I’ve been tracking the temperature in my house and roof space for quite sometime now. My house is mostly single level with hot water cylinder in a moderate sized cupboard in center of the house. I notice the temperature in my roof space on some on these hotter summer days peaking between 40-58 degrees Celsius.

I was thinking whether that heat would be better used if I had a small DC fan that drew that hot air into the hot water cupboard (to supplement the cylinder by reducing heat loss). I get that a typical HWC internal water temp is around 60 degrees and they are pretty well insulated, so there is zero chance of it *maintaining* water temp, but being the ambient temp of the cupboard itself is likely a good 15-20 degrees lower than that of the roof, would drawing the hotter air help minimize the on/off state of the cylinder helping reduce power? The distance from ceiling to top of cylinder in cupboard is about a meter, and obviously only a sheet of gib board apart. A low wattage DC fan (like a PC power supply fan) would mean low power consumption. I still need to wrap the cylinder and I get this is more efficient than the above solution, but would combining both be worthwhile doing? Any downsides? Waste of time?

An ESP WiFi chip would do the temp comparison and only run the fan should the roof cavity temp be high enough.

I’m trying to think of every little power saving idea, obviously it started with LED lights, heated towel rail timers etc, but I figure all the other little things also add up, and it’s also an excuse for a new project...however I don’t want to waste my time with this if the difference will be negligible.

Thoughts?