Off-grid systems are great for customers who can't easily connect to the grid. This may be because of geographical location or high cost of bringing in the power supply. In most cases, it doesn't make much sense for a person connected to the grid to completely disconnect and do an off-grid system.
Because the system is your only source of power, many off-grid systems contain multiple charging sources such as solar, wind and generator. You have to consider weather and year round conditions when designing the system. If your solar panels are covered in snow, you need to have another way to keep your batteries charged up. You also will most likely want to have a back-up generator just in case your renewable sources are not enough at times to keep the batteries charged.
The benefits of an off grid system is that a person can become energy selfsufficient and can power remote places away from the grid. You also have fixed energy costs and won't be getting a bill from your energy use. Another neat aspect of off grid systems is that they are modular and you can increase the capacity as your energy needs grow. You can start out with a small, budget-conscious system and add on over time.
One disadvantage is that off-grid systems may not qualify for some incentive programs. You have to also design your system to cover 100% of your energy loads, and hopefully even a little bit more. Off-grid systems have more components and are more expensive than a standard grid-tied system as well.