That's a good idea, but can I get usage over time, IE, pump is ON at 5-6pm, and off 6-9pm? I'd like to look at when things run and experiment with disabling things based on time of day. I think my PLC can do this over the RS232 port to a PC, but not sure.

Not a fan of gadgets as a contractor vs the engineer's perspective (ain't broke, not enough features). But if you insist on this set-up I think you have to circulate water between tanks (or around house) to take advantage of least expensive source of DHW.
DSH (most upstream) tank (by the way 125* max on tranquility) feeds 100 gal solar fired, feeds electric storage which circulates back to DSH tank. DSH will run when temp is below 125, electric tank won't run when temps are above set point. This will ensure that mama is never limited to 40 or 50 gallons of hot water for the tub.
Of course I'm speaking within the confines of code which would have your water peak at around 125*.
You take it from there.
This should appeal to most engineers as your hot water will no longer be created by that simple, small foot-printed, low maintenance storage tank. Oh no.....now we can make it with a room and roof-ful of appliances tethered together in Frankenstien like fashion (resembling one of my kid's designs in the game Mouse Trap) with sensors and lights and a mother board....and relays.....and....oh look a shiney;).
j

You left out BLINKING lights.

Something displaying status codes in hexadecimal is a desirable addition as well.

:)
Thanks for taking that in the spirit it was offered.

Blinky lights are so 70's.... try a touchscreen.... :) Thanks guys.

I'm nearly as immune to engineer jokes as lawyers are to their jokes.

When the system owner gets on it with a PLC and a PC via RS 232 the thing is a science experiment that may, by some passing conincidence, also heat or cool a home...fun to watch but way off the main stream.

When I'm backed into a corner and forced to actually DO my day job, it often involves PLCs or similar contraptions and PCs, so I wouldn't want to come home to one.

engineer - I hear you. I rarely play with plcs, actually design engines for a living. Its an interesting diversion, and the setup was a good deal cheaper than regular tekmar type stuff. We've got enough going on that it would've been quite a few controllers on the wall.
Besides, I live for a challenge....