If you are in the highest tier and get a 5KW system it should save you about $2K a year. I think it costs about $25-27K to install such a system, so 26/2 = 13 years for the average person whose bill exceeds $150 on average. Though we have a new roof it is an older house so the pitch isn’t very steep. I would love to buy a system but the wife doesn’t want to incur any more debt and I can also see that viewpoint. So in a nutshell if you live east of the 5, are not planning on replacing roof soon then I think it makes since if you fall in the tier 3/4 arena each month.