James Dyson, of bagless vacuum cleaner fame, has accused German rival Bosch and Siemens of cheating on official EU energy efficiency testing. Dyson claims that its competitor's 750W vacuums draw only 750W when they're being tested in the lab, but there's "control electronics" that up-rate the motor to 1600W when they're actually being used at home to suck up dirt. The best bit, though, is that Bosch is also involved in the Volkswagen emissions scandal: Bosch wrote the "defeat device" code that was ultimately used to cheat on emissions tests around the world.

Dyson, the company, today filed legal challenges against Bosch in the Netherlands and France, and against Siemens in Belgium. (Bosch and Siemens, or BSH Hausgeräte, is actually just one company.) The vacuum cleaners being targeted by Dyson are the Siemens Q8.0 and Bosch GL80/In’Genius ProPerform models. Both of these vacuums are advertised as having an "AAAA" EU energy efficiency rating—a rating, according to Dyson, that can only be achieved in laboratory testing.

Dyson, the man, said: “Bosch has installed control electronics into some of its machines to wrongfully increase energy consumption when in use—to cheat the EU energy label. Their behaviour is akin to that seen in the Volkswagen scandal. It seems that industry is rife with manufacturers engineering to find their way around tests, rather than engineering better, more efficient technology. This behaviour is seriously misleading customers.”

Bosch, for its part, "strenuously rejects" Dyson's allegations. “We do not understand these assertions by Dyson and we strenuously reject them," the company said. "We are committed to providing full disclosure on the energy ratings and broader performance of our vacuum cleaners so that consumers can make an informed decision. For reasons we fail to understand, this is not something that Dyson choose to do."

As far as Dyson the company is concerned, the main problem is that the EU testing procedure isn't representative of real-world use. For vacuum efficiency, EU regulations stipulate that the vacuum only has to be tested with an empty bag—and so that's exactly what Bosch and Siemens does, according to Dyson. The problem is, when the bag is full of dirt—which it often is, during real-world usage—the vacuum needs to suck much harder to achieve the same cleaning power. According to Dyson, the Bosch and Siemens vacuums are scaling all the way up from 750W to 1600W when they detect that there's dirt in the bag, reducing the real-world efficiency rating from AAAA to an E or an F.

Dyson, which has been riding its bagless vacuum steed for decades, obviously has a rather big horse in this race. Dyson has previously called for a new EU vacuum testing regime that takes into account real-world usage, presumably because it would bestow its vacuum cleaners with higher efficiency ratings than its competitors'. Dyson is no stranger to legal action, either, to safeguard its suction supremacy: back in 2012, Dyson sued Bosch for allegedly paying an ex-Dyson engineer for some trade secrets.