While many solar users assume that their system will continue to power lights and electricity in the event of a hurricane, storm or blackout – or in any situation when the main grid is down – the reality is that it depends on the specific type of system owned.
In a recent blog post, Southern Current – one of the top solar installers in South Carolina – said the only way to be completely sure your solar installation will hold up in a blackout, hurricane or storm, is to be 100% off the grid – but due to the expense, this isn’t the most common option for Americans.
According to Southern Current, the most likely result, if and when the grid goes down, is that the solar array shuts down as well. This is due to the National Electric Code (NEC) that stipulates the system must shut down for safety reasons – specifically, to prevent workers from getting electrocuted.
“If the power source – your photovoltaic solar panels – continued to be energized when the sun was shining, it could generate and send solar electricity into the power grid and potentially electrocute persons working to restore power after a blackout,” Southern Current wrote. “So, per the NEC code, the inverter is designed to shut down during a blackout or loss of grid power. Without a functioning inverter, not a single electron will flow in to or out of the house.”
Southern Current estimates this is what happens with about 99% of the systems installed in America, which are grid-tied solar power installations. However, there are a few exceptions – systems that are designed for semi-off-grid and off-grid living.
New storage technologies
The first exception is a system that incorporates backup batteries with AC coupling systems. AC coupling allows the energy generated from solar to be stored in a battery and used independently of the grid. Enphase Energy – a well-known microinverter installation company – has developed an AC energy storage unit that can be retrofitted into existing solar installs.
AC coupling is a relatively new technology, but Southern Current predicts it will become more and more popular in the future as utilities change the way they charge their users for power, like with time of use (TOU) billing tiers being implemented in California and Hawaii. In this scenario, an AC coupled solar power system could be programmed to store solar energy when rates are low, using it to power the home when utility rates are at their highest later in the day (a term referred to as ‘peak shaving’ or ‘rate arbitration’).
The second and least common scenario is using off-grid solar power system. This setup would involve being 100% independent from the local power grid – generating 100% of electricity requirements from the solar system, and storing all of this electricity in a bank of batteries connected to the home’s electrical system. The benefit of being 100% off grid is that there is no need to adhere to NEC codes; as such, the system would not have to shut down during a disaster or blackout because it would never be sent back into the grid. However, this is the most expensive option.
“The bottom line is that a solar power system can be designed to provide you with electricity during a blackout, but it will cost extra, and at this time it’s not too popular,” Southern Current wrote. “Adding batteries to a standard solar installation can cost thousands of extra dollars. Although blackouts are a pain, they don’t happen too often and generally get resolved in under 24 hours.”
That being said, Southern Carolina runs a number of solar rebates and incentives to reduce the costs of installing and running solar systems, and the popularity of solar installation for home or business in the state is rising each year.