The cost of solar systems has steadily declined through the years, and with the advance of technology and improvements in production techniques, it is reasonable to assume this trend will continue.
As installation costs of the systems drop, more systems will be installed, driving costs down with volume production.
If your PV solar system is sized appropriately, you will not be generating more energy than you typically consume annually.
If you produce surplus energy on a grid-connected system you will feed it into the utility's grid and you will use that energy after the sun goes down at the same rate that it was metered to the grid.
In all 50 states, the utility does "bank" the energy that is produced and that energy is later consumed at night or in the future.
Excess energy goes out on the grid and comes back in at the same price, thus the term "net-metering".
The energy is measured by using a bi-directional utility meter.
You could try to imagine the old analog meters spinning backwards as you produced more energy than you are consuming.
This makes Net-Metering a very fair deal for consumers installing distributed generation plants.
At the end of the year, any surplus energy that you have produced is purchased by the utility at the avoided cost which is basically the same rate they pay from other energy producers.
It would not be fair to force someone (the utility) to pay more for your energy than they can buy it for elsewhere.
Some new meters may have the ability to know when the power is stored on the grid and also later used by the customer.
This is called time-of-use utility metering and rate payment.
It is very common with solar installations and specially great for charging Electric Vehicles - you get credit during peak times at high rates, then get charged for usage during off-peak times at low rates.
Actually the surplus energy you produce in a net-metered situation is not stored by the utility company but when thinking in terms of net billing, the grid acts like energy storage, although it is strictly an accounting technique and not really storage.
The energy you put on the grid is simply used to maintain the "pressure" of the feeder line you are on.
You are basically sharing your surplus energy with others (your neighbors) who are on the same feeder line as you.
In other words, if your feeder line has a net production of energy, then the surplus energy is available even further than your feeder line.
The bottom line is that your energy produced offsets the need for utility generation.
We can think of the hydro lines as pressurized water hoses.
There are three hoses in which the pressure rises and falls.
This rise and fall in pressure is 120 degrees out of phase between each line (i.
e.
as one line is at full pressure the second line is at half pressure and the third line is at zero pressure).
You get power by connecting across two lines and using the pressure difference to power whatever you plug in.
So if you plug in a heater the pressure difference is converted into heat.
If you plug in a motor the pressure difference is converted into motion.
In each case the water doesn't leave the hose and just loses some of the pressure difference between the two lines.
This analogy isn't 100% accurate but it helps to understand how your home energy would be used.