There are a lot of clunky old pool heaters on the market, and a major utility company wants homeowners to upgrade.

SoCal Gas, the nation’s largest natural gas utility, is offering $300 rebates on natural gas pool heaters that have a thermal efficiency of at least 84%. The utility offers an even more generous kickback of $750 for so called ultra-efficient heaters, which boast an efficiency rating of 94% and higher.

A caveat: Rebates only apply when homeowners replace existing heaters with one of the more than three dozen qualifying models. Folks who didn’t previously own a heater do not qualify.

SoCal Gas, which supplies energy to 22 million consumers, anticipates issuing about 5,000 residential pool-heater rebates this year. “Our research indicates the majority of existing natural gas pool heaters in use range between 78- to 82% thermal efficiency,” said Melissa Bailey, SoCal Gas spokesperson.

The advent of ultra-efficient heaters prompted the utility to explore the incentives, Bailey said.

The move evoked mixed reaction from the industry. One manufacturer of several units that qualify for the program is disappointed that rebates only apply to residential heaters. Commercial swimming pools, which tend to be heated around the clock, would benefit even more, said John Kane, national pool sales manager with Raypak. He also expressed doubts that the program would do much to move the needle in terms of residential sales. “Those heaters are pretty expensive, and your average homeowner isn’t going to be swayed,” he said.

Others think the rebates will stimulate the market, just as incentives for variable-speed pumps proved an effective carrot.

“I think the really rich people are buying those heaters,” said Phil Gelhaus, chairman of the board at the Foundation for Pool & Spa Industry Education in Sacramento. “That particular person heating their pool year-round is going to have a major payback.”