I use the the Aeon Home Energy Meter for this. I have one clamp on the dryer and one on washer. Unfortunately I don’t think they are available new any more(???). Some on ebay but little pricey… https://www.ebay.com/sch/i.html?_from=R40&_nkw=aeon+home+energy&_sacat=0&rt=nc&LH_BIN=1
Try this SmartApp with the multipurpose sensor.
It was originally in the SmartThings public repo, but I have added recently some announcement feature.
I hope this would work for you.
I installed it and am giving it a try! I’ll let you know! Looks like it will already be better than the , “wait 5 minutes” rule I’ve instituted using sharptools.io