How the Hawaiian Power Grid Works

In January of 2024, right on the heels  of a serious drought across the state,  

a major storm slammed into the Hawaiian islands  of Oahu and Kauai. Severe winds caused damage to  

buildings, and heavy rain flooded roadways.  At the Waiau Steam Turbine plant,  

the rain reached some of the generator unit  controls, tripping two units and knocking 100  

megawatts of power off the tiny grid (roughly 10%  of demand). The overcast weather also meant solar  

panels weren’t producing much electricity, and the  colossal battery systems at Kapolei

and Waiawa were running out of juice.  Other generating units were out of service due to  

maintenance scheduled during the cool winter  months when power demands were lowest. Then,  

the H-POWER trash-to-energy plant tripped  offline as well. By the evening of January 8th,  

all of Hawaiian Electric’s power  reserves on Oahu were depleted,  

and it was clear that they weren’t going to have  enough generation to meet all the needs. And if  

you can’t increase supply, the only other  option is to force a reduction in demand.

At around 8:30 PM, the utility implemented rolling  outages across the island of Oahu to bring power  

demands down to a manageable level. For about 2  hours, the utility blacked out different sections  

of the island for 30 minutes each to minimize  the inconvenience. Twice since then, as of  

this writing, rolling outages have been forced on  Hawaii Island from unexpected trips at generators  

and scheduled maintenance at backup facilities,  making them unavailable to pick up the slack.

When we say “power grid” we’re used to imagining  interconnections that cover huge areas and serve  

tens to hundreds of millions of people. But  populated islands need a stable supply of  

electricity too. Those recent power disturbances  highlight some really interesting challenges that  

come from building and operating a small  power grid, so I thought it would be fun  

to use the 50th state as a case study to  dive into those difficulties. I’m Grady,  

and this is Practical Engineering. Today  we’re talking about the Hawaiian power grid.

Really, I should say Hawaiian power grids,  because each populated island in the state  

has its own separate electrical system. Around  95% of customers are served by a single utility,  

Hawaiian Electric, which maintains grids  on Oahu, Maui, Hawaii Island, Lanai,  

and Molokai. Kauai is the only island with its  own electric cooperative. There have been a few  

proposals and false starts to connect the islands  through undersea transmission cables and form a  

single grid. It is an enormous challenge to  install and maintain cables of that depth  

and distance. When you add in the volcanic and  seismic hazards of the area and the sensitive  

ecology of the surrounding ocean, so far, no  one has figured out how to make it feasible. So,  

each island has its own power plants, high-voltage  transmission lines, substations, and distribution  

system entirely disconnected from the others.  And that makes for some interesting challenges.

“Reliability” is the name of the game  when it comes to running an electrical  

grid. It’s not that complicated to build  generators, transmission lines, transformers,  

et cetera. What’s hard is to keep them all  running 99.9% of the time, day and night,  

rain or snow. Yeah, some parts of Hawaii  occasionally get snow.

This is a graph of a typical reliability curve that helps explain why  it’s a challenge. At the left end of the curve,  

you can get big increases with a small investment.  But the closer you get to 100 percent uptime,  

each increment gets a lot more expensive.  It really boils down to the fact that,  

in many ways, reliability comes from  redundancy. When something goes wrong,  

you need flexibility to keep the grid up. But,  in practice, that means you have to pay for and  

maintain equipment and infrastructure that rarely  gets used, or at least not to its full capacity.

Hopefully, it’s clear that the graph I  showed is idealized. It’s much harder  

to put concrete numbers to the question.  The random nature of problems that arise,  

our inability to predict the future, and the  fact that everything in a bulk power system is  

interconnected all make it practically impossible  to know how much investment is required to achieve  

any incremental improvement in reliability.  But it’s useful anyway because the graph helps  

clarify the benefits of a large power grid,  also known as a “wide area interconnection.”

For one, it smooths out demand. One part of a  region may have storms while another has good  

weather. From east to west, the peak power demand  comes at different times. Some areas get sun,  

some get shade. But overall, demands average out  and become less volatile as the grid gets bigger  

geographically. Larger interconnections also  have more redundant paths for energy to flow,  

reducing the impacts of major equipment problems  like transmission line outages. They have more  

power plants, again creating redundancy and  making it easier to schedule offline time to  

maintain those facilities. And, the power plants  themselves can be bigger, taking advantage of the  

economies of scale to make energy less expensive  and more environmentally beneficial. Finally,  

larger areas have more resources. Maybe it’s  windy over here, so you can take advantage and  

build wind turbines. Maybe this area has lots  of natural gas production, so you can produce  

power efficiently without having to pay for  expensive fuel transportation. In general,  

a wide area interconnection allows the costs  of equipment, infrastructure, resources, and  

operations to be shared, making it easier to keep  things running reliably. Hawaii has none of that.

Roughly 75% of the electric power in the  state currently comes from power plants that  

run on petroleum. There are no oil or natural gas  reserves in Hawaii, which means the vast majority  

of power on the islands comes from fuel imported  from foreign countries. That makes the state very  

susceptible to factors outside of its control,  including international issues that affect the  

price of oil. Each island has only a handful  of major power plants and transmission lines.  

And when storms happen, they often hit the entire  place at once. It’s easy to see why retail energy  

costs in Hawaii are around 3 times the average  price paid across the US. Every increment of  

reliability costs more than the one before it, and  each island has no one else to share those costs  

with. So, they get passed down to consumers.  But, it’s not just that the grids are small.

The bulk of the remaining roughly 25% of Hawaii’s  electric power not produced in oil-fired power  

plants comes from renewable sources: wind,  solar, and a single geothermal plant. This  

has the obvious benefit of reducing CO2 emissions,  but it also reduces the state’s exposure to the  

complexities of the fuel supply chain and price  volatility, taking advantage of resources that are  

actually available on the islands. But, renewable  sources come with their own set of engineering  

challenges, particularly when they represent  such a large percentage of the energy portfolio.

Of course, renewable sources are intermittent.  You don’t get power when the wind doesn’t blow  

or the sun doesn’t shine. That sporadic  nature necessitates options for storage  

or firm baseload to make up the difference  between supply and demand. It also makes it  

more complicated to forecast the availability of  power to plan ahead for maintenance, fuel needs,  

and so on. And, it requires those storage  facilities or baseload plants to ramp down  

and up very quickly as the sun and wind come and  go. But that’s not all. Solar and wind sources  

are also considered “low-inertia”. Thermal  and hydroelectric power plants generally use  

enormous turbines to generate electricity. Those  big machines have a lot of rotational inertia that  

stabilizes the AC frequency. The frequency of the  alternating current on the grid is basically its  

heartbeat. It’s a measure of health, indicating  whether supply and demand are properly balanced.  

If frequency starts to deviate too much, equipment  on the grid will sense that something’s wrong and  

disconnect themselves to prevent damage. The same  is true for lots of industrial equipment and even  

consumer devices. When conditions on the grid  fluctuate - say a transmission line or generator  

suddenly trips offline - the rotational inertia in  those big spinning turbines can absorb the changes  

and help the grid ride through with a stable  frequency. Solar panels and most wind turbines  

connect to the grid through inverters. Instead of  heavy spinning machines creating the alternating  

current, they’re basically just a bunch of little  switches. That means disturbances can create a  

faster and more significant effect on the grid,  reducing the quality of power and making it more  

difficult to keep things stable. I’m planning a  deep dive into how inverter-based energy sources  

work, so stay tuned for that in a future video.  But, it gets even more complicated than that.

Of all the renewable energy on the Hawaiian  islands, about half currently comes from  

small-scale solar installations, like those on  residential and commercial rooftops. They’re  

collectively known as “distributed energy  resources.” This has the obvious benefit  

of bringing resources closer to the loads,  reducing strain on transmission lines. It also  

takes advantage of space that is already developed  and builds capacity on the grid without requiring  

the utility to invest in new facilities. But,  distributed sources come with tradeoffs. Most  

parts of the grid are built for power to flow  in one direction, so injecting electricity at  

the downstream end can create unexpected loads  on circuits and equipment not designed to handle  

it. Distributed sources also affect voltage and  frequency, since something as simple as a cloud  

passing over a neighborhood can dramatically swing  the flow of power on the network. The inverters on  

small solar installations are generally dumb.  And I’m using that as a technical term. They  

can’t communicate with the rest of the grid; they  only respond based on what they can measure at the  

point of connection. The grid operator doesn’t  get good data on how much power the distributed  

sources are putting into the grid, and they have  little control over those inverters. They can’t  

tell them to reduce power if there’s too much  on the grid already or increase power to provide  

support. And inverters, especially consumer-grade  equipment, can behave in unexpected and unintended  

ways during faults and disturbances,  magnifying small problems into larger ones.

Those inverters can also make the grid more  vulnerable to cyberattacks since their security  

depends on individual owners. It’s not hard to  imagine how someone nefarious could take advantage  

of a large number of distributed sources  to sabotage parts of the grid. And finally,  

distributed resources affect the revenue that  flows into the utility, and this can get pretty  

contentious. The rates a customer pays for  electricity cover a lot of different costs,  

many of which don’t really evaporate on a  kilowatt-per-kilowatt basis if you remove  

that demand from the grid. Fixed costs like  maintenance of infrastructure still come due,  

even if that infrastructure is being used at a  lower capacity on sunny days. With net metering,  

it gets even more complicated to figure out  how much that power injected into the grid is  

really saving, not to mention how those savings  should be distributed across the customer base.

And, these challenges are only becoming more  immediate. Hawaii’s Clean Energy Initiative,  

launched in 2008, set a goal of meeting  70 percent of its energy needs through  

renewables and increased efficiencies by 2030.  In 2014, they doubled down on the commitment,  

setting a goal of completely eliminating fossil  fuel use by 2045. That would take them from one  

of the most fossil-fuel-dependent states in  the US to the most energy-independent. And,  

they’ve taken some big steps toward that goal.  Renewable generation has gone from less than  

10% to about 25% of the total already, and a  host of policies have been changed to create  

more opportunities for renewables on the  grid. Solar water heaters are now required  

for most new homes. Rebates are available for  solar installations. The only coal-fired plant  

in the state was controversially shut down  in 2022. And, there is a big list of solar,  

battery storage, and biofuel turbine projects  expected to come online in the near future.

For better or worse, Hawaii has become a  full-scale test bed for renewables and the  

challenges involved as they become a larger and  larger part of the grid. Many consider natural gas  

to be a bridge fuel to renewables, a firm resource  that is generally cheaper, cleaner, and often more  

stable in price than other fossil fuels. But  Hawaii is hoping to leapfrog the bridge. For  

the climate and their own energy security, they’ve  gone all in on renewables, making them a leader in  

the world, but also forcing them to work out some  of the bugs that inevitably arise when there’s no  

one ahead of you to work them out first. There  are some really cool innovations on the horizon  

as Hawaii grows closer to its goal. Smart grid  technologies will add sensors and communications  

tools to automate fault detection, recovery,  and restoration, and enable power to flow more  

efficiently across distributed resources. Hawaiian  Electric is also testing out time-of-use rates to  

encourage customers to shift their power use to  off-peak hours, hopefully smoothing out demands  

and reducing the need for expensive generators  that only get used for a few hours per day.

That idea really underscores the significant  challenge Hawaii faces in keeping its grids  

operating. Improvements and capacity upgrades  help everyone, but they cost everyone too,  

and they cost more for every additional  increment of uptime. There’s no reliability menu,  

and kilowatt-hours don’t come a la carte.  If you’re a self-sufficient minimalist or  

frequent nomad who isn’t bothered by the idea  of intermittent power, you can’t pay a cheaper  

rate for less dependable service. And if you use  a powered medical device or work a high-powered,  

always-connected job at home, you can’t pay  extra for more reliability. In many ways,  

Hawaiians are all in it together.

Drawing that  line between what’s worth the investment and  

what’s just gilding the electric lily is tough  already with such a diverse array of needs  

and opinions. Doing it on such a small scale,  multiplied by several islands, and with such a  

quickly growing portfolio of renewable energy  sources only magnifies the challenge. But it  

also creates opportunities for some really cool  engineering to pave the way for a more resilient,  

secure, and flexible energy future, not just for  Hawaii, but hopefully all the rest of us too.

If there’s one thing I learned from researching  and talking to people for this video, it’s that  

Hawaiians care a lot about how their state  is portrayed in the media. There’s a lot of  

complexity in the history and culture, and it’s  easy to miss out on important context if you’re  

not from there, and I’m not. And that happens  a lot for me, actually, even for topics you  

think would be strictly about the science  and engineering. Here’s just one example:

The private Odysseus lander (kind of)  successfully landed on the moon a few  

weeks ago. There’s not a lot of politics in  a story like this, but if you look closely,  

you can see it through slightly different lenses.  More than 289 news outlets covered it. Of these  

289 news outlets, 35% lean left and 20% lean  right. And, while the headlines themselves are  

relatively similar across the political spectrum,  the articles themselves are a little different.  

Right-leaning news outlets tended to focus  on the private sector aspect of the mission,  

while left-leaning outlets ascribed more of the  achievement toward the partnership with NASA.

With today’s sponsor, Ground News, it’s  easy to pick out these little details  

and rise above the biases that are inherent  in lots of media sources. For every story,  

you get a quick visual breakdown of the political  biases, factuality ratings, and ownership of the  

sources. Everything’s in one place, so it’s easy  to compare multiple articles and make sure you  

have a well-rounded understanding of the story.  For the Odysseus story, 49% of the reporting  

outlets are owned by Media Conglomerates. One of  my favorite features is the Blindspot Feed, which  

shows you stories that are mostly reported by  one side of the political spectrum or the other.

I don’t think we’ll ever get  away from biases in reporting,  

but reading the same story from different  angles gives me context and insights that  

would be harder to come by just using my  typical sources. Ground News makes me feel  

more confident that I’m not living in a bubble  controlled by algorithms that only try to show  

me what I want to see. And they’re offering a  huge discount right now if you use my link in  

the description. Subscribe to get a more  transparent media landscape using my link  

ground dot news slash practicalengineering  for 30% off the Vantage subscription. That  

link is in the description. Thank you for  watching, and let me know what you think!