By the PPA Funding team Last updated
No. A standard grid-tied solar system shuts down automatically during a power cut. This is a safety feature that stops it feeding electricity into cables that engineers may be repairing. To keep power on, you need a battery with backup or islanding capability that can safely disconnect from the grid.
Why does grid-tied solar switch off in a power cut?
Grid-connected inverters are required to stop generating the moment they detect the grid has gone down. The function is called anti-islanding protection, set out in engineering standard G99 (and G98 for smaller systems). Without it, a solar system could keep energising the local network and put line workers repairing a fault at risk of electric shock.
Because this shutdown is automatic for a standard export system, having solar panels alone does not give you resilience against blackouts. On a sunny day with the grid down, an ordinary system simply sits idle.
What lets a system keep running during an outage?
Keeping the lights on needs battery storage paired with an inverter that supports backup, sometimes described as islanding or an uninterruptible supply. When the grid fails, the system safely disconnects the building from the network, then runs selected circuits from the battery and recharges it from the panels during daylight.
Not every battery offers this. Some are designed only to store cheap or self-generated energy and will also shut down in an outage. If continuity matters, specify backup capability up front, and decide which circuits or loads you need to protect.
Is backup power worth it for a business?
Backup makes most sense where an outage is costly or disruptive, such as cold storage, servers, care settings or production lines. The battery is sized around the loads you must keep running and how long you expect to bridge, so the design starts from your critical circuits rather than the whole building.
Under a funded arrangement the resilience benefit is separate from the running-cost saving, so it helps to be clear about which you are buying. A feasibility study can weigh the added cost of backup against the value of avoided downtime for your site.
This guide is general information, not financial or tax advice. Your circumstances determine what applies — please confirm with your accountant or advisor. Get a tailored proposal →
Frequently asked questions
If I have solar panels, will they power my building in a blackout?
Not on their own. A standard grid-tied system shuts down for safety when the grid fails. You need battery storage with backup or islanding capability, plus an inverter that supports it, to keep chosen circuits running during an outage.
Does adding battery backup mean my whole site stays on?
Usually not the entire site. Backup is normally designed around critical circuits, such as lighting, refrigeration or IT, so the battery lasts long enough to matter. Sizing depends on those loads and how long you need to cover, which a feasibility study can work out.
Related guides
- Solar for multi-let commercial buildings: sharing generation between several tenanted units
- How to choose a commercial solar provider: accreditations, questions and red flags
- Building-Integrated Solar (BIPV) for Business: Solar Built Into the Building Fabric
See our funding options, commercial solar and solar by industry pages.