I think some of the higher end Polars like the S720i have coded transmitters so that should eliminate bogus readings. I think there's enough of an advanced descrimination circuit for them to cut through the electronic white-noise. My Shimano FlightDeck wireless (uncoded) computer can be effected by stray EMF but I literally have to be sitting on top of the source such as a traffic sensor pad at a stoplight. On my MTB which has electronically governed shocks (K2 SmartShocks) wireless is not an option because the EMF from the shaft position sending unit and the piezoelectric damping valves from the front shock play havoc with the wheel sensor so I use a wired harness. Powerlines on the other hand don't seem to effect it even when they're directly overhead. Honestly, I think you're safe buying it and then riding around your area. If you do observe a lot of sporadic readings then return it.