Be realistic about the costs of having a solar energy system. If you're paying much less than other systems that are around the same size as yours, you may have poor equipment or installation work. Like with many things in life you get what you pay for. Quality installation work and equipment isn't going to be cheap. You may have substantial savings by going with a large company, but other companies may be cutting corners to keep costs down.
Once your solar panels are installed, you need to keep track of how much power you are producing and using on a daily basis. Invest in a quality monitoring system and look at the data as often as possible. If you notice your panels are not producing as much energy as usual, it might be time to clean them.
Peter & Mary are going Solar.