How accurate is the solar-estimate.org solar panel calculator?
The solar-estimate.org solar panel calculator is built to be usable by homeowners who do not know how much electricity they use in terms of kilowatt hours. They can generate an estimate only from the $ value of their monthly bill and their zip code.
This is the chief limitation of the calculator the fact that from very little information we make assumptions about how many kilowatt hours of electricity you use.
In most cases the solar-estimate calculator is around 80-90% accurate in terms of forecasting the number of solar panels you need and their cost. However, there are some cases where it is less accurate.
Where accuracy becomes more difficult is with forecasting avoided power costs, savings and payback periods. This requires accurate details of the specific electric rate plan you are on and also assumptions about the future rate of power price inflation that no-one can tell for sure. As most web surfers don’t know what rate plan they are on there is little point building a solar calculator that requires this information to use it.
Where a more accurate solar calculation is needed, or where time of use electric billing is in place we recommend that you use the CutMyBill solar savings calculator.
However, even with this calculator, the most accurate on the net at forecasting solar savings, it is still inherently inaccurate because it involves making an assumption about future power prices that no-one can know for sure.
When most people use the solar calculator they realize that solar offers a better return than many other investments and so are comfortable to purchase solar knowing that the exact level of savings and the exact payback period cannot be determined with 100% accurately by any software or calculator.
Most homeowners are coming to understand that while there is the 26% federal tax credit and net metering (gives a system owner retail value for excess solar energy generated during the day) the investment case for solar (while inherently uncertain) is as as good as it is going to get.