Hey Maxx, you answers here are basically correct. If you have grid power, it is generally more economical to to a "grid tie" system. In this system, the panels deliver whatever power they can to a grid tie inverter, which synchronizes with the grids frequency, and simply dumps all available solar power into your homes electrical system. It doesn't know if it is going to your refrigerator, or your neighbors, but it doesn't matter. Your electric meter simply runs backwards when you have good sun and low usage, and forwards at night, and at the end of the month you pay the difference. There are details, such as what happens at the end of the month, or year if you still have an overage, are you allowed to carry extra to the next month, and so on. One thing to keep in mind is with a grid tie system, if the grid goes down, so does your solar array. So if the power is out after a storm and the sun comes out, you still have no power, even if your array is in good sun. That type of inverter needs an incoming signal to tie to.
A "stand alone" system is like a remote cabin with no grid power, or a boat, RV or camping trailer. In this case you have to have a battery. The best bang for the dollar on this type of system is the golf cart battery. We've been doing this for 17 years, the Trojan T-105 are my favorite, good longevity and quality hardware. Any golf cart place sells these for around $100 each. With a stand alone, you have panels that charge batteries all day, then at night you can draw off the batteries for lights, small electronics, TV, cell phone charging and such. Then the next day the panel recharges the battery again. Our cabin has a small 12 volt system with a single 120 watt panel, 20 amp charge controller and two T-105 batteries, (you need them in pairs because they are 6 volts each). We run LED light strips in the kitchen and living room, LED reading lights in the bedroom and den, LED trail lights in the garden, cell phone chargers, mp3 speakers and a portable car DVD player. That panel is more power then we need for all of this. If you are going to start running appliances, like even a small refrigerator, then your array requirements go up quickly, maybe 500 to 1000 watts.
There is a third type of system, where you have batteries for backup, and a particular type of inverter that can grid tie, or operate alone if need be. As long as your batteries have sufficient power, your home continues to have power regardless of the grid. We have this ar our home, our inverter is a Xantrex "utility interactive" type, but they are sometimes called hybrid, or battery back up. This is the most expensive arrangement, but then our home has not been without power for even a minute the last 17 years, hard to put a price on that. That Tesla Powerwall is interesting, but looking at the specs, I can promise you that you can store the same 10 Kwh of power in a wood cabinet in the basement for 1/10th the cost. T-105 batteries cost around $100 each, and each holds roughly 1.25 Kwh of power. Eight of them would equate to the storage capacity of the power wall. Granted Teslas batteries perform better, discharging faster and deeper, and charging up faster if need be, but a solar array can't accelerate beyond its design parameters, what good is a battery that can under those circumstances.
Check out some sources below, and be careful getting renewable energy info on open forums like this. I'm always amazed how many people will impart their expertise on solar power, who have never laid a hand on a panel or inverter. Take care Maxx, Rudydoo
I don’t see that ever paying off after reading about bitcoin mining. Take out your current electric bill, see what the total charges are including taxes, divide it by your “usage,” in kWh. This is your total cost per kWh. Most sites I looked at say if you’re paying over 7 cents you won’t get ahead. Making solar power costs more than this.
homepower.com MREA.ORG Trojan.com The Complete Battery Book, by Richard Perez, library