What does a transformer look like and why does it matter for solar?
Knowing your transformer type and kVA rating helps solar providers determine your maximum system size and whether an upgrade will be needed.
Transformers are devices that increase or decrease voltage to distribute power efficiently. If you're evaluating solar for your building, identifying your transformer and its capacity is one of the first steps in understanding what size system your site can support.
Pad-mounted transformers are the most common type at commercial buildings with larger energy consumption. They're usually big green or grey boxes located outside, sometimes with heat sinks (accordion-like fins) on the side or back. These typically have a nameplate or sticker showing the kVA (kilovolt-ampere) rating — that's the number your solar provider needs.
Pole-mounted transformers serve buildings with lower consumption. These are attached to distribution line poles near the property. If you have a pole-mounted transformer, it has a standard kVA rating and is generally less likely to be a constraint on system size.
Station and sub-station transformers are used in larger commercial and industrial settings with higher voltage and power requirements.
Why does this matter? Your transformer's kVA rating sets an upper limit on your solar system's size. If the proposed system exceeds that capacity, you'll need a transformer upgrade — and that cost falls on the building owner, not the utility. Knowing this upfront helps you get more realistic proposals and avoid budget surprises during project development.