For solar:
Electricity - Remember to have one thick, large in Diameter, pipe leading From the roof down till your electricity Boxes Which are to be in One Straight Line.
Geyser - Get the household water tank placed on the highest Roof and not Just the upper Floor's like you said there'll be One room only on the upper story so the water tank ought to be on top ov that.
Also, try to save piping by Having at least the upper Floor's and at least one, if not more, ov the ground Floor's bathrooms/kitchen in a single Line. The conventional geyser you will get now is to be in the Same Line i.e. Water tank - bathrooms/kitchen - geyser. This saves extra piping cost and one is more thankful when getting solar geyser because the Length ov pipes Required then is Lesser and Thus saves Money.
You have not mentioned solarizing your house but Just in case Later on you do plan to, the above tips will help avoid Drilling in walls for wires and save extra Expense ov additional Commodities Required for geyser.
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