I am not going to tell you how many you need but maybe I can help you to understand the math involved.
25,000 watthours divided by the number of equivalent hours of full rated output from a PV (photovoltaic) module.
In other words all of the power produced over the period of a day divided by a PV modules full rated wattage.
You can find that at this site.
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/Select; Average, Annual, and Flat Plate Tilted South at Latitude. Find your area on the map and that is what you would divided by.
I am just going to pick a number out of the "hat."
4 hours of equivalent full rated output per sunny day.
25,000 / 4 = 6,250 watt PV array and at $4.00 per watt not installed equals $25,000.
You say your paying $60. a month now for grid power?
$25,000 / $60 = 34 years of electric bills.
Of course PV can be modular, which means you do not have to install it all at one time. You could have a PV array installed with provisions of adding more to it as time goes by. It sounds as though you are thinking about a "grid interactive" system. No batteries. You could search in your area for qualified supplier/installers and maybe get a quote. Who knows you might get lucky and find one that does it all for you "turn key," including any government handouts oh!, I mean tax incentives, to help you purchase a system
On a personal note, I had greater expectations from the RE (renewable energies) industry. More so from the PV industry. It would seem, to my mind anyway that, all that has happend is, RE has jump into bed with the politician's and other energy producers, all three holding their hands out wanting more and more tax payers money. I will give them this much, RE has convinced the politician's and energy producers to use saving the planet as a selling point.
In the words of Jethro Tull, "he who made little kittens, also put snakes in the grass."