Hi @Caban Sorry for the late reply, I have been dealing with some issues interstate. I was very lucky in that I got my PW2 Musk Stick before they shot up in price, It was about 11K, I have had it for 2 years current degradation is approx 5% which is pointing at a 75% total capacity at the 10 year mark. Comparing previous power bills and as to when it pays for itself is a little harder as I got the whole system installed once I bought my new house. But if I were to compare to my old power bills ...