Ummm..
Try a controller with a digital readout, and check your Amps and watts that the panels are actually producing. Or, at least test the power that is actually being fed into the batteries with a basic ammeter.
A panel rated at 100W... may not produce 100 watts / hr for 5 hrs / day.... And, you may need to adjust angles and have a solar tracker if you want to maximize power production.
On the bright side...
Add your basic Power Feed Connect Fee to the "basic equation" ($10 to $20 / month even if you don't buy any power) so your savings are a bit higher.
Also, some utilities charge if you have to extend their wires. I.E. Not paying the fees to extend power to your house might pay a portion of the cost of the system.
An additional consideration....
You may be "leaner, meaner, and more efficient" when running by solar... Say, you cut your power consumption by a factor of 10... So, if you generate 6 cents of solar power, if you had a "power feed", you would likely have bought 60 cents of power.
Of course, if you generate 1500 watts, and you only use 500 watts, then you really can't say that you generated 9 cents worth of power when you "wasted" 2/3 of it.