Possible, but the steep ground will be hard. The ground is steep, with slopes averaging about 21%. That raises the cost of a driveway, septic, and foundation. Rain is plentiful, about 52 inches a year. The growing season runs about 365 frost-free days, long enough for a spring and a fall garden.
What the land says
Rain
Rain can supply much of a household's water with a large tank. A garden mostly waters itself in normal years.
About 52 inches a year (University of Hawaii Rainfall Atlas)
Wells
Typical well depth. Budget for a mid-range well.
The typical well here is about 250 feet deep; a well typically runs $23,000 to $51,000
Growing season
Long enough for a spring and a fall garden.
About 365 frost-free days, USDA zone 12b; last frost about January 1, first about December 31
Sun
Good sun. Size the array and battery bank for winter.
About 5.2 hours of full sun a day, averaged over the year
Flood
Flood zones run along creeks and rivers here. Look up the parcel on FEMA's flood map.
FEMA maps flood zones within a quarter mile in places
Wildfire
Wildfire risk is high in places. Check the risk for the parcel you want.
U.S. Forest Service wildfire hazard map: Very Low to High here
Storms
Hurricanes and strong tornadoes are rare here.
NOAA: one hurricane-strength storm within 50 miles since 1975; no strong (EF2 or stronger) tornado within 25 miles since 1990
Terrain
Steep in places. Driveways, septic, and foundations cost more.
Slopes average about 21%, about 880 feet above sea level
Soil
Heavy clay. Expect a larger septic field, and work compost into garden beds. The county's soil test decides.
Silty clay, well drained (USDA soil survey). A standard system typically runs $5,000 to $10,000
Road
Paved roads are close by.
Nearest paved road usually within about 0.8 miles (OpenStreetMap)
Check a Hawaii parcel, or plan the one you own
Get a free 0-100 off-grid score.
A step-by-step build plan, sizing your solar, water, garden, septic, heat, and buildings.
Is it legal here?
Zoning
We found no public zoning map for Honolulu County, so call the county planning office with the parcel number to ask whether the land is zoned.
Building code
Hawaii has a statewide building code, with a residential code based on the 2018 International Residential Code. Each county adopts it with its own changes and enforces it through the county building department, so plan on a county building permit for a house.
Rainwater
Collecting it is allowed.
Composting toilets
Allowed with a permit and an approved unit.
Water rights
A mix of two systems. Ask the state water office before you drill a well or dam a creek.
Drilled to about 250 feet, with pump and pressure tank
Septic
$5,000 to $10,000
Standard system
Solar and batteries
$18,000 to $34,000
Sized for a modest household
Road or driveway
$6,000 to $17,000
From the nearest road to a house site
Clearing
$2,000 to $9,000
A house site, solar, and garden
Total
$55,000 to $121,000
Before the house
Before you make an offer on land here
Soil test
Get a soil test before you count on septic.
Clay drains slowly and can fail the test.
Zoning
Call the county planning office with the parcel number.
There is no public zoning map, so we cannot tell whether the land is zoned.
Wildfire
Ask an insurance agent whether they will write a policy.
The U.S. Forest Service rates wildfire risk high in places.
Nearby counties
989,408 people live in Honolulu County, about 1646.9 per square mile. It ranks 3rd of the 5 Hawaii counties we scored, and Hawaii ranks 36th of 50 states.