The Real Cost of Living in Cos Cob, Connecticut

Connecticut's Mill Rate System and Greenwich's Number

Connecticut towns set property tax using a mill rate -- dollars owed per $1,000 of assessed value -- and Greenwich's rate for fiscal year 2025-26 is 12.041, genuinely one of the lowest municipal mill rates in the state. The number that trips up buyers moving from other states is Connecticut's assessment convention: towns assess property at 70% of its appraised market value, not 100%, so a home's assessed value (the number the mill rate is actually applied to) runs meaningfully below its market price. Working through Cos Cob's own numbers: a home that sells for $1,000,000 would be assessed around $700,000, producing a tax bill of roughly $8,429/year at the 12.041 mill rate. A $1,400,000 home (near Cos Cob's recently reported median sale price) would be assessed around $980,000, for a bill of roughly $11,800/year. A $2,000,000 home would be assessed around $1,400,000, for roughly $16,857/year.

For context on how low that actually is regionally: Darien's fiscal 2025-26 mill rate runs about 15.48, New Canaan's about 16.69, and Stamford's about 27.17 -- meaning a similarly priced home in neighboring Stamford would carry a meaningfully higher tax bill than the same home in Cos Cob/Greenwich, even though both towns use the same 70% assessment convention. That gap is a genuine, real financial reason Greenwich (and Cos Cob within it) draws buyers who might otherwise consider Stamford or other lower-priced Fairfield County towns.

No State Assessment Cap -- A Real Structural Difference

Connecticut has no statewide cap on annual assessment increases comparable to Florida's Save Our Homes 3% cap or California's Proposition 13 2% cap. Greenwich, like other Connecticut towns, revalues property periodically (state law requires revaluation at least every five years), and a property's assessed value can jump meaningfully at each revaluation cycle to catch up with market appreciation, rather than being smoothed by an annual cap. That's a real difference from Florida and California, and it means a Cos Cob buyer should ask specifically when Greenwich's next town-wide revaluation is scheduled, since it can materially change a property's assessed value -- and therefore its tax bill -- even if the mill rate itself doesn't move.

Insurance and Flood Considerations

Cos Cob sits directly on Cos Cob Harbor and the tidal Mianus River, so waterfront and near-waterfront parcels here carry real flood-zone exposure distinct from properties further inland in Greenwich -- a standard homeowners policy does not cover flood damage, and any water-adjacent Cos Cob property needs a separate NFIP or private flood policy, priced off an address-specific FEMA flood-zone determination. This research did not obtain a Cos Cob-specific or Greenwich-specific average homeowners or flood-insurance premium this session; that is a genuine, disclosed gap rather than an invented figure, and any buyer evaluating a specific parcel should get an actual quote from a licensed Connecticut agent rather than relying on a townwide or statewide average, particularly for harbor-front property.

Utilities and Everyday Cost of Living

This research did not confirm Cos Cob- or Greenwich-specific electric, gas, or water/sewer rate data this session. Connecticut's residential electricity rates have generally run above the national average in recent years across the state's investor-owned utilities (Eversource and United Illuminating), and Greenwich-area properties should be assumed to fall in that above-average range absent a specific confirmed local figure -- but that assumption should be verified with the actual utility provider for a specific address rather than treated as settled fact.

HOA and Association Costs

Cos Cob is predominantly single-family housing along with some multi-family and condominium buildings near the train station and harbor; any condominium or association-governed property here will carry its own separate HOA or condo-association dues on top of the town's mill-rate property tax, and those dues -- along with any private dock, mooring, or marina-access fees for waterfront property -- should be confirmed directly from the specific building's or association's current financials, not assumed.

Putting the Real Number Together

For a representative $1.2-$1.4 million Cos Cob purchase (near the neighborhood's recently reported median), a realistic annual recurring-cost floor looks roughly like: $10,100-$11,800 in property tax at Greenwich's 12.041 mill rate applied to a 70%-of-value assessment; a homeowners policy plus a separate flood policy if the parcel sits near the harbor or river, both requiring an actual quote given this page's disclosed lack of a confirmed local premium average; above-average Connecticut electric costs; and HOA/association dues only if the specific property is condo- or association-governed. None of these figures substitutes for an actual Greenwich Assessor's tax card, actual insurance quotes, and a current comparative market analysis for a specific Cos Cob property -- but together they give a far more honest starting budget than the mill rate number alone.