Installing solar eliminates the majority of utility expenses. There are a few reasons you might receive a power bill when you have solar installed, so this will help clarify.
1. Remember: you will continue to receive a utility billing statement from the power company.
It's important to know that you will have to pay a little bit every month to be hooked up to the grid, because of net-metering and the accompanying standard connection fees. (A solar salesperson should never, ever promise that you won't get a power bill at all, or that you'll be "100% off the grid".)
If your system is designed to cover all of your electric usage, the utility bill will include nominal fees and taxes, but will not include any charges for actual electricity consumed. If this is the bill you're talking about, it's normal and everyone else with solar still receives it too.
2. Your consumption may have increased recently.
Your solar is designed to produce a specific amount of energy. Systems are generally designed based on your historic usage. For example, if your home uses about 10,000 kWh per year, and the solar system is designed to produce 10,000 kWh, you wouldn't be charged for electricity. However, if you increase your usage to 15,000 kWh next year, you will be charged for the excess. The solar can't start producing extra power "just because". (Solar might seem like magic for how quickly and easily it eliminates your power bill, but it's more Star Trek than Lord of the Rings.)
This can happen without you realizing it. For example, your AC might be running longer if you're staying at home more often during the day. Certain appliances can be "vampires" and draw energy even when powered off. There are plenty of ways to conserve energy and reduce consumption, and it's up to individual homeowners to explore what will work best for them.
3. Your solar may have an issue.
Lastly, your solar may be experiencing some trouble. Solar panels are extremely durable and stable devices, but they are electronics, and can't ever be guaranteed 100% perfect right out of the box. Inverters can experience errors, outages, or failures as well. Every solar array is equipped with a monitoring system that allows users to identify problems in real-time.
If your system ever reports a production error, let us know right away and we can get to the root cause. The good news is that problems are rare and warranty coverage lasts a long time.