Sounds like you are talking about a grid-intertied solar power system with a battery backup.  With grid-intertie you can buy only as much solar equipment as your budget can handle, then pull the rest of what you need from the grid.   The inverter you use for grid intertie will send extra electricity to the grid turning your meter backwards.   It's like storing your extra energy in the grid instead of in batteries. 

But with gridtie, when the grid goes down, so does your system.  So, if you have appliances you need to be able to operate at all times (computers? water pumps? lights?) you will need to ALSO install a small bank of batteries and keep them charged up.  That way, if the grid goes down, you still have juice.  This is called gridtie solar with battery backup.  Good luck!

You can also use a battery based solar system that will run a dedicated breaker sun-panel.  Make this panel bigger than you need to start with so you can expand later as your budget grows.  The if your solar system inverter is one of the newer programmable types, you can run this sub-panel's loads mainly off the the solar and program the inverter to turn on the grid AC to assist the loads and charge the batteries in times of low solar gain or high loads.  Inverters like Outbacks or new Xantrex XW models can do this automatically.

As you budget allows you can add more solar and more loads to this sub-panel until it basically runs the whole show.

Solarboy

ok, lets start off with some basic information bro. good if you can provide a budget, but if you are not comfortable with that, maybe you really should provide pictures of the exterior of your house and surrounding. questions below mainly for off-grid systems, some helpful for grid-based as well.

1) where do you live and how is the sun hours like over there?(worst case scenerio)
2) how many foul weather days do you need to prepare for?(worst case scenerio)
3) how many appliances do you have?
4) their power consumption?
5) how many hours do you need each of them a day?

if you need to use wind-power, situation gets abit complicated, so far from what i see, for wind-power to be efficient surrounding is a major concern, climate and altitude are also contributing factors.

Here's a great place to figure out or estimate sizing specs. http://www.freesunpower.com/system_sizing.php

Interesting video about how "Dave" installed his system.

I agree with "g1rock" that the extension cords are not the best way to distribute the power. Messy looking and not real safe.

If you want to build a system for yourself, something like this one, there are a couple of other areas that could use some improvements;

1) It looks like the wet-cell batteries are in the back porch area of the house. When wet cell batteries charge they give off Hydrogen gas, which is very explosive. This kind of battery needs to be vented to the outside. His charging system is small enough that he is not producing much hydrogen gas on a day-to-day basis, but when he equalizes his batteries, the off-gassing could be a problem.

2) Most folks aren't too worried about 12-volt batteries because the voltage is low enough so as not to be a shock potential. The problem is that batteries store a huge amount of energy. If something metal was to fall on the terminals of the batteries, the energy would be released very quickly and could start a fire. The batteries should be in a cabinet or box to limit this hazard.

3) Another suggestion to improve this system would be to provide appropriate fuses or breakers to protect the 12-volt wiring. As Dave says, his battery bank is rated at 440 amp/hours. If a short developed in the wiring, these batteries would be able discharge this stored energy instantly - it would overheat the wiring and set the wiring insulation on fire.