Can a solar system reduce my electricity bill to zero?
Off grid solar systems with battery back up can produce zero electricity bills (as shown in image)
A solar system can help you reduce your electricity bill and in many instances by a significant amount, if you use the electricity at the time it is created. Nevertheless zero dollar future bills are next to impossible to achieve nowadays other than with off grid systems.
In Australia with Net Metering (explained in other parts of the FAQ's), the electricity produced though your solar system is fed directly during the daytime into your home, office or commercial enterprise. This helps you to offset your consumption which you would have otherwise paid for. The bigger the system the more likely it will be that more solar power is generated than is used and the excess will be fed back into the grid.
The feed-in-tariff payment for the electricity you generate and feed back into the power grid can offset some of the cost for the electricity you use from the grid during overcast or rainy days or at night. Nevertheless because the feed in tariff nowadays is relatively low, 5c or so per kWh, you need to feed a lot of solar electricity back to the grid in order to offset the electricity you use at night or during cloudy and rainy days when you are likely to import electricity. Then to get a zero dollar bill you will also need to export enough solar electricity to pay the $70 of service/supply charge the electricity companies charge every three month.
This scenario and basic principle does not change if your solar system uses a string inverter or a micro inverter set up. In short, a well designed solar system will reduce your electricity bills, but a zero bill now that there is no more generous "premium" feed in tariff for new systems - is very rare. Zero dollar bills require an off grid system with batteries or a very very large solar system on your home, preferably with storage batteries.
The installation of batteries to a Solar System will enable power from the system to be stored and used at night or during high demand periods, This increases the ability to reduce electricity bills to zero. However, the cost of batteries, although it has reduced, is still relatively expensive. So for most situations these are not yet financially beneficial. With advances in technology and increases in economies of scale as more batteries are purchased, pricing of batteries will reduce over the next couple of years and will become a more viable alternative to add to Solar Systems.