A group of 126 Tesla Model S P85D sedan owners in Norway have filed a lawsuit against Tesla claiming that their vehicles aren’t as powerful as the company advertises.

Bloomberg reports that the owners found that their models only put out 469 horsepower versus the staggering ~700 horsepower that Tesla pledged. As such, they’re seeking unspecified reimbursements from the electric automaker.

Tesla spokesperson Even Sandvold Roland told the publication that the vehicle meets requirements according to the measurement method required by authorities. So what exactly does that mean?

Tesla has addressed this matter in the past (and has even been sued over it). JB Straubel, chief technical officer for Tesla, explained it like this in a blog post last year:

Defining electric power in terms of horsepower is not very intuitive. Kilowatts or Megawatts are a much more useful unit. Electricity alone can't generate physical motion the way a horse or a fuel-burning engine does. An electric motor converts electricity into motion. Think of electric power as flowing much like fuel flows from a tank to an engine. Various situations (low state of charge, cold temperatures, etc.) can reduce this flow of electrons below the ultimate capability of the electric motor. In other cases, the potential flow of electricity may exceed the capability of the electric motor (warm battery, short duration accelerations, etc.). Since the battery electric horsepower rating varies it is not a precise number to use for specifying the physical capability of an EV. The motor shaft horsepower, when operating alone, is a more consistent rating. In fact, it is only this (single or combined) motor shaft horsepower rating that is legally required to be posted in the European Union.

Further complicating matters is the fact that the “D” models have dual motors – one in the front and one in the rear. Tesla used to simply take the horsepower rating of each motor and add them together to get its equivalent horsepower output which was 691 horsepower. It seems that Tesla has moved away from that method as I’m now unable to find any Model S horsepower rating on its website.

The Oslo District Court is expected to hear the case in mid-December.