Hawaii has the highest residential electricity prices in the country, which makes the state’s Renewable Energy Technologies Income Tax Credit—universally called RETITC—one of the most lucrative state-level solar incentives any homeowner can claim. Codified under Hawaii Revised Statutes 235-12.5, the credit covers 35% of a photovoltaic system’s installed cost, with a $5,000 cap per system per parcel for single-family residential property.
Layer that on top of the federal 30% Residential Clean Energy Credit and the net effect can offset more than half the sticker price of a rooftop array. Yet many newcomers to the islands underclaim the benefit, miss the refundable election window, or file an incomplete Form N-342 that triggers a Department of Taxation notice months later.
This article walks through the statute, the per-system math, the two filing tracks, the interaction with federal credits, and the specific traps that catch second-system owners and short-term rental operators. Every dollar figure, statutory citation, and form line referenced here ties back to current Hawaii Department of Taxation guidance and HRS 235-12.5 as amended.
What the RETITC Actually Covers
The Renewable Energy Technologies Income Tax Credit was enacted in 1976 as a flat-percent credit for wind, biomass, and solar systems. Subsequent amendments in 2003 and 2009 narrowed the qualifying technologies to three categories: solar thermal (water heating), photovoltaic (electricity generation), and wind-powered systems. The 35% rate for solar electric arrays has been stable since 2009, even as the federal credit cycled through expirations and renewals.
The credit is administered by the Hawaii Department of Taxation under HRS 235-12.5 and codified procedurally in Hawaii Administrative Rules 18-235-12.5. Both individual and corporate taxpayers can claim it, including trusts and the beneficiaries of pass-through entities. Active rules apply to systems installed and placed in service on or after January 1, 2013, when the per-system cap structure took its current form.
The credit does not require Hawaii residency in the strict sense—any taxpayer with Hawaii-source income filing a Hawaii return can claim it for a qualifying system on Hawaii real property. Nonresident owners of a Hawaii rental property routinely claim RETITC against their Hawaii nonresident return.
What does not qualify
Standalone battery storage, smart inverters sold separately, solar attic fans, pool heating systems below thermal-output minimums, and any system financed through a third-party power purchase agreement are excluded. The taxpayer must own the system outright. Replacement panels for a previously credited array also do not generate a new credit—the original system has already been “placed in service.”
The 35% Rate and the $5,000 Per-System Cap
For photovoltaic systems, RETITC pays 35% of the actual installed cost of each system, capped at $5,000 per system per parcel for a single-family residential property. Multi-family residential properties cap at $350 per unit per system. Commercial properties cap at $500,000 per system. The credit applies to equipment, mounting hardware, inverters, wiring, permits, and labor—essentially the full installed cost less any third-party rebates received.
Because the cap binds at $5,000, a single-family system priced at or above $14,286 hits the ceiling. Anything above that point delivers no additional Hawaii credit dollars on that one system. A 6 kW rooftop install averaging $3.50 per installed watt prices out at $21,000, well over the binding threshold.
The federal 30% credit, by contrast, has no per-system dollar cap and continues scaling with system price. The two credits do not coordinate in a way that reduces one based on the other; both are computed against the same gross installed cost, subject to the basis-reduction rule discussed later for business-use property.
| Property Type | PV Cap per System | Solar Water Heater Cap | Wind Cap per System |
|---|---|---|---|
| Single-family residential | $5,000 | $2,250 | $1,500 |
| Multi-family residential (per unit) | $350 | $350 | $200 |
| Commercial | $500,000 | $250,000 | $500,000 |
| Alternative per-kW (water heating) | — | $500/kW | — |
Cost components that count toward the credit base
- Solar modules (panels) and their racking/mounting hardware
- String or microinverters and DC optimizers
- Disconnects, conduit, wiring, and combiner boxes
- Production meter and HECO-required upgrade equipment
- Roof reinforcement directly required for the array
- Permit fees, plan review fees, and electrical inspection charges
- Installation labor, design engineering, and project management
Third-party rebates—rare on Oahu since HECO’s CBRE program closed enrollment—must reduce the basis. Manufacturer rebates paid to the installer (passed through as a price reduction on the invoice) already reduce basis automatically. Cash discounts from the contractor never increase basis.
The Refundable vs Nonrefundable Election
Every PV claimant on Form N-342 must choose one of two tracks: nonrefundable (default) or refundable (elective). The election is irrevocable for that year’s credit and cannot be changed after the return is filed. Picking the wrong track is the single most common—and most expensive—mistake on a Hawaii solar return.
The nonrefundable track gives the full 35% credit, capped at $5,000, but it can only zero out Hawaii income tax liability. Any unused credit carries forward indefinitely until exhausted. A household with $2,800 of Hawaii tax liability would use $2,800 of credit and carry the remaining $2,200 to the next year.
The refundable track converts the credit into cash via the return, but at a 30% reduction. The maximum refundable amount equals 70% of what the nonrefundable credit would have been. So a $5,000 capped credit becomes a $3,500 refundable check if the election is made.
| Scenario | Gross Credit | Hawaii Tax Liability | Refundable Election Yields | Nonrefundable Yields This Year |
|---|---|---|---|---|
| High earner, high tax | $5,000 | $8,400 | $3,500 refund | $5,000 offset |
| Median household | $5,000 | $3,200 | $3,500 refund | $3,200 offset + $1,800 carryforward |
| Retiree, low Hawaii tax | $5,000 | $600 | $3,500 refund | $600 offset + $4,400 carryforward |
| Zero-tax filer | $5,000 | $0 | $3,500 refund | $0 this year, $5,000 carryforward |
The math favors refundability for retirees on fixed income, anyone with a heavy Hawaii itemized deduction load, and households with mortgage interest large enough to offset most of their Hawaii tax. For high-W2 earners with steady $7,000+ Hawaii tax bills, nonrefundable wins—they capture the full $5,000 in year one with no haircut. See how Hawaii taxes retirement income for the underlying liability mechanics.
Election timing and per-taxpayer scope
The election is made annually and applies to all systems claimed by a single taxpayer for that year. A household that owns both PV and solar water heating cannot mix elections between systems on the same return. Hawaii Department of Taxation tax information releases periodically clarify edge cases; consulting a Hawaii-licensed CPA before signing the return is prudent for any system above the $14,286 break-even point.
Solar Water Heaters: The Other RETITC Track
Solar water heating systems trigger the same 35% credit rate but face a much lower dollar cap. Single-family residences cap at $2,250 per system; multi-family at $350 per unit; commercial at $250,000 per system. Hawaii also publishes an alternative per-kilowatt cap of $500/kW for solar water heating, used when an installer rates the system by thermal output capacity rather than by dollar invoice—uncommon for residential, more typical in commercial procurement.
Solar water heating was effectively mandatory on new single-family construction in Hawaii from 2010 onward, except where written variance was granted. Most newer homes already have a system and the original builder claimed the credit. A retrofit replacing an electric tank can still qualify if no prior credit was claimed on that parcel for that technology.
A typical residential solar water heater on Oahu installs for $5,500 to $7,500 turnkey. At 35%, the credit math caps at $2,250 even on a $7,500 system, since 35% of that price is $2,625—above the cap. Households pairing a new PV array with a new solar water heater can claim both credits on separate N-342 forms.
Form N-342: Filing Mechanics Line by Line
Form N-342, “Renewable Energy Technologies Income Tax Credit,” is the primary claim form. Each separate system requires its own N-342—a household with rooftop PV plus a solar water heater files two forms. Partnerships, S corporations, estates, and trusts use Form N-342A to allocate the credit to partners, shareholders, or beneficiaries, who then file their personal N-342 with the allocation attached.
The form runs three pages. Page 1 identifies the system, the property, and the placed-in-service date. Page 2 computes the credit, including the 35% calculation and the per-system cap application. Page 3 handles the refundability election, signature block, and any carryforward from prior years.
The N-342B and N-342C supplements
Form N-342B is a worksheet for taxpayers claiming on a system 1,000 kW or larger—almost exclusively commercial. Form N-342C is the per-system itemization required when a single taxpayer claims credits on more than one system in the same year. Anyone with a PV system plus a solar water heater needs an N-342C.
Key line items that trip up filers include line 3 (total cost basis—must subtract rebates), line 7 (cap selection—the form makes the taxpayer pick the right cap from a list), and line 23 (the refundable election checkbox). Skipping the checkbox defaults the credit to nonrefundable, which is irreversible once filed.
Where the form attaches
- Individuals: attach N-342 (and any N-342C) to Form N-11 or N-15
- Corporations: attach to Form N-30 with a copy of the installer invoice
- Trusts and estates: attach to Form N-40 with N-342A allocations
- Partnerships and S corps: file N-342A at entity level, give K-1 with credit allocation to each owner
Multi-System Rules: What Counts as “One System”
A “system” for RETITC purposes is the combination of components installed under a single permit that share a common inverter or interconnection point. Adding panels to an existing array under a separate permit a year later generally constitutes a new system, eligible for its own $5,000 cap—but the Department of Taxation scrutinizes claims where the second system shares inverters or feeders with the first.
Two genuine separate systems on the same single-family parcel each get their own $5,000 cap. Common scenarios: a main-house rooftop PV plus a detached ADU or ohana unit with its own ground-mount array, or a main system installed in 2020 plus an expansion installed in 2025 under a new permit with new equipment.
The “per parcel” language matters for owners with multiple TMK-numbered lots. Two adjacent lots under separate Tax Map Key numbers each get their own caps even if owned by the same household. Owners of multi-parcel rural compounds in Volcano or Puna routinely structure installs across parcels to multiply caps. See the county property tax breakdown for how parcels are identified.
The “placed in service” timing rule
A system is placed in service when it is operationally ready to generate electricity to spec, with all utility approvals in hand. For grid-tied PV, that means HECO’s permission-to-operate letter is in place. Systems installed in late December but interconnected in January count for the following tax year, not the year the panels physically landed on the roof.
Stacking with the Federal 30% Investment Tax Credit
The federal Residential Clean Energy Credit pays 30% of installed cost with no dollar cap through 2032, stepping down to 26% in 2033 and 22% in 2034 under the Inflation Reduction Act schedule. The Hawaii RETITC stacks on top, producing some of the most attractive combined incentives in any U.S. state.
Hawaii does not require basis reduction for the federal credit on personal-use residential property—both credits are computed on the gross installed cost. For business-use property such as rentals or mixed-use, the federal credit reduces depreciable basis by 50% of the federal credit amount, and Hawaii follows the same treatment for the state credit.
| Installed Cost | Federal 30% Credit | Hawaii 35% (Capped $5,000) | Combined Out-of-Pocket Cost | Effective Discount |
|---|---|---|---|---|
| $12,000 | $3,600 | $4,200 | $4,200 | 65.0% |
| $18,000 | $5,400 | $5,000 (capped) | $7,600 | 57.8% |
| $25,000 | $7,500 | $5,000 (capped) | $12,500 | 50.0% |
| $35,000 | $10,500 | $5,000 (capped) | $19,500 | 44.3% |
| $50,000 | $15,000 | $5,000 (capped) | $30,000 | 40.0% |
Both credits attach to the year the system is placed in service. A single household claims both on the same year’s returns: federal Form 5695 plus Hawaii Form N-342. Carryforward rules differ—federal credit carries forward at full value, Hawaii nonrefundable carries forward at full value, Hawaii refundable election applies the 30% reduction in the placed-in-service year regardless of liability.
Special Situations: Rentals, ADUs, and Battery Storage
A photovoltaic system on a residential rental property qualifies for RETITC, but the credit lands on the owner’s Hawaii income tax return rather than the tenant’s. The owner reduces depreciable basis by the full state credit before computing MACRS depreciation. This basis-reduction step is where many investor-owners stumble, particularly out-of-state owners using mainland CPAs unfamiliar with HRS 235-12.5.
Short-term rental properties subject to the General Excise Tax and Transient Accommodations Tax can still claim RETITC. The system is depreciated as 5-year property under MACRS. The GET treatment of solar income is a separate question; a homeowner with surplus generation receiving HECO bill credits is not selling power for GET purposes.
ADUs and ohana units
A detached accessory dwelling with its own electrical service and PV array typically qualifies as a separate system on the same parcel, generating its own $5,000 cap. Attached ADUs sharing a single meter with the main house generally do not. Honolulu’s ADU permit rules govern the underlying construction; the credit follows the meter configuration, not the dwelling count.
Battery storage carve-outs
Standalone batteries are not eligible. Batteries installed simultaneously with a PV system, on the same permit and invoice, can be included in the PV system’s basis—subject to the same $5,000 cap. Households adding battery storage to an existing PV array a year later get no Hawaii credit on the battery, though the federal 30% credit covers it.
Real Electricity Costs That Drive the Math
Hawaii’s electricity rates make the credit economically pivotal in a way it would never be in Florida or Texas. Residential rates on Oahu have averaged $0.40 to $0.45 per kilowatt-hour for the past three years, more than three times the U.S. mainland average. Maui and Big Island rates run higher still. The EIA Hawaii electricity profile publishes the current data.
A typical Honolulu single-family home consuming 600 kWh per month spends roughly $260 to $290 on electricity. Annualized, that is $3,200 to $3,500 in baseline grid expense. A 6 kW rooftop PV offsetting 80% of that load delivers $2,500+ in annual savings, paying back the post-credit out-of-pocket investment in 4 to 6 years. The solar payback math page works through household scenarios in detail.
For perspective, the latest Honolulu CPI release shows energy commodities consistently outpacing mainland inflation. Locking in a 25-year levelized rate via owned solar is a hedge against that trajectory, and the RETITC is what makes the upfront math work for most households. The monthly cost-of-living breakdown shows electricity’s share of typical Hawaii budgets.
Common Pitfalls and Department of Taxation Audit Triggers
The most frequent N-342 issue is double-dipping on a system already credited by a prior owner. Hawaii’s audit screen cross-references TMK numbers against prior-year N-342 filings; a second claim on the same parcel for the same technology generates a desk audit letter within 90 days of filing.
The second most common issue is missing the refundable election checkbox on a return where refundability was clearly intended. The Department interprets the absence as a nonrefundable election, and no amended return cures it. Filers must verify line 23 (or its current line equivalent on revised forms) is checked before signing.
Third: claiming the credit on equipment that does not meet Hawaii’s minimum technology standards. Solar water heating systems must meet SRCC OG-300 certification. PV modules must be UL-listed and on the HECO-approved equipment list. An off-spec system that passed the building permit can still fail the tax-credit eligibility test.
- Mismatched placed-in-service dates between the federal return and N-342
- Missing or unreadable installer invoice copies
- Failure to file N-342C when claiming multiple systems
- Cost basis that includes ineligible items such as roof replacement or tree removal
- Refundable election on a capped credit without recalculating the 70% figure correctly
Investigative reporting by Honolulu Civil Beat and the Star-Advertiser over the past decade has tracked legislative tension around the credit’s fiscal cost, with the Department of Taxation reporting annual claims in the high tens of millions. The credit survives each legislative session despite recurring proposals to cap or reduce it.
Financing implications
A solar loan from a Hawaii credit union typically anticipates the federal and state credits as a balloon payment at month 18, requiring the borrower to apply the credits against principal once received. Borrowers who elect Hawaii refundability and take the 30% reduction should adjust the expected paydown accordingly. The credit union options for new Hawaii residents covers the relevant local lenders.
Other Hawaii Tax Credits That Pair With RETITC
Hawaii operates several other property-tied credits worth considering in the same year a household claims RETITC. The most significant is the Act 326 cesspool conversion credit, which pays up to $10,000 for replacing a cesspool with a septic or sewer connection on qualifying parcels. Households doing a major rural retrofit often stack RETITC, the cesspool credit, and the federal 30%.
The Important Agricultural Land Qualified Agricultural Cost credit, the Low-Income Household Renters Credit, and the Refundable Food/Excise Tax Credit all run on the same Hawaii return. None reduces or interacts with RETITC directly, but they may shift the math between refundable and nonrefundable elections by changing the total Hawaii tax liability for that year.
Frequently asked questions
Does the RETITC have an expiration date?
HRS 235-12.5 has no sunset clause for photovoltaic systems as of the 2026 tax year, unlike the federal credit which steps down in 2033 and 2034. The 35% rate and $5,000 per-system cap remain in statute until amended by the Hawaii Legislature. Bills have been introduced periodically to reduce or replace it, but none has passed.
Can the credit be claimed on a system purchased through a power purchase agreement?
No. RETITC requires that the taxpayer own the system outright. If a third party owns the panels and the homeowner pays a per-kWh PPA rate, the third party claims the credit—not the homeowner. Cash-paid systems and financed-but-owned systems both qualify; leased systems and PPAs do not.
What if a system is installed in December but not connected to the grid until January?
The credit attaches to the year the system is “placed in service,” not the year of purchase or installation. HECO’s interconnection approval letter is the standard proof of placed-in-service date. A December install with January 5 interconnection counts toward the next tax year’s return, not the prior year’s.
Are battery storage systems eligible for RETITC?
Standalone battery storage does not qualify under HRS 235-12.5—the statute lists photovoltaic, solar thermal, and wind only. Batteries integrated as part of a single PV installation can be included in the system’s basis if the invoice lists them as part of one bundled solar project. The federal 30% credit does cover standalone storage.
How does the credit interact with depreciation on a rental property?
For a system installed on a residential rental, owners reduce the depreciable basis by the full RETITC plus the federal credit before computing MACRS depreciation. The credit itself reduces basis under IRC §50(c); Hawaii follows this treatment. Failing to reduce basis is a common audit trigger on rental property returns where the credits are claimed.
What documentation should be retained?
Keep the signed installer contract, paid invoices showing the system cost, manufacturer specification sheets, the HECO interconnection approval letter, the building permit close-out, and proof of placed-in-service date. The Department of Taxation can request these for up to three years after the return is filed, or longer for a substantial understatement.
Can the credit be transferred or sold?
Hawaii’s RETITC is nontransferable—it stays with the taxpayer who paid for and placed the system in service. Unlike some federal energy credits introduced under the Inflation Reduction Act, RETITC has no transferability or direct-pay mechanism. If a home is sold mid-year, the seller (who installed) claims the credit, and the buyer claims nothing.