What is the most efficient way to cool a house?

 central AC w ducts  200 ft x I I/2 ft x 6 in ducts mean more surface not accessed by sunlight,prone to catch dirt mold and bugs,,,,a window unit may be better,,along with window that are snug,raiseable or lowerable at the top to vent heat,,insulateion betw inside and outside should be up tot he job of retaining winter heat,keeping it cool in summer,and sealed from dampness

Locate it in northern Alaska not in Phoenix.

bury it or build it underground . in australia in a town called Coober Pedi they live in old mines underground , nice and cooling ad no airconditioning !!

good insulation . double glazed windows and air conditioning 

Depending on where on lives, a heat sink type system is the most efficient. Can even be run on solar circulation pump costing next to nothing in operational fee's if done properly. Of course installation would be a pretty penny. Backed up by multiple smaller independent zone systems. Again, higher installation but much more efficient to run. 

of the 3 A/C choices you describe, go with Central Air Conditioning with multi-zone thermostats.

This way, you don't have to air condition ( or heat) the entire house if you are not using certain rooms.

And, of course, pay attention to proper wall/ailing insulation and energy star windows/doors along with the proper house placement on the Iot with sufficient roof overhangs and trees that will never interfere with your roof while still providing shade.

We hada small oaktree 16' away from our house. I asked the architect if we should remove the tree and he said no. I was 27 at the time and took his word. Big mistake. That tree grew tall with branches interfering with our chimney flue, our roof and our gutters. So remember, before you know it, trees close to your house do grow and are a nightmare!

Well that depends on the type of house, ranch 2 story 

   Also the size. 

   Having trees to shade a house from the sun is a huge factor .

  Myself I have a 2 story  with a basement around 2k square feet.

    I have central air , the house was built in 1969.

   I also use a window ac unit in our bedroom upstairs so I don’t have to set the thermostat so low to cool the upstairs .   I play with my air returns by that I have trying to get the air mover to suck more air from upstairs where it is warmer . The cool air falls anyway to lower parts of the house naturally anyway .

     Not running a stove or oven or other things that generate heat in a house helps also .

   Just remember sometimes high efficiency just costs more than it’s worth .

You forgot one of the best ways. Increased wall insulation and high efficiency windows. 

oh dam, you forgot to spam your HVAC companies name into that

ha -- the 'most efficient' way is to use natural cooling -- example: heat exchanger on a closed loop water system that moves excess heat underground [where the temperature is near a constant 59 degrees]