100 W. 57TH STREET

What's with ground leases so much in the news lately? In our second item about them in a week, a consortium is paying $285 million for the land beneath Carnegie House, the 324-unit co-op at 100 West 57th Street. Since ground-lease rents are typically 6 percent of current market value, reports The Real Deal, rising New York real estate prices means the current $4.4 million rent the cooperative pays annually would be $27 million if the rent were to be reset today — so what's it going to be in 10 years, when the rent is scheduled to be reset? Which brings to mind a variation on the old joke: How do you get to Carnegie House? By having enough money to make ground-lease payments the size of Montana.

The Carnegie House, at 100 West 57th Street, is a fairly traditional co-op. Complicated in 1962, the grey-brick beauty was named after nothing less than Carnegie Hall. Yet even such an old-school cooperative wants to keep up with the times, and if it can lower its electricity bills by 15 percent, so much the better. Thus, the more than 300-unit, 21-story building did a top-to-bottom overhaul of its energy systems — a $788,000 project that will recoup its cost in six years, thanks to $197,000 in incentives from the New York State Energy Research and Development Authority (NYSERDA), a loan at about half the market rate and the aforesaid electric-bill savings. Amy Zimmer of DNAInfo.com covers the Carnegie and other buildings, and offers five energy-savings tips.

The 250-unit Normandy, located at 140 Riverside Drive on Manhattan's Upper West Side, recently phased out its old-style bulbs. For co-op board president Bennett Lincoff, convincing the other board members it was a good idea was easier than screwing in a light bulb. The fact is, according to energy experts and building managers, if you still have incandescent lighting in your building's public spaces, rather than compact fluorescent light bulbs (CFLs) or light-emitting diodes (LEDs), you're probably wasting money.