October 20, 2026 - Should Plug-In Hybrids Have Smaller Gas Tanks

This is the Telemetry Transportation Daily for October 20, 2026, and I'm Sam Abuelsamid, Vice President of Market Research for Telemetry. 

At first glance, the plug-in hybrid electric vehicle (PHEV) seems like a great bridge for people who like the idea of going electric but aren’t quite ready to go all-in. PHEVs offer enough electric-only driving range to cover most people’s daily needs, then keep going as a regular hybrid until the gas tank runs dry. The problem is: What if someone buys a PHEV but doesn’t actually plug it in? The European organization Transport & Environment (T&E) wants to fix that by limiting the gas tank size. 

Many argue that a PHEV is actually the worst of both worlds: carrying both electrification and internal combustion engines. Hybrids are primarily driven by an engine, but they add one or more electric motor-generator units (MGUs) and a small battery to improve overall fuel efficiency. The MGU helps move the vehicle by taking over some of the ICE's workload, so it doesn’t burn as much fuel. Since there's no plug, the battery (typically about 1 to 1.5 kWh) is mostly charged through regenerative braking. 

A PHEV takes the same concept and adds a larger battery (typically 15 to 30+ kWh), plus a plug so you can charge it while the car is idle and go 20 to 50 miles on a charge and then continue as a conventional hybrid. Unfortunately, many people bought PHEVs because of incentives that make them more affordable or save them money in other ways. But some surveys have found that as many as 90 percent never actually charged them. If you don't charge a PHEV, you end up dragging around 500 pounds or more of dead weight, making efficiency worse.

T&E is advocating that regulators cap fuel tanks at about 4 U.S. gallons. That would limit the hybrid range of something like the RAV4 or Tucson to a little more than 120 miles. The organization also recommends that PHEVs have at least 124 miles of electric range. For those who do charge daily but want that extra range capability for occasional trips, this solution eliminates much of the utility of a PHEV. 

A better solution might be additional training for dealership staff, so customers understand they should only buy a PHEV if they have somewhere to plug it in every day. If they don’t, salespeople should steer them toward a hybrid. 

Regulating fuel tank size is probably the wrong fix. Better consumer education, on the other hand, could work to help people find the electrification path that's right for them.

Thanks for listening.