Solar panels in Kahului, HI
Roofs in Kahului get about 1,627 hours of usable sunlight a year — more than 61% of the cities we've measured. Here's what that means in cost, savings and payback, using real rooftop data rather than a national average.
Check your specific roof in Kahului → City averages are a starting point; your own roof's size, pitch and shading change the answer a lot.
What a typical Kahului solar system costs
A 20-panel system (8 kW) is about right for an average Kahului home using 10,800 kWh a year. It would produce roughly 11,064 kWh annually and offset 100% of that usage.
| System | Size | kWh/yr | Net cost | Saves/yr | Payback |
|---|---|---|---|---|---|
| 8 panels | 3.2 kW | 4,425 | $6,384 | $1,863 | 3.4 yrs |
| 12 panels | 4.8 kW | 6,638 | $9,576 | $2,795 | 3.4 yrs |
| 16 panels | 6.4 kW | 8,851 | $12,768 | $3,726 | 3.4 yrs |
| 20 panels | 8 kW | 11,064 | $15,960 | $4,575 | 3.5 yrs |
| 26 panels | 10.4 kW | 14,383 | $20,748 | $4,924 | 4.2 yrs |
Notice that payback barely improves as systems get bigger, and eventually gets worse. That's because you can only save money on electricity you were going to buy anyway. Once a system covers your usage, extra panels mostly generate exports at a much lower rate.
Why Kahului gets 1,627 sun hours
That figure comes from Google's analysis of real rooftops across Kahului — it already accounts for shading from trees, chimneys and neighbouring buildings, which is why it's lower than the raw "hours of daylight" figures you'll see elsewhere. An unusually open, unshaded roof in Kahului reaches about 1,694 hours, roughly 4% better than typical.
The numbers behind this page
| Typical usable sunlight | 1,627 hrs/yr |
|---|---|
| Unshaded roof | 1,694 hrs/yr |
| Electricity rate (Hawaii avg) | 42.1¢/kWh |
| Installed cost assumed | $2.85/W |
| Panel size assumed | 400 W |
| Federal tax credit | 30% |
| Typical household usage | 10,800 kWh/yr |
| Power used as generated | 34% |
| Paid for exported power | full retail (net metering) |
| Rooftops sampled here | 3 |
| Google imagery from | 2025 |
When Kahului actually produces
Annual totals hide the thing that catches people out: 29% of Kahului's yearly sunlight arrives in May–July, and just 19% across November–January.
| Month | Sun hrs | Share of year |
|---|---|---|
| Jan | 106 | |
| Feb | 122 | |
| Mar | 138 | |
| Apr | 152 | |
| May | 158 | |
| Jun | 159 | |
| Jul | 158 | |
| Aug | 154 | |
| Sep | 143 | |
| Oct | 126 | |
| Nov | 109 | |
| Dec | 101 |
Output is unusually steady — only about 1.6× between Jun and Dec. Kahului is close enough to the equator that seasonal variation is mild, which makes sizing a system considerably more predictable.
The annual total is measured from Google's rooftop imagery. Its split across months is calculated from solar geometry at Kahului's latitude, not separately measured, so treat the monthly figures as the shape of a typical year rather than a forecast.
How Kahului compares to the other 673 cities
| Measure | Kahului | Rank of 673 |
|---|---|---|
| Usable sunlight | 1,627 hrs | 263rd |
| Sunlight lost to shade | 4% | 456th most |
| Median roof size | 107 m² | 624th largest |
| Electricity rate | 42.1¢ | 3rd highest |
| Payback | 3.5 yrs | 3rd fastest |
| Grid carbon | 699 kg/MWh | 207th dirtiest |
What actually stands out about Kahului:
- Small roofs. The median Kahului roof is 107 m², smaller than 93% of cities measured — worth checking your own footprint before assuming a standard system fits.
- Expensive electricity works in your favour. At 42.1¢/kWh, Hawaii is among the priciest places to buy power — which is exactly what makes generating your own pay back faster.
Cities with almost the same sunlight
These are the closest matches to Kahului's 1,627 usable sun hours from other states and provinces. Same sunlight, different electricity prices — which is usually what decides whether solar is worth it.
| City | Sun hrs | Rate | Payback |
|---|---|---|---|
| Columbia, SC | 1,624 | 14.2¢ | 10.3 yrs |
| Boulder, CO | 1,624 | 14.8¢ | 9.9 yrs |
| Baton Rouge, LA | 1,631 | 12.1¢ | 12.1 yrs |
| Pasadena, TX | 1,631 | 15.1¢ | 9.7 yrs |
Nearby cities
See all of Hawaii → statewide sunlight, rates, incentives and every city we've measured.
Kahului solar questions
How many solar panels do I need in Kahului?
About 20 panels for an average home using 10,800 kWh a year. Kahului roofs get 1,627 usable sun hours, so each 400W panel produces roughly 553 kWh annually. A typical Kahului roof fits about 37 panels, so check your usable roof area before assuming that many will fit.
Is solar worth it in Kahului?
At 42.1¢/kWh and 1,627 sun hours, a typical system pays for itself in about 3.5 years and returns roughly $98,404 over a 25-year panel life. That is a solid return, and it improves further if electricity prices rise. Exported power earns full retail credit here.
How much do solar panels cost in Kahului?
A 8 kW system costs about $22,800 before incentives and $15,960 after the 30% federal tax credit. That works out near $2.85 per watt installed. Roof pitch, shading, electrical panel upgrades and equipment choice move the price most, which is why quotes for the same house can differ by thousands.
Worth reading before you buy
Estimates only, generated 2026-08-22 from Google Solar API rooftop samples and average Hawaii electricity rates. Not a quote and not financial advice. Your roof, usage, utility plan and local incentives will change these numbers — get real quotes before buying.