Only in New York is a private ­island cheaper than an average apartment.

Savvy city dwellers looking for a new home might want to consider buying their own private island less than two hours north in ­Putnam County.

While the average New York apartment costs more than $1.4 million, Willow Island on Putnam Lake in Patterson costs $995,000 — and comes with a three-story, four-bedroom home.

In contrast, the average price of a two-bedroom Manhattan apartment is $1.35 million — and $2.63 million for a three-bedroom.

The one-acre property also comes with its own special New York City provenance. The house was built by one of the engineers who created the Holland Tunnel.

The island is an hour-and-a-half commute from New York City, says listing broker Uri Hanoch, of Douglas Elliman.

But the deal does come with a hitch. The new buyer will have to row home each night from Patterson, where the property comes with a two-car garage.

The sellers are retired ad exec Larry Plapler, 79, and his wife Amelia, 70, who first put the island on the market in 2010 for $1.5 million.

Plapler — who has made the weekly drive with his wife, Amelia, and family for the past 38 years — once told The Post that the getaway makes him feel a world away from his Upper East Side home.

The 1¹/₂-bath home is 5,600-square feet and comes with 48 open-view windows. The home includes a floor-to-ceiling stone fireplace and an artesian well. There’s a guest cottage and a private garage for your boat, according to the listing.

“Access,” according to the listing, “is a quick five minutes by a rowing boat or 5 mph electric motorboats. Canoes, kayaks, rowboats and sailboats are also welcome.”

Gas-powered boats are forbidden on Putnam Lake, on the Connecticut border.