They don’t look the part. The Beresford and the El Dorado, two prewar jewels on Central Park West designed by the famed architect Emery Roth, look more like grandes dames than forward-thinking energy pioneers. But don’t be fooled by these buildings’ regal appearances. After installing energy-saving LED lights, cogen power plants and other upgrades, the Beresford and the El Dorado are now taking the ultimate step into energy-efficiency: they’re installing battery energy-storage systems, known as BESS, cutting-edge technology that will help them shave a big chunk off their electricity bills.

For these two storied old co-ops, new is good, and the future is now.

“The driver for all this is that we wanted to create a way for co-ops and condos to be able to reduce their predominantly set energy costs,” says Alex Kalajian, chief operating officer and co-founder of the Solstice Residential Group, which manages both buildings. “The only way you can really attack that is by not accepting the traditional answers about energy: ‘It’s a prewar building, it’s a steam-heat building, there’s not much you can do.’ We just kept hearing these mundane responses.”

And the co-op boards at the 183-unit Beresford and the 203-unit El Dorado, to their credit, rejected those tired old excuses. Instead, they have embraced technology that has already sliced costs widely regarded as “fixed.” John M. Phufas, president of the Beresford’s board, estimates that the steps the two co-ops are taking will ultimately reduce energy costs by a significant amount – “from 10 percent [of the budget] to under 5 percent.”

Cathy Klema, the El Dorado’s board president, adds, “Very sound business fundamentals support these initiatives. We want to do the right thing in terms of environmental sustainability while driving energy costs down. The goal is not just to do good for the sake of doing good but to derive discernible financial benefit from doing so. As you drive down energy costs over a period of time, you’re going recover the cost of the investment you made.”

Those sound business fundamentals have saved millions of dollars over the past decade. The latest upgrades, including LED lighting and cogen systems, have added to the savings: $175,000 a year at the Beresford and $375,000 at the El Dorado. And those numbers are about to get much, much bigger.

Nearly 10 years ago, the Beresford switched from using No. 6 fuel oil to natural gas. That alone, says Phufas, a corporate and tax attorney, has saved millions of dollars in heating costs over the years. The El Dorado, whose landmarked exterior had undergone a particularly expensive window-replacement project late last decade, converted from oil to gas around 2014.

A year or two later, both co-ops installed gas-fired cogen units to generate some of the buildings’ electricity and produce heat for hot water. The Beresford’s unit has a payback time of three years. “The base cost was around $550,000, but the net cost was around $320,000,” Phufas says. The contracts required Aegis Energy, the manufacturer, to also act as the contractor and take on the risk of obtaining the incentive from the New York State Energy Research and Development Authority.

“You don’t want to be in the position where it’s, ‘Sorry, you paid half a million, but you didn’t do this one little technical thing and you’re not entitled to the incentive,’” Phufas says.

After both co-ops had installed cogen, the boards took an innovative next step: trigeneration. “Trigen means taking an absorption chiller” – a refrigeration unit that converts heat from the cogen unit into energy that drives a cooling system – “and installing a second cogen unit,” says Kalajian, the property manager. The result is free air-conditioning after payback on the initial investment.

Upfront costs for the second cogen unit and the absorption chiller were high, however – $1 million, before incentives, says William Zoha, president of Prescient Energy, a consultant hired by both co-ops. The Beresford went into contract for trigen in February and expects to have it operating by late 2019. The El Dorado is in the process of installing it, with testing to follow before full implementation.

Coming Monday: the next step, adding a battery energy-storage system