In the future we are likely to need to reduce our energy consumption at some point.
Considering who/how/when/&c to do this has proved the subject of some debate, which is beyond the scope of this idea. The concept I propose may, however, go some way towards maintaining the lifestyle to which we have
One area where energy is required is the heating of water, for bathing, washing clothes &c. In variable but temperate climes (like the uk) this poses a problem. The Sun can be used to effectively heat water, but this is of intermittent utility. During cold spells the water must be heated using real fuel. But there are various other sources of waste heat from which energy might be scavenged.
I propose that future buildings be designed with this aim in mind, incorporating several paths by which cold water could flow on route to the hot tank. These could include:
1) Solar waterheating panel
2) Space-heating system flue
3) utility room wall panel (behind freezer & refrigerator)
4) waste water efflux (particularly shower out-flow)
An electronic device would monitor temperature levels of the water inputs, increasing the proportion of the warmer suppliers, but not shutting colder ones down entirely, to permit
The rate at which water fed into the tank would be regulated within wider bounds than current.
Using a memory of past water supply temperatures and demand, a part-full tank might be held until warmer water became available to refill it.
This would all reduce the need to expend high-quality energy heating up more water.
If a wind-turbine is installed on the property, then sometimes it may have nothing useful to do. In the UK it isn't economically viable to supply small amounts of electricity to the grid. With just a little more electronics this energy could be used to heat up the water already in the tank.