As @jlj.pers suggests, I would go for the Smart Plug if you can because you’ll get reliable detection and notifications. That said, be careful you don’t overload the plug. I’m using a Wemo Insight on a combined 120V washer/dryer which peaks at 1200W.
In theory you could play with the Goals notifications and use those but that’s only an ugly partial solution at best. There’s not a lot you can do with the Device notifications in this situation other than perhaps asking Support about the specifics of the detection algorithm and whether it could be persuaded toward perfection.
Without (hopefully!?) sounding like a Sense evangelist I’d suggest getting ANOTHER Sense and dedicate it to your washer & dryer circuits OR add a Solar CT to your existing Sense (assuming you aren’t using it for Solar) and put those CTs on the washer/dryer circuits if either are high current (and/or over 120V). I’m using a second Sense on my Hot Water tank (Main CTs) and AC (Solar CTs). Works like an ironic charm and doesn’t interfere with my overall panel data.
There has been plenty of discussion on this and suggestions from others.