Tankless and recapture and solar oh my...

I am getting way ahead of myself here project wise, but it's always fun to plan out the future ;) I have recently moved into a house that has a crawlspace into which I could fit a shower drain heat recapture device. I am excited about this for the relative ease of install here (previous house was on a slab with showers on first floor, not going to happen)! That will reduce costs for hot water for showering, but wont help with the fact that the hot water heater we've got can barely fill the tub if you happened to be washing dishes at the same time. To increase that comfort I'm thinking that a tankless might be the first big purchase but can the 2 work well together? If my water input to the tankless is pre-warmed by the recapture it will throttle back and keep heating right? Or if I send the warmed water up through the cold to the shower will I mix in less and less of the hot water until the demand is too little and it shuts off? Do the newer ones handle varied loads well?



Then in the far distant future I want to capture some of the huge amount of solar energy that falls on the roof just a few feet from where the current water heater is in the attic. but that will need a storage tank. Should I keep the current water heater tank in line before the tankless heater and run the solar loop through that? So that whatever temperature is in the tank the tankless heater will add only enough to bring it up to the set temp until it runs out? Or is that asking too much from the control systems of these devices.



I understand these are vague desires at this point, but I dont want to lock myself out of doing the recapture or the solar in the future by purchasing the wrong tankless now.



Thanks for listening to me wax poetic about future projects!



This is a great site :)