicated Affordable Housing Initiative for Maine Islands, which has funded 49 units across 10 islands with grants of up to $840,000 per project. Chebeague's own Chebeague Island Community Association (CICA) has run affordable-housing projects for over a decade: a modular duplex at 43 School House Road, built with a $350,000 MaineHousing grant and installed in May 2012, occupied by two island families by that fall; a 2013-2014 rent-with-option-to-purchase house at 226 South Road; and a second modular duplex at 553 South Road, on land donated by Stacie and Toby Webb, built with Dirigo Homes, installed in May 2025, with tenants moving in during fall 2026.

Putting the Real Cost Picture Together

None of this is a reason to avoid these five islands -- it is the honest, structural picture underneath whatever number appears on a listing. Chebeague and Long Island have real, sourced ZHVI figures you can start from; Great Diamond, Little Diamond, and Cliff Island genuinely do not, and any figure you see quoted elsewhere for those three should be treated with real skepticism until you can trace it to a specific, dated source. The ferry that connects all five islands is not a fixed cost either: current fares are confirmed directly on Casco Bay Lines' own site, but they sit inside an active Maine Public Utilities Commission investigation that could change them, and Chebeague's added Chebeague Transportation Company route is its own separate cost and schedule to check. And island-specific factors -- Little Diamond's winter water shutoff, barge-driven construction premiums, and a genuinely rising rate of seasonal-conversion purchases -- all affect what ownership costs beyond the sale price.

Before making an offer on any of these five islands, confirm current property tax mill rates and assessed values directly with the relevant town or city: the Town of Long Island and the Town of Chebeague Island each run their own assessor's office, while Great Diamond, Little Diamond, and Cliff Island are all part of the City of Portland and are assessed through Portland's own citywide system. Check current Casco Bay Lines fares and schedules, and Chebeague Transportation Company's schedule if relevant, directly with each carrier rather than assuming last season's numbers still hold. And work with a Maine coastal real estate agent or broker who specifically handles Casco Bay island properties -- they will have current, first-hand numbers for Great Diamond, Little Diamond, and Cliff Island that no general source, including this page, can substitute for. Nothing on this page is legal, tax, or financial advice.