Visigraf.com We see what you mean.

Looking at the smallest system that would make an economic difference here at home.

My electric service is priced on tiers, with the baseline allocation at $ 0.12 /kwh. However, it turns out that I used 280 KwH that was priced at $ 0.29 or higher, some at $0.40/Kwh. When you see that this little peak was driving a big increase in the bill, it seemed logical to explore the smallest system that could make a difference. It turns out that a system that saves only 40% of the peak energy use would save %60 of the bill each month. Even more significant in winter.