Can solar panels power your home during a blackout?

By Martin Desmond, Wizer Energy CEO

Solar Panels are now relatively common throughout Ireland. Figures obtained by Wizer Energy show that 4,078 applications were made to the SEAI's Domestic Solar PV Scheme in 2021, with a further 2,694 applying in 2022 so far.

But are users getting the most out of their systems?

Solar panels can generate electricity and when combined with a storage battery, excess energy that is generated can be stored for later use, effectively powering your home.

In the event of a blackout you would think you’d be safe if you had such a rig installed on your property, however this may not be the case.

We’ve got more and more people asking us at the moment if they can use their solar panels to power their home when the grid goes down, unfortunately for most people here, the answer is actually no.

Regulations require that something called a shunt or fireman switch to be fitted to the power cabling running to your solar panels. It is effectively an on/off switch.

So, when the battery voltage in your home is low and needs a charge, the switch turns on and energy flows from the panels to the battery. Inversely, when the battery voltage is high (e.g. full) the switch turns off and the charging process stops.

In the case of a blackout, the shunt will disconnect the DC feed as no energy from the grid is getting to your inverter, which in turn stops any generation from taking place.

The good news for panel owners is that this issue can be resolved. The shunt can actually be safely bypassed in order to enable off grid living. This is only possible when using a hybrid solar inverter (solar & battery) and not a solar only inverter.

However, there are different modes or levels of being able to operate off grid, depending on the inverter make and model as they do offer differing solutions.

Firstly, for all off grid operations, there is a legal obligation to install a changeover switch on the premises to ensure that everything complies with electrical contracting and wiring regulations.

This simply detaches the home from its grid connection, thereby islanding or isolating the house so it now becomes its own microgrid. Even though you’re not successfully generating, storing and using your own power during a blackout, it’s vital that you adapt your daily routine and usually energy usage habits so as to not completely drain your batteries. It is important to point out that operating off-grid is a far different situation to the normal on-grid situation.

Running off grid requires an approach where essential services only are left in use, like your fridge and water pump. Other, more non-essential/ high power appliances such as water heaters/hairdryers are to be avoided as they significantly increase the risk of draining your available battery storage, in the case of a blackout you’d ideally want to forgo the use of these items.