Out of Spec Reviews conducted a real-world test comparing a Rivian R2 Performance and a Tesla Model Y Performance on the same roads on the same afternoon, finding that the Rivian consumed 18% to 26% more energy at every speed tested. This discrepancy comes despite both vehicles carrying identical EPA efficiency ratings.

The Rivian R2 Performance has an EPA efficiency of 105 MPGe combined (32 kWh per 100 miles), matching the Tesla Model Y Performance. Rivian CEO RJ Scaringe has stated that the R2 is 'as efficient on a Wh per mile or miles per Wh basis.'

The Rivian R2 wins the EPA city cycle with 114 MPGe against the Model Y's 111, but the Tesla wins the highway cycle with 100 MPGe against the R2's 96. The R2 has an EPA range of 330 miles, while the Model Y has 306 miles. However, the R2 weighs roughly 800 lbs more than the Model Y.

Kyle Conner of Out of Spec Reviews believes the discrepancy may stem from different EPA test paths. The EPA offers manufacturers multiple paths to efficiency labels, including a cheap method using a 0.7 multiplier for AC charging losses, which most EVs use. The more expensive multi-cycle test measures cold-weather, hot-weather, and high-speed behavior directly. Conner suspects Rivian ran the R2 through the full multi-cycle test while Tesla submitted derived numbers, though he noted on camera that he cannot certify this claim. Per-vehicle test paths are not publicly accessible.

Additional factors complicate the comparison. The EPA's kWh/100 miles figure is measured at the wall and includes charging losses, while Out of Spec measured energy leaving the battery. Backing out charging losses, EPA suggests the R2 achieves about 3.75 miles per kWh from the pack and the Model Y about 3.64. In real-world testing, however, the R2 was 18% to 26% less efficient than the Model Y. Both vehicles' odometers disagreed by about 1.7%, and the 70 mph test leg was compromised by heavy traffic on I-95 at 5 p.m.

In a 20-minute stop-and-go city simulation, the Model Y used 1.6 kWh and the R2 used 1.9 kWh—about 19% worse for the R2. The Rivian R2 decouples its front motor with a clutch, allowing it to spin one drive unit at low speeds, while the Tesla Model Y's front induction motor keeps turning, incurring windage and gear-train losses.

Out of Spec also ran a 10% Challenge: charge from 10% state of charge for 15 minutes, then drive at 80 mph until returning to 10%. The Rivian R2 held a flat 600 amps from the charger, peaking around 229 kW, limited by the charger rather than the battery up to 32% SoC. The R2 added 48.3 kWh in 15 minutes, with an average of 193 kW, going from 10% to 59% SoC. The Rivian R2 can request up to 630 amps. For a 400-volt architecture, the R2's charging performance is about as good as it currently gets.

After charging, the R2 drove 92.8 miles at 2.2 mi/kWh. The Model Y Performance, run two days earlier, drove roughly 103 miles at 3.3 mi/kWh on less energy.