The Maui numbers, not the Oahu ones
Maui residential electricity averaged 41.58 cents per kWh in 2025 on Hawaiian Electric published figures, above the Oahu figure of 40.54. Smaller island grids carry higher per-unit costs, and Molokai at 48.48 and Lanai at 50.02 sit higher again.
A rate assumption a cent or two out does not sound like much, but it compounds across twenty-five years of a savings projection, and it compounds in the same direction as every other optimistic assumption in the model.
Ask which rate the projection used and where the figure came from. An installer quoting Maui from an Oahu template will usually not be able to answer that quickly.
Ask also whether the rate is held flat across the projection or escalated. An escalation assumption is defensible, but it should be stated rather than buried, because a generous one can carry most of the headline savings on its own.
The rules that do travel
The programme structure is statewide. New rooftop projects join Smart Renewable Energy on either the Export track, which provides export bill credits with no project size limit, or the Non-Export track, which does not permit export at all.
Customer Grid-Supply, Customer Grid-Supply Plus, Smart Export, Customer Self-Supply and the Standard Interconnection Agreement are closed to new customers on Maui exactly as they are on Oahu, and existing Customer Grid-Supply Plus and Smart Export customers transition to Smart Renewable Energy Export after seven years, with the earliest transitions having begun October 1, 2024.
The state RETITC under HRS Section 235-12.5 is a state credit and applies island-wide: 35 percent of actual cost capped at $5,000 per system, with a residential system defined as 5 kW of total output capacity.
Bring Your Own Device Plus is likewise a Hawaiian Electric programme rather than an Oahu one, paying $400 per kW of committed battery capacity with no maximum cap, doubled for low and moderate income households.
Storage, outages and honest expectations
A solar array on its own does not keep your lights on during an outage. Standard grid-tied inverters shut down when the grid goes down, for the safety of line workers, and that surprises homeowners more often than any other fact about solar.
Backup during an outage requires a battery and the right inverter and switching arrangement. If resilience is part of why you are considering solar in Kahului, it needs to be specified rather than assumed, and it should appear in the quote as equipment rather than as a promise.
Ask precisely which loads would be backed up and for how long. A whole-home backup and an essential-circuits backup are different systems at different prices, and the answer should be a circuit list rather than a reassurance.
BYOD+ is worth understanding alongside this, since it pays toward the battery but also commits you to exporting during a two-hour window each day for five years. Ask how the programme commitment interacts with holding charge in reserve for outages, because those two objectives are in tension.
Costing it out at Hawaii electricity prices
The 30 percent federal Residential Clean Energy Credit under Section 25D expired for property placed in service after December 31, 2025, so a cash or loan purchase in Kahului receives no federal tax credit. Section 48E survives at 30 percent for third-party owners under leases and power purchase agreements.
The state RETITC under HRS Section 235-12.5 remains at 35 percent of actual cost capped at $5,000 per 5 kW system, and BYOD+ pays $400 per kW of committed battery capacity, doubled for low and moderate income households.
Net metering is not available and neither are the five closed successor programmes, so the export assumption in any model has to come from the correct Smart Renewable Energy track.
Then add the Maui 2025 residential average of 41.58 cents per kWh, and check that the projection used the Maui figure rather than an Oahu or statewide one. Ask for the version in writing.