Turns out, they're not good for the environment, according to some experts, and could be phased out as Europe toughens the rules.
Draft green finance regulations would ban carmakers from labelling plug-in hybrids, or PHEVs, 'sustainable investments' from 2025, which could put investors off.
More planned rules on emissions of pollutants such as nitrogen oxides could at the same time push up the cost of producing the cars, which contain both an engine and a battery.
Until now, EU policy has put PHEVs on a par with all-electric cars, which helped spur tens of billions of euros' investment in the technology.
But environmental experts are pushing Europe to strip the hybrid of its green credentials.
European NGO Transport and Environment says they're heavier than conventional cars and so use more fuel.
A clean transportation report last year said hybrids' fuel consumption and CO2 emissions are up to four times the level they're approved for, because people don't charge them often enough.
Some carmakers expected to sell plug-in hybrids until at least the end of the decade as a bridge to fully electric, but now look to be shifting away - as the changing rules make them harder to sell.
BMW and Renault, which have not set a date for going all-electric, are among the companies firmly in the hybrids camp.
Which argues the charging infrastructure still isn't there to support the shift to electric - so hybrids are still popular for consumers who want to drive greener.
Volvo, meanwhile aims to be all-electric by 2030. Its CEO told Reuters that made it more credible as it pushes the EU to make improvements to the charging network.
