Each solar setup has its own benefits and limitations, and it is important to gain a real understanding of these before you invest in a potentially expensive solar PV system, to help avoid disappointment further down the line.
Grid tied solar PV Systems
99% of solar systems installed on peoples homes are whats known as grid tied systems. These grid tied systems allow you to take advantage of the free electricity you create from the solar PV system as well as the the electric grid. This gives you much more flexibility, since you are not reliant on the sun shining to allow you to use electricity – you can use as much electricity as you want at any time.
Any shortfall in supply from the solar PV array can be met by additional electricity supplied via the grid, but there is also the added benefit of being able to sell any surplus back to the grid. In essence, a grid tied system will go someway to reducing your dependence on the utility companies, and also give you some money savings (obviously any electricity supplied from the grid needs to be paid for), but will give you the comfort of 100% supply from the grid if something were to go wrong. These systems are also simple to install and are less problematic than other types of solar PV installation due to their lack of batteries.
Grid tied solar PV installations have become incredibly popular in the UK recently due to generous government subsidies (guaranteed for 25 years from the date of installation). They do help reduce your reliance on the grid, and also reduce your electricity bills. However you still need to be connected to the grid for this system to work effectively.
Off grid/standalone solar PV systems
Producing 100% of your own electricity in a clean and sustainable manner is the dream scenario for many people; the thought of never paying another electricity bill, and never suffering from grid blackouts is obviously a very attractive proposition.
However an off-grid system does not need to be this sophisticated and grand in scale, it can simply power a light in your garden shed, or a water fountain in your garden. For this reason, the off-grid installations are in fact the most common type of solar installation across the globe, providing electricity to any isolated location, normally where no other electricity source is readily available.
The disadvantage is that you essentially become the utility company, so any costly repairs fall under your remit. If there is a problem with your supply for any reason, you will not have electricity. Solar power is also an intermittent source (not producing power 100% of the time), so if you need electricity during the night (for lights in your house etc.) you will need to install batteries within your system, that enable you to store energy during the day and use this when you are not producing.
The rewards for installing an off-grid system are clear, however the increased responsibility of owning your homes electricity supply could make this a potentially daunting task for solar PV beginners.
Grid tied with battery backup systems
The issue with this system is its added complexity compared to the grid tied solar PV system described above. The batteries will require additional maintenance and add significantly to the final cost of the system, and they will also introduce additional inefficiencies within your system – potentially a 15% loss in overall performance.
Grid fallback systems
Electricity is taken from the batteries and run through an inverter to provide the electricity required in the home. Once the batteries begin to go flat, the system automatically switches over to grid power, allowing the solar panels to once again charge the bank of batteries, and the process starts again.