If you are sure you will have that 5 cents a KWH rate on the weekend, and you are always going to do laundry on the weekend  then electric might be cheaper, but without that special rate Electric will be more expensive than natural gas.   I have a smart meter that tracks usage by the hour(I can see it on the web site) so the electric company can vary the rate by hour and by day if they want to so for me there is nothing gained by switching from natural gas to electric not even to a heat pump dryer.

I don't know.  For me I guess I don't care too much about dryer options. If it dries too hot, I will get there and remove the clothes when I think they are done regardless of what the dyer does.  The new dryer is $250.  How much did your 19 year old dryer cost?  If it was close to $250 how long do you think this new dryer will last?  I have this feeling that if the cost is close to the same the new one will not last more and a few years....this is nothing but my opinion because I think nothing new is made to last more than 7 years. 

I would do as Malcolm suggests and have the vents cleaned and the dryer serviced and see how it performed before buying a new unit.

The new guidelines?  I seem to think that the new guidelines have the dryers stopping before most people think the clothes are dry--but hey it used less energy.  I don't know why I think this, but consider that.