Superstorm Sandy knocked out power for more than 8 million customers in the Northeast last year, but some hospitals and universities in the region managed to keep the lights on by using their combined heat-and-power systems.

Efficiency advocates want to see Congress doing more to promote use of the technology.

Combined heat and power —also known as cogeneration — is the production of electricity and heat using one fuel source, such as natural gas or biomass.

The integrated system can provide onsite power generation and recover the waste heat to warm and cool the complex.

Companies that build and use the combined heat-and-power systems were meeting with tax-writers on Tuesday in a bid to adjust the size and capacity of systems eligible for a 10 percent investment tax credit for industrial energy efficiency. They also will target lawmakers from states that have deployed a significant amount of combined heat and power or that could benefit from cogeneration systems.

“I think up and down the East Coast, folks are going to be looking to this — looking to how New York and New Jersey can rebuild, and how they can build resilience, and what other mayors and states may do prophylactically,” said Phyllis Cuttino, director of the Pew Charitable Trusts’ clean-energy program.

President Barack Obama already has signed an executive order setting a national goal of achieving 40 gigawatts of new combined heat-and-power capacity by 2020.

The administration can also promote cogeneration by keeping it on the radar of municipalities still rebuilding from Sandy, Cuttino said.

“[Combined heat and power] may not be your first thought when thinking about resilience,” she said. “But it ought to be.”