Understanding the different system setups available.

These systems use an off-grid inverter, also known as a Stand-alone Inverter, they convert direct current (DC) from the Solar panels into alternating current (AC), which is then used to charge batteries or power appliances.
These inverters normally do not interface with the municipality grid and therefor, do not have to match phase with the utility sine wave.

Any excess Photovoltaic (PV) supply not used by appliances will be stored into batteries, if batteries are full, the excess supply is wasted.

These systems use a grid-tied inverter. They match phase with your utility sine wave and are designed to turn off upon loss of utility supply.
They do not support backup storage (no battery backups) and will therefor leave you with no electricity during load shedding.
The advantage to using this system is that any excess PV supply that is not used by your appliances will be sold to the municipality at the municipalities export tariff, each of these credits can then be repurchased at a fraction of the normal electricity cost. Municipalities provide an import tariff per kWh for this transaction.

In South Africa, there is a rental rate that must be paid to your municipality in order to utilize these tariffs with your excess PV supply.
The inverters we use in our calculations are likely to support either a Zero-Export or an Export limiting feature, which allows you to opt out of feeding excess energy to the grid and paying the municipality's Feed-in tariffs, should the selected kit not overcome the rental cost.

The best of both worlds. These inverters not only allow you to utilize both battery storage and the utility grid, but can run independantly from each other. This means that if the utility supply is cutoff, it will switch to batteries. In the event of no storage or PV supply, these will use energy from the grid.
These inverters can also export energy back into the grid, and import those credits should you pay your municipality's rental cost.
Another advantage is that the size is independant of load in normal use i.e. If you have a 3kW Inverter and a 5kW load, the missing 2kW will be seamlessly drawn from the grid. So the size of this inverter should only need to consider the output peak of your Solar PV system or your essential appliance load.

These work very similar to Hybrid systems, on a basic level, except for a few key differences.

• The system cannot run without batteries.
• The system cannot export excess energy back into the grid.
• The inverter has to be sized for maximum load. If you want to draw 5kW you need a 5kW inverter.