Alright, lets get started.
Last year, Ronnie's utility expenses were = 1935.67 $
After switching to electric water heater to solar water heater, his yearly utility bills get reduced.
This year, Ronnie's utility expenses are = 862.40 $
So the difference on utility bills Ronnie saved =
so, difference Ronnie saved = 1073.27 $
So, the percentage of amount Ronnie saved =
Percentage of amount Ronnie saved = 55.45 %
Hence, 55.45 % Ronnie save on his utlility bills by switching to a solar water heater. : Answer
Hope it will help :)