Electric motor assisted bicycles have been banned in the State of New York and are not permitted for on-road use. It appears the only known allowance of an electric bicycle is if it is an electric powered moped, at this time. There is a proposed bill to allow ebikes. As of May 2009, Bill A2393("Defines the term electric assisted bicycle") has been passed in the NY State Assembly and its corresponding Bill S4014, sponsored by Senator Thomas Morahan, is before the NY State Senate.
Speaking of which, if you're used to non-electric cycles, be aware that e-bikes are heavy and capped at 25kph or 15.5mph. In many cases, that means the bike starts to feel like its actively fighting against you, if you try to push the speed higher than that by pedalling. That's especially true with heavier bikes, for obvious reasons, and can take a while to get used to.
To qualify as an electric-assisted bicycle under state law they need to have a seat and fully operable pedals for human propulsion, meet federal motor vehicle safety standards, an electric motor that has a power output of not more than 1,000 watts, maximum speed of not more than 20 mph (electric motor and human power combined), disengages or ceases to function when the vehicle’s brakes are applied, two or three wheels