Electricity on a small island: generation, cost and reliability

Electricity in a small island state is expensive, and the reasons are structural rather than administrative. An isolated grid serving a small population cannot access the economics that make power cheap elsewhere.

Why an isolated grid is different

A grid with no interconnection to neighbours must meet every megawatt of its own demand at every moment, with its own reserve margin.

Consequences:

• Reserve capacity must be held locally, and it is idle most of the time
• No import during a shortfall or a plant outage
• Small generating units, which are less efficient per unit than large ones
• Full system costs spread across a small customer base

The last point is the core of the tariff question. The fixed costs of generation, transmission and distribution are divided among relatively few customers, so the per-unit share is high before any fuel is burned.

Fuel dependence

• Generation depends substantially on imported petroleum products
• Fuel cost passes through to tariffs, often via an explicit surcharge
• World price movements therefore reach household bills quickly
• Freight to a small market adds cost per unit
• Storage capacity limits the ability to buy ahead

This is the transmission channel described in the material on prices. An oil price movement reaches electricity bills, then transport costs, then the price of everything else, with very little delay and no domestic buffer.

Renewables: the real constraint

The resource is not the problem. Solar irradiance is good, there is geothermal potential in the volcanic geology of the region, and wind resources exist.

The constraint is grid stability:

• Small grids have low inertia, so frequency is more sensitive to fluctuation
• Intermittent generation destabilises a small system faster than a large one
• Storage is therefore a prerequisite rather than an enhancement
• Existing thermal plant must still be maintained for backup
• Capital cost is high relative to a small customer base

The key point that outside commentary often misses: on a small isolated grid, adding solar without storage does not simply displace fuel — beyond a modest share it threatens stability, and the storage requirement dominates the economics.

The fourth point is also frequently overlooked. Renewable capacity does not remove the need to maintain thermal plant for periods without sun or wind, so the system carries both sets of fixed costs during transition.

Reliability

• Outages occur, and are usually short
• Storms cause the significant disruptions, with overhead lines vulnerable
• Terrain makes restoration slow in remote areas
• Undergrounding improves resilience at high capital cost
• Backup generation is common in businesses and some households

The second connects to the disaster discussion elsewhere in this reference. Restoring an electricity network after a major hurricane is a months-long undertaking, and during it every system depending on power — water treatment, cold chain, health facilities, communications — operates degraded.

Reading energy data

1. Distinguish installed capacity from generation
2. Note whether self-generation is included
3. Check whether tariffs are inclusive of the fuel surcharge
4. Read renewable share as generation, not as capacity
5. Note losses, technical and commercial
6. Compare with other small island systems

Point four is the most misleading distinction in energy statistics generally. A high renewable share of installed capacity can coexist with a low share of actual generation, because intermittent capacity produces only when conditions allow.

Frequently asked questions