After every major storm, the same question echoes across Bermuda: why doesn’t Belco put all its electricity lines underground? It’s a fair question, but the reality is far more complex, and the associated costs are far greater than it might appear.

As an electric utility, Belco’s responsibility is straightforward: to deliver safe, cost-effective, reliable power supply to homes and businesses across the island. Achieving the high levels of reliability that Bermuda has become accustomed to requires balancing engineering practicality, cost-effectiveness, speed of repair and the physical realities of Bermuda’s densely populated residential neighbourhoods.

More is underground than most people think

A common misconception is that Bermuda’s electricity system is mostly overhead. In fact, 100 per cent of Belco’s high-voltage transmission network has been underground for decades. The continuing transmission upgrade project involves the replacement of ageing cables, many of which are more than 50 years old. The transmission network takes the power generated from the central power generation station and transmits it at 33 kilovolts (kV) or 22kV to 34 substations across the island.

The transmission network runs under main roads with pairs of cables to build redundancy into the system. This means that if there is a single transmission cable fault, the power can be routed on the alternate cable and under normal operating conditions, customers will not be affected.

At the substations, the transmission network voltage is then stepped down to the 4kV distribution network, 40 per cent of which is already underground. For example, large portions of the City of Hamilton operate fully on underground feeders, and Belco continues to bury cables where it is the most practical and beneficial solution.

Along the 4kV distribution feeders, there are transformers that step the voltage down to the required service voltage for your home or business. New construction projects and customer-driven upgrades are also steadily increasing the number of underground low-voltage services across the island.

Why overhead lines still make sense in many areas

The question, then, isn’t: “Why hasn’t Belco undergrounded everything?” It is: “Why isn’t everything underground yet — and should it be?”

The answer lies in reliability and redundancy. In the City of Hamilton, where there are multiple streets running in block-like structures that allow for well-defined cable routes, underground systems work well because there are alternate pathways for electricity to reach customers if one cable fails.

In densely populated residential areas, however, installing multiple underground cables to give greater flexibility and redundancy is often impossible. If an area relies on a single underground cable and that cable faults, the power cannot be rerouted, meaning customers can be without power until crews locate the fault, excavate the section of faulted cable, repair the damage, and reinstate the trench. This process involves mobilising multiple teams, including contractors, to perform the excavation work, and takes significantly longer than repairing overhead lines.

In other words, undergrounding without built-in redundancy can actually decrease reliability for many neighbourhoods.

The cost reality: why full undergrounding isn’t practical

Cost is often the most underestimated factor with undergrounding an electric power grid. In 1998, engineers estimated that undergrounding Bermuda’s entire distribution system would cost about $220 million. Adjusted for today, that figure is closer to $440 million.

Those are just the installation costs. Underground systems have:

• more expensive repairs

• higher long-term replacement expenses

Typically, undergrounding costs five times more than overhead options. Undertaking full island-wide undergrounding would also require approval to trench through both public and private land, along with careful co-ordination among multiple utilities to avoid repeated disruption.

The result would be years of construction, island-wide inconvenience and a significant increase in electricity costs for all customers.

What homeowners and businesses can do

For those who prefer underground service to their property, Belco can evaluate individual requests on a case-by-case basis, provided the customer covers the cost and arranges the trenching and laying of cable duct. This allows undergrounding to expand organically, in ways that are both cost-efficient and technically feasible.

The real driver of storm outages

During storms, the majority of outages are not caused by overhead distribution lines failing; they’re caused by vegetation coming into contact with them, which can cause protection systems to operate and circuits to trip. Heavy, wet palm fronds, branches and trees can also pull lines and poles down.

Tree trimming is one of the most effective ways to reduce storm-related outages. Customers can arrange for Belco to safely shut off power so that homeowners can facilitate trimming, with at least three weeks’ notice.

Working together to maintain safe clearances helps to significantly reduce outages throughout the year.

Securing loose objects such as lawn furniture, toys, kites, balloons and even trampolines that can become airborne and entangled in overhead power lines is another effective way to ensure that the power supplies are not interrupted.

A balanced, responsible path forward

Bermuda already benefits from a fully undergrounded transmission system and a distribution network that continues to be buried where it makes sense technically, financially and geographically. Belco will continue to underground lines where the benefits outweigh the costs and where reliability can be maintained or improved.

To transform the entire island’s electricity network into a fully underground system would require billions of dollars over time, extensive public disruption, and in many cases would not improve reliability.

The smarter approach for customer rates and for Bermuda’s energy future is to continue evaluating each area thoughtfully, investing where undergrounding provides the greatest value and makes sense to all stakeholders, and maintaining a reliable grid designed for both everyday operations and severe weather.

• Jeffrey Steynor is director of energy transition and business development at the Bermuda Electric Light Company