The problem with home-produced solar energy is, as already mentioned, that you cannot (yet) sell it back into the grid and cannot use it directly to power appliances - it has to be stored, e.g. in batteries, normally 12 volt blocks.
As most people's appliances are 220/240 volt, you will then need an inverter, which itself consumes energy. So it would obviously be better to have 12 volt appliances, but they tend to be much more expensive.
As far as running air-cons from stored energy is concerned, it's hardly a goer since the units consume anything from 1.5 to 3.5 KW/h as opposed to only around 100 watts/h for a ceiling fan.
The key here is not energy production but energy conservation.
This has to start with insulation of the entire house and passive solar measures from the outset: e.g.
1. New Cool-type roof with white reflective tiles, 21 baht each compared with 16 baht for non-reflective, so only around 10k baht more expensive for a 200 m2 home (the manufacturers claim reflective values of up to 85% and 30% reduction in air-con consumption for this measure alone).
2. Roof space ventilation is also essential, i.e. slats to allow updraft under the eaves and vents in the gables to promote air circulation.
3. Reflective insulation on top of ceiling boards.
4. Wall insulation, e.g. by creating a second skin with a cavity and/or keeping direct sunlight off walls and windows.
5. House raised above the ground approx. 90 cm to also allow air circulation from below.
6. Facing the house in the right direction, taking account of the path of the sun and prevailing breezes.
Using LED lights also reduces consumption considerably and these could then easily be run from stored solar energy.
It would be feasible to run a small solar system for lighting, fridge, computer, TV, hifi, fans and other low-consumption devices.
This could comprise, for example, 6-10 solar panels, 4 banks of 12 v batteries, an inverter, charge controller, switches and wiring.
Ball-park cost estimate for purchase and installation of such a system is around 200-250k baht.
This would obviously be very useful as a back-up system but could also be used on a permanent basis.
We are presently building such a system for ourselves, which will be used to charge our 2 electric cars, 1 electric motorbike and then our storage batteries for the in-house purposes mentioned above.