At 41.41% of residents reporting the ancestry, Aiea contains the largest concentration of persons of Japanese heritage in the United States.
Some residents of Aiea claim that their town is the only town in the world spelled entirely with vowels. This claim may or may not be valid, depending on whether or not one regards the okina to be part of the name "Aiea". Because the okina is considered a consonant in the Hawaiian language, this claim is technically incorrect. However, when people outside of Hawaii speak of Aiea, the okina is typically omitted. In this context, the claim that Aiea is spelled only with vowels is true. However, there are many other towns in the world spelled with only vowels, including but not limited to Ea, Spain and Aue in Germany, several towns in Norway and Sweden named Å, and a village, forest and valley in Scotland called Ae. There is also a village named Y in France.
The U.S. postal code for Aiea is 96701.
Kamehameha Highway (Hawaii Route 90) divides most of Aiea from the shore of Pearl Harbor (mostly US government property), and the parallel major thoroughfare, Interstate H-1, further cuts the town's commercial district into two distinct areas. These east-west routes (and other streets, such as Moanalua Road) connect Aiea to Pearl City immediately adjacent on the west and Hālawa adjacent on the east. The residential area known as Aiea Heights extends up the ridgeline above the town. The communities of Newtown Estates and Royal Summit are located at the western edge of Aiea near its border with Pearl City at Kaahumanu Street. Residents of the census-designated places (CDP) of Waimalu and Hālawa use Aiea in their postal address.
As Aiea has several miles of shoreline on Pearl Harbor, the focus of the 7 December 1941 attack by the Japanese on military installations there greatly impacted the town. For example, one damaged ship, the USS Vestal, beached at Aiea Bay to prevent sinking. Many photographers photographed the battle from the hills in Aiea.
After World War II the plantation shut down and the mill was converted into a sugar refinery. Meanwhile, developers started extending the town into the surrounding former sugar cane fields. In the years since then, Aiea has grown into an important suburb of Honolulu. The town's sugar history came to a close in 1996, when C&H Sugar closed the refinery. Then in 1998, the 99-year old sugar mill was torn down by the owners, amid protests from town residents and the County government.
There were 2,758 households out of which 27.3% had children under the age of 18 living with them, 63.0% were married couples living together, 13.3% had a female householder with no husband present, and 18.1% were non-families. 13.9% of all households were made up of individuals and 7.7% had someone living alone who was 65 years of age or older. The average household size was 3.24 and the average family size was 3.51.
In the CDP the population was spread out with 21.2% under the age of 18, 6.4% from 18 to 24, 27.6% from 25 to 44, 23.1% from 45 to 64, and 21.7% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 96.3 males. For every 100 females age 18 and over, there were 96.0 males.
The median income for a household in the CDP was $71,155, and the median income for a family was $75,992. Males had a median income of $41,384 versus $32,394 for females. The per capita income for the CDP was $25,111. 4.6% of the population and 3.4% of families were below the poverty line. Out of the total population, 8.1% of those under the age of 18 and 4.0% of those 65 and older were living below the poverty line.