While I never took the time to quantify this, as I said, I always had a sense that this was not a viable idea. In other words, my educated guess told me it would be a waste of time to even evaluate the concept.
> If you only run your equipment a few hours a day in the summer months when your excess solar power is most abundant
As a point of interest, in my region (Southern California) the point of peak efficiency is shifted into the March-April-May period. Most people assume summer is when you do best. I too made that assumption before installing my array.
There's an interplay between available solar radiation and panel temperature. As panels get hotter they become less efficient. This negative temperature coefficient is about 0.4% per degree C. Baseline specification are given for a panel operating at 25 degrees C. In the summer panels easily reach more than double that temperature. Which means that, in round numbers, you lose at least 10% of your generation capacity. A system that peaks at 10 kW in April might only yield somewhere in the 8 kW to 9 kW region in the summer.
There's also how the energy is used. In the summer we have to run the air conditioning system nearly all day. That's about 5 kW for, say, ten hours a day. The AC system is off outside of the hottest months of the year. Which means we have a lot more excess energy during that time, in fact, if the AC isn't running we could run mining equipment consuming 5 kW for about 8 to 10 hours per day and still come out net positive in terms of energy costs to the utilities.
Also as @Nbox9 mentioned, miner heat could be used for heating the home. This means that using excess energy outside of the period of the year during which air conditioning is necessary could be used for both mining and some nominal amount of heating. I can imagine a fully optimized system where you can use this to heat water and perhaps some of the home. Crazy, I know.