Canada's solar and clean energy sector is growing faster than most manufacturers' export paperwork can keep up with. Battery Energy Storage Systems (BESS), transformers, and solar inverters are all shipping by air in higher volumes, and nearly all of them qualify as Dangerous Goods (DG) under IATA regulations.

Most equipment manufacturers plan around production schedules and freight bookings, not hazard classification. That's the bottleneck: a fully built BESS unit or inverter can sit at the cargo warehouse for days, or get turned away outright, because the State of Charge wasn't verified, the packaging wasn't UN-specification, or the Shipper's Declaration wasn't prepared correctly.

Here's what actually applies when you're moving power and solar equipment through Toronto Pearson (YYZ).

1. Battery Energy Storage Systems (BESS): UN 3480 and Class 9

High-capacity LiFePO4 and lithium-ion Battery Energy Storage Systems ship under UN 3480 as Class 9 dangerous goods. That classification triggers three requirements before the cargo can be accepted:

  • UN-specification packaging matched to the hazard class.
  • An IATA Shipper's Declaration prepared to Class 9 requirements.
  • Verified State of Charge compliance before the unit is packed.

BESS units don't move on standard commercial paperwork. If any one of these pieces is missing or incorrect, the airline will refuse the shipment at the counter. This is the most common failure point we see from first-time exporters in this sector: the battery chemistry and capacity are correct, the unit itself is built to spec, but the packaging and documentation were prepared as if it were general freight instead of Class 9 dangerous goods.

Whether you're shipping a single BESS unit for a pilot project or a recurring run of units for a larger installation, the classification requirements are the same. Confirming the equipment type, battery chemistry, and destination up front is what lets the correct UN classification get locked in before packaging even starts.

2. Transformers and Insulating Liquids: Class 3 and Class 8

Transformers and other power equipment containing dielectric or insulating liquids fall under Class 3 (flammable liquid) or Class 8 (corrosive) hazard rules, depending on the specific fluid involved. This applies regardless of how the transformer itself is classified, because the liquid inside it carries its own hazard profile.

That means transformer shipments need:

  • Hazard-compliant packaging matched to the fluid's classification.
  • Documentation prepared before the unit can be tendered for air cargo.

Skipping this step is one of the more common reasons transformer shipments get delayed. The equipment itself may look routine, but the insulating liquid inside it is what determines the paperwork. Two transformers that look identical from the outside can carry different dielectric fluids and end up under different hazard classes, so the fluid itself always needs to be identified before the packaging and documentation can be finalized.

3. Solar Inverters with Built-In Lithium Batteries: UN 3481

Solar inverters and controls with a lithium battery contained in the equipment ship under UN 3481. These can move as Cargo Aircraft Only (CAO) freight, but only once:

  • Overpack labelling is applied correctly.
  • A red-hatched Shipper's Declaration is prepared and tendered through YYZ.

The lithium battery inside the inverter is what drives the classification, not the inverter housing or the rest of the equipment. Treating an inverter shipment like a standard electronics export is how these get rejected at the warehouse. Because UN 3481 covers a battery contained in equipment, the classification travels with the finished, assembled unit rather than the battery on its own, which is easy to overlook if your export process was built around shipping electronics that don't carry a power source at all.

4. The 30% State of Charge (SoC) Rule

Lithium batteries shipped by air, including the cells inside BESS units, generally need to be at 30% State of Charge (SoC) or below to meet air transport requirements. This applies across the battery-powered equipment covered here, not just standalone battery shipments.

SoC verification has to happen before packaging, not after. A battery charged above the threshold at tender time is a guaranteed rejection, regardless of how correct the rest of the documentation is. Verifying SoC compliance is part of preparing the packaging and Shipper's Declaration for any battery shipment.

For manufacturers, this usually means building an SoC check into the production or pre-shipment process itself, rather than treating it as something to confirm the day the shipment goes to the airport. Discharging a fully charged BESS unit or inverter down to the required threshold takes time, and that time needs to be planned into the shipping schedule rather than discovered at the cargo counter.

5. Cargo Aircraft Only (CAO) and What It Means for Timing

Several categories in this sector, including solar inverters under UN 3481, are restricted to Cargo Aircraft Only freight. That has direct implications for how you schedule a shipment:

  • CAO cargo requires overpack labelling specific to the restriction.
  • It needs a red-hatched Shipper's Declaration prepared correctly the first time, since color prints with the proper hatched border are non-negotiable at tender.
  • It has to be coordinated through the YYZ freight tender process for the specific flight it's booked on, since not every routing carries CAO capacity.

Build CAO restrictions into your shipping timeline early. A shipment that's ready in every other respect can still miss its flight if the CAO booking wasn't confirmed in advance.

6. How AÉRO-DG Keeps Power and Solar Equipment Moving Through YYZ

At AÉRO-DG Solutions, we work with BESS manufacturers, transformer and power equipment suppliers, solar inverter exporters, and clean tech logistics teams shipping out of the Greater Toronto Area. Through our power & solar energy DG services, we handle:

  • UN 3480 and UN 3481 classification and UN-specification packaging.
  • Class 3 and Class 8 compliance for transformer insulating liquids.
  • 30% SoC verification for lithium battery shipments.
  • Overpack labelling and red-hatched Shipper's Declarations for CAO tender.

If you're exporting solar energy storage, transformers, or power equipment out of Toronto and need certified dangerous goods documentation before your next YYZ cargo booking, get in touch with AÉRO-DG and we'll walk through the classification and packaging requirements for your shipment.