Oʻahu’s Real Energy System: Stripping Away Aviation, Shipping, & Military Demand

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Energy discussions about Hawaiʻi often begin with the largest numbers on the chart. Aviation fuel, maritime bunkering, and military logistics dominate many of the data tables that describe the state’s energy system. When those numbers are placed on a single chart, the scale of the challenge appears enormous and the system looks harder to change than it actually is. But much of that energy does not power homes, businesses, or vehicles that operate within the island economy. A large share fuels aircraft leaving the islands, ships crossing the Pacific, and military operations that serve national missions rather than the local population. The purpose of this analysis is to narrow the boundary. By focusing on the energy that supports daily civilian life on Oʻahu, the discussion shifts from global transportation flows to a system that local policy and infrastructure investment can influence.

Hawaiʻi is often described as a single energy system in national statistics, but it operates as a set of separate island systems connected only by shipping. Electricity does not move between islands. Each island grid must generate and balance its own power in real time. Liquid fuels move between islands by tanker, but electrical energy does not. That physical separation shapes every part of the state’s energy structure. A wind farm built on one island cannot serve another island’s load without building new transmission across open ocean. As a result, each island’s electricity supply, demand profile, and renewable resources must be analyzed independently even though the islands share a petroleum supply chain.

Oʻahu dominates Hawaiʻi’s energy demand because it dominates population and economic activity. The state has roughly 1.44 million residents and about 1.0 million of them live on Oʻahu. That is about 70% of the population. The island also hosts the state’s main commercial center, the largest airport, the primary seaport, and the only operating petroleum refinery in Hawaiʻi. When energy demand is allocated across islands using available consumption data and transportation activity, Oʻahu accounts for roughly 60% to 65% of total statewide energy demand. The difference between population share and energy share comes from the distribution of tourism, aviation traffic, and shipping activity across the islands.

The Sankey diagram provides a clear way to visualize those flows. In a Sankey diagram, each arrow represents a flow of energy measured in gigawatt hours. The width of the arrow corresponds to the amount of energy moving through that pathway. Primary energy enters the system from fuels such as crude oil and refined petroleum products and from renewable sources such as wind and solar. That energy moves through conversion processes such as refining and electricity generation before reaching end uses in buildings, transportation, and industry. At the end of the chain, the energy divides into useful energy services and rejected energy, which represents losses as heat.

The full Oʻahu energy flow diagram begins with primary energy inputs. In the baseline representation, roughly 52,885 GWh of crude oil enters the refinery and another 5,000 GWh of refined petroleum products arrive directly by ship. Renewable electricity sources add smaller contributions. Wind supplies about 290 GWh, solar contributes about 1,720 GWh, and biomass provides about 15 GWh to the electricity grid. Waste to energy contributes about 1,500 GWh of fuel input that generates both electricity and rejected heat, not to mention a significant amount of CO2, something I intend to return to in this analysis later. Environmental heat captured by heat pumps and air conditioners adds small flows of 20 GWh to residential buildings and 10 GWh to commercial buildings.

As a note on units, fundamental requirements of decarbonization are that everything that can be electrified will be electrified and all energy that can be derived from renewable sources as electricity, dominantly from wind, water and solar, will dominate energy flows. As a result, in my analyses, I choose to start at the end units of electricity, rather than current day units of fossil fuels or heat. This will make the comparison between the end state scenario I will create for Oʻahu and the current state clearer. It’s an imperfect choice as a GWh of oil cannot deliver as much work as a GWh of electricity, and so representing them as equivalent can cause confusion, but it’s the best compromise in my opinion.

Those inputs feed into the transformation stage of the energy system. The refinery converts crude oil into refined products, producing about 47,000 GWh of petroleum fuels, 800 GWh of refinery gas, and about 5,085 GWh of rejected energy from the refining process. Waste to energy plants generate roughly 340 GWh of electricity and reject about 1,160 GWh of heat. Electricity generation from fossil fuels consumes about 15,300 GWh of petroleum products and delivers about 5,340 GWh of electricity to the grid while rejecting about 9,960 GWh of heat.

Electricity then moves through the island grid to the final sectors. About 2,200 GWh goes to residential buildings, 3,400 GWh goes to commercial buildings, and 1,600 GWh goes to industrial users. Another 115 GWh supplies transportation through electric rail and electric vehicles, which seems like a lot, but only represents about 2% of transportation energy. The grid itself loses about 390 GWh in transmission and distribution. These numbers represent the portion of the energy system that is already electrified.

The petroleum system supplies the rest of the economy. The petroleum pool distributes about 34,000 GWh to transportation fuels, 600 GWh to commercial uses, and 900 GWh to industrial uses. Another 1,200 GWh leaves the system as exports or stock changes. Gas derived from refinery processes supplies 200 GWh to residential uses, 500 GWh to commercial uses, and 100 GWh to industrial uses. When all of these flows reach their final sectors, they divide between useful energy services and rejected energy. For example, the residential sector receives about 2,420 GWh of energy in total. Roughly 726 GWh becomes useful energy services such as lighting, heating, cooling, and appliance operation, while 1,694 GWh becomes rejected heat.

Transportation is the dominant energy consumer in the full system. The sector receives about 34,120 GWh of energy, including petroleum fuels, biomass fuels, and electricity. Only about 6,824 GWh becomes useful transportation services such as vehicle motion. The remaining 27,296 GWh becomes rejected energy in the form of engine heat and other inefficiencies. That 80% loss rate is typical for internal combustion engines and explains why transportation dominates the rejected energy side of the Sankey diagram.

Aviation represents the largest single component of transportation energy on Oʻahu. Jet fuel loaded onto aircraft at Honolulu International Airport supports flights to the mainland United States, to international destinations, and to neighboring islands. Passenger statistics from the Hawaiʻi Department of Business, Economic Development and Tourism show more than 7 million overseas departures from Honolulu in a typical year. Interisland departures add another 3 million passengers. When passenger counts are combined with average flight distances, it becomes clear that most jet fuel bunkered on Oʻahu supports flights that leave the local economy entirely.

Maritime shipping represents another major energy flow. Container ships, cruise ships, and bulk carriers regularly call at Honolulu Harbor. Some vessels take on fuel locally while others refuel elsewhere in the Pacific. Data from the U.S. Energy Information Administration show tens of millions of gallons of fuel sold annually for vessel bunkering in Hawaiʻi. That fuel supports both interisland cargo operations and international voyages. Cruise ships also consume substantial fuel volumes when they bunker locally before departing for other ports.

Military fuel use forms a third category that inflates the apparent scale of the island’s energy system. Joint Base Pearl Harbor Hickam supports naval operations, aviation units, and logistics infrastructure that require significant volumes of jet fuel and marine diesel. Infrastructure such as the Red Hill fuel storage facility has historically stored hundreds of millions of gallons of military fuels, although it’s decommissioned now and available for other use cases, such as a strategic biomethane reserve. Those fuels support operations across the Pacific region rather than the civilian economy of Oʻahu.

Once aviation, maritime bunkering, and military fuel use are separated from the civilian economy, the remaining energy system looks very different. Removing those flows reduces the crude oil required by the refinery and reduces the rejected energy associated with refining and combustion. The resulting Sankey diagram shows the energy required to support homes, businesses, ground transportation, and local industry. In the adjusted diagram, crude oil input falls to about 30,394 GWh from just under 53,000 GWh. Petroleum products flowing to transportation fall to about 13,800 GWh. Electricity demand remains unchanged because the local grid serves civilian and commercial loads.

When those efficiencies are applied to the island’s energy flows, the result is striking. In the civilian Oʻahu system represented in the adjusted Sankey, roughly 6,000 GWh becomes useful energy services, while more than 30,000 GWh becomes rejected energy. That means about 80% of the primary energy entering the system ultimately leaves as low value heat from engines, turbines, and industrial equipment. While the mainland is not exactly a global model of an efficient energy system, wasting two-thirds of all primary energy entering the economy, Hawaiʻi’s 80% waste of energy is the highest I’ve modeled. The dominance of petroleum fuels makes that imbalance unavoidable, and it explains why electrification has such large potential impact. Electric motors and heat pumps convert a much larger share of input energy into useful work, which reduces both fuel consumption and rejected energy even before renewable electricity is considered.

The revised diagram shows a smaller and more tractable energy system. Residential buildings consume about 2,420 GWh, commercial buildings consume about 4,510 GWh, and industry consumes about 2,600 GWh. Transportation energy falls to about 13,920 GWh once aviation and maritime shipping are excluded. The energy services portion of transportation drops to about 2,784 GWh while rejected heat falls to about 11,136 GWh. Electricity becomes a larger share of the remaining system because the largest petroleum flows have been removed.

Establishing a civilian energy baseline makes it easier to analyze electrification pathways. Once the system boundary is limited to local energy demand, it becomes possible to ask practical questions. How much electricity would be required to electrify the remaining transportation sector? How much renewable generation would be needed to replace oil fired power plants? What level of storage would stabilize the grid during periods when solar output falls? Each of these questions can be evaluated using the revised Sankey diagram as a starting point.

One implication of the Sankey diagram that often surprises readers is that an energy transition does not require replacing the full amount of primary energy entering the system. What actually matters is the useful energy services delivered at the end of the chain. The rest is rejected heat created by inefficient conversion processes. On Oʻahu the adjusted Sankey shows roughly 6,000 GWh of useful energy services and more than 30,000 GWh of rejected energy. When oil is replaced by electricity from renewable sources, most of that rejected energy disappears because electric motors, power electronics, and heat pumps convert a much larger share of energy into useful work. This is why the energy transition does not require building renewable systems large enough to replace every barrel of oil currently burned. Only the useful energy services must be replaced.

Confusing primary energy with useful energy demand is known as the primary energy fallacy. The error appears often in public discussions of the energy transition, including in the work of influential analysts such as Vaclav Smil, whose analyses frequently compare renewable supply requirements against current primary energy consumption without accounting for the much higher efficiency of electrified systems. Smil only acknowledged this in the early 2020s in a brief paper, and never adjusted his oft cited publications or admitted that his analysis was based on false assumptions. When the comparison is made correctly, the scale of the transition is still large but substantially smaller than primary energy accounting suggests. As I noted in my analysis in 2022, US energy requirements would plummet by 50% with electrification of the economy and renewables. The same analysis is going to be applied to Oʻahu.

The purpose of separating these flows is not to ignore aviation or shipping. Those sectors remain major contributors to global emissions and will require their own transition strategies. Sustainable aviation fuels, new propulsion systems, and operational efficiency improvements will play roles in those sectors and I’ll explore them for Oʻahu. Military operations are also examining alternative fuels and efficiency measures, but I’ll leave that out of the assessment.

Focusing first on the civilian energy system on Oʻahu clarifies what local decision makers can influence directly. The energy required to run homes, offices, shops, and vehicles on the island is large but manageable. It represents a fraction of the total energy flowing through the refinery and fuel distribution network. By isolating those flows, the analysis reveals a realistic pathway for electrification and renewable energy expansion that addresses the part of the system that local policy can change.