Solar panels are rated for their maximum power output. This is the amount of power the panel can produce in ideal conditions. Idea as in right on the equator, at high noon, cool day with no smog.
Many years ago I had a old motorhome that I used to travel to events with. I used to do photography and video coverage of off-road racing events. The generator was giving me trouble, was noisy and put out enough CO to trigger the CO alarm. I removed the generator and installed two 110 watt solar panels on the roof. The panels were connected to a solar charge controller that recharged 4 golf cart batteries. This setup normally provided more than enough power for everything I needed. In using it, I learned a lot about solar power and efficiency.
Theoretically I should have been able to produce 220 watts of total power or about 18.3 amps at 12 volts. My panels were mounted flat and not angled to the sun, I had some loss of power from the battery charge controller and other factors that limited the total power. At peak day, I was usually able to produce around 15 amps. At sunrise each day, you could see the power start coming in as soon as the sunlight hit the panels. At first it was very little power but after an hour or two it would get up to near full power on a clear day. On overcast days total power generation was 1/3 to 1/4 of a normal clear day.
Overall I was able to produce enough power with this system to run the lights, small TV in the evening, laptop computer and even a few minutes of running the microwave oven each day. Most of the time, especially in the summer, I produced more power than I needed each day. In the winter time, I made less power but was always able to make enough power to get me through the 3-4 days that I was on site.
With solar system installed on a home you want to do what is called net metering. That is you produce lots of power during the day and push it back into the electrical grid. Then at night or when conditions are poor for making solar power then you draw power back out of the grid. This eliminates the need to maintain and replace a battery system. The power company takes how much power you use each month and subtracts the amount of power you gave them to arrive at your monthly bill.
The size of the system you need to power a home depends on location, weather, size of the home and many other factors. My parents have a small home in the Bay Area (California) and are able to generate all the electrical power they need for their home and their electric car with a 2.8KW (2,800 watt max output ) system. We recently checked into a solar system for our home and found that we would need a 4.0KW system to provide all of the power we are currently using (larger home and due to triple digit temps in the summer we use air conditioning). The cost quote was $20K for the system installed or put another way about $5 per watt. We have decided to wait till our home is paid off before installing solar but do plan to do it. Yes, it is a lot of money but you are talking about a system that will produce all the electrical power you need for 20-30 years with far less pollution and carbon than would result from nuclear, gas, or coal power.
Commercial solar systems are a little more cost effective to install, there are some economies of scale that help with a large system.