If you have an old bill from when the electric company supplied ALL your power the solar HW pre-heater saves about 10% (I assume it’s a pre-heater and you still have the regular HW heater. AW full duty solar HW heater would save about 15%). It would be a greater proportion after installing the panels of course.
I’m curious what the payback period is for the solar HW heater including installation
Now we haven't had everything in place for a year so we're waiting for a full year of everything. That will happen next Jan because this past Jan they did the PV installation.
Duke electric bills are a nightmare to try to read and interpret so it is hard to say what portions of the whole system have contributed what to the drop. If I had done it one year at a time, AC first, then a year later HW, then a year PV I probably would have been able to see what each part contributed to the overall bill.
Overall I did a rough calculation that based on the drop in the bill and the rebates it will break even between 7 and 8 years unless Duke increases rates (which I'm sure isn't likely <'/s>).
Finally, I believe that the subsidies prop up the manufacturers' prices and if they stopped the subsidies the prices would drop correspondingly because the greenies have installed what they are going to install and the rest of us wont install them if they are too costly. I only did it because I had the money and moving closer to retirement and watching the elec market in FL I believed that the payback pd was reasonable and I wanted to get rid of a monthly payment that was only increasing.