What is the total approximate surface area of solar cells required to generate 20 kwh per day...?

Question

In Summer in Central Texas?

Answer 1

Here is a start.

Answer 2

With incident radiation of 1 kw / sq metre, and 10% efficiency in capture, and 8 hours a day capturing, we get 800 watt hours per day per sq meter of panel.

Those numbers are deliberately vague, because you need to specify what your average incident radiation, your percentage of capture are expected to be... based on location and specific panels But these numbers are close to the average actually observed for a well designed array.

If different parts of an array are in different levels of incident light and you are wiring them in series., you have to use the lower level for the whole array, not the average.

If the different parts in different light are wired in parallel, one uses the average wattage.

In Texas you would have to plan to dump excess heat if you do not have a good use for it. About 85 to 92% of the sun's rays will be absorbed as unwanted heat.