The least energy-consuming way to fly

Question

Do it yourself

Good day to all.
The essence of the question is in the title.
Analogues of ordinary aircraft (aeromodelling), various multicopters, helicopters, some kind of hybrid schemes based on these bases come to mind. It is understood that this should be a DIY device, small in size and weight. There is no need to carry any cargo, except perhaps the necessary equipment and a body of 200-400 (?) grams, excluding batteries.
The answer to the question is not at all visible to me - what is the least energy-consuming method? or...
What type of flying device can last the longest in flight?
upd
Preferably managed. Within the planet and atmosphere.

Answer 1

What type of aircraft can last the longest in flight?

CEP suggests - a balloon.

Answer 2

It depends on how you calculate energy costs. If in J * Km, then this is definitely a satellite. A lot of energy to put into orbit, and then flies for a long time and "practically" without energy consumption.

Answer 3

It is necessary to determine what energy costs are being discussed. Only during the flight itself or for the creation of an aircraft and flight support?