Optimise your solar system and save big this South African summer

Most home solar systems in South Africa were originally configured for load-shedding – and if you haven’t made changes since load-shedding stopped, you are leaving money on the table.

This is according to Marc du Plessis, executive head of the LookSee home efficiency platform, who explained that just because your solar system is still running smoothly, doesn’t mean you are getting its full value.

• Click here for more home efficiency tips from LookSee.

“With electricity tariffs rising, families need their solar systems to deliver maximum savings on their electricity bills,” said du Plessis.

“However, many simply just don’t know what to do to make this happen. That’s why we’re sharing the top tips we give our own solar customers.”

Battery usage

Most South African solar systems are configured to keep the battery charged to between 80% and 100% of its capacity whenever load-shedding is not happening.

This was appropriate in the context of load-shedding, when it was critical to have enough backup power stored to get you through even the longest outages.

However, with load-shedding having been gone for over seven months, there is no need to keep such a large amount of backup energy stored.

“If you don’t have to worry about load-shedding, then you can start using this battery storage for your family’s nighttime needs. This will mean you have less reliance on the grid and far more savings on your electricity bill,” said du Plessis.

See this example:

• Your battery is set to always have at least 80% of its capacity stored.
• You run intensive appliances – like washing machines or dishwashers – that push your battery down to this limit.
• To keep your appliances powered without depleting your battery lower, your inverter draws electricity from the grid – costing you money.
• To get your storage back to 100%, your battery is charged using grid power – costing you money.

In an alternative scenario where you let your battery deplete to 40%:

• Your battery is set to always store at least 40% of its capacity.
• You run intensive appliances – like washing machines or dishwashers – that push your battery down to 60% capacity.
• Because you have not reached your minimum battery threshold, you do not draw electricity from the grid.
• Your battery is set to only charge with solar power ensuring extra grid power is not consumed.

Using the above example, it is clear that adjusting your battery’s minimum threshold can be a big money saver.

To determine how low you should set your minimum threshold, check your battery manufacturer’s recommended depth of discharge (DoD) setting.

If your battery has a recommended DoD of 80%, this means you can use up to 80% of its capacity before inefficiencies arise.

Then add a safety factor for unexpected power outages of 10-20% to determine how much of your battery’s capacity you can use.

For example: If a battery has a recommended DoD of 80%, and you wan to include a 20% safety factor, you can deplete up to 60% (80% DoD – 20% safety factor) of your battery.

In other words, 40% of your battery’s capacity must be charged up at all times.

“You should also ensure your batteries only recharge with solar power,” said du Plessis.

“This prevents drawing additional electricity from the grid, and ensures you don’t waste the free electricity generated by your solar panels.”

Load scheduling

Another important way to optimise the extra sunshine of summer is through effective load-scheduling.

“While your solar panels will start generating power earlier in the day, it still takes time for the sun to get to a position where they can produce at their best,” explained du Plessis.

“This is called a peak operating period and typically happens between 9:30 and 15:30.”

It is highly advisable to schedule your most electricity-intensive tasks during this peak operating period.

Additionally, you should spread these tasks out throughout the peak operating period as much as possible.

This is because running several of these loads simultaneously could result in your electricity draw being more than your solar panels can produce – leading to additional power draw from the grid to compensate.

For example: If you have installed 2.5kW of solar panels, and simultaneously run a dishwasher that draws 1.8kW and a washing machine that draws 1kW, you will be drawing more electricity than your solar panels generate – and this is before accounting for any other energy draws like fridges and freezers.

“Pay particular attention to loads that can be moved to the afternoon – like your geyser, pool pump and vacuum cleaning – as this is the time when your household electricity demands tends to drop off,” said du Plessis.

Thanks to the increased sunny periods of summer, your solar panels will fill your battery up quickly in between these loads, as well as once they are done.

This will ensure you still have more than enough battery power for the night ahead.

Panel maintenance

It is also important to keep your solar panels operating at full capacity – as failure to do this is leaving money on the table.

Solar panels are installed in strings – so if even one of your panels is not operating efficiently, it will impact the generation of all of your panels.

There are two common scenarios where solar panels don’t operate at maximum capacity:

• Dirty panels – Built-up dirt and bird droppings can lower the efficiency of your panels.
• Shade – Overgrown branches and leaves can block sunlight from reaching your panels during certain periods of the day.

In both cases, the solution is easy – cleaning your panels or trimming the branches and leaves, respectively.

Click here for more home efficiency tips from LookSee.