A well designed and installed solar system can be a valuable asset to your home or business. But with the high cost of installation, it can also be a large waste of money…. here are some issues to think about to maximise the potential of a solar system.
Batteries vs Grid-Tied
An important decision to make is whether to use a battery or not. A grid-tied system (see below) is the least costly system to install and results in the greatest return on investment. However, it does not operate during load-shedding or at night. A battery system will provide power when the grid is not available or at night, but adds significantly to the cost of the system.
The Grid-tied Solar System
A grid-tied solar system feeds solar electricity onto your existing electrical board. This electricity will flow to the loads on that board (e.g. geysers, computers etc), and, if there is extra power, it will flow back to the grid (Eskom or the municipality). If there is not enough solar electricity, grid electricity will be used.
The advantage of this system is that it is the least expensive. The disadvantage is that it cannot operate without the grid, and the power is not stored in a battery for night-time consumption.
the Battery System
Battery systems cost more, and are more costly to install. However, modern lithium batteries, properly designed and installed, can provide you with electricity that is cheaper than grid-power.
The important points in selecting a battery for your system:
- Size: What size battery do you need?
- Cycle life: How many cycles (charge and discharge) will the battery last?
- Power: Can the battery deliver the power that you need?
- Safety: How safe is the battery (risk of explosion)
An important issue in solar design is self-consumption or the percent of the electricity generated by your solar system that will be consumed by your property or business. For example, if your solar system is producing 1000W and your home is only using 300W, the remaining 700W must either go into a battery or go to the grid (Eskom). If it cannot, it will not be produced.
In municipalities where you can “sell” your excess solar power to the grid, you earn significantly less than it costs you. For example, the City of Cape Town pays 98c per kWh sold to them, but can charge R2.98 on the top tier of the Home User Tariff.