Plain-language definitions for every term you'll encounter when going solar in Hawaii — from AC coupling to utility rates. Built from 33 years of installation experience on Oahu.
This glossary covers solar, battery storage, electrical, air conditioning, HECO programs, and financing terminology. We wrote each definition the way we'd explain it during a site visit — practical, specific, and grounded in what actually matters for Hawaii homeowners. Use the letter links below to jump to any section.
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A battery storage configuration where the battery has its own inverter and connects to the home's AC electrical panel, separate from the solar inverter. AC-coupled systems are common for battery retrofits on existing solar installations because you don't need to replace or modify the original solar equipment. The Tesla Powerwall is the most common AC-coupled battery we install in Hawaii. The trade-off versus DC-coupled is a small efficiency loss from the extra DC-to-AC conversion step — typically 2-5%.
The type of electrical current used in your home's wiring and delivered by HECO's grid. Solar panels produce direct current (DC), which must be converted to AC by an inverter before your home can use it. Every appliance plugged into a wall outlet runs on AC power at 120V or 240V.
A unit measuring the flow rate of electrical current. Your home's electrical panel has a rated amperage — typically 200 amps for modern Hawaii homes. When we design a solar system, the panel's amp capacity determines how much equipment we can connect. Older homes with 100-amp panels sometimes need a panel upgrade before solar installation.
The compass direction a solar panel faces, measured in degrees from north. In Hawaii, south-facing panels (180° azimuth) produce the most annual energy, but west-facing panels (270°) can be strategically valuable because they generate more during HECO's late-afternoon peak rate window. We factor azimuth into every system design because it directly affects both production and the financial return from time-of-use export programs.
Everything in a solar installation besides the panels and inverter: racking, wiring, conduit, junction boxes, disconnects, monitoring hardware, and mounting hardware. BOS typically accounts for 15-25% of total system cost. In Hawaii, BOS specifications matter more than on the mainland because salt air corrosion demands marine-grade or stainless steel components, especially for homes within a mile of the coast.
The minimum amount of electricity your home draws around the clock — refrigerator, router, security system, standby loads. Knowing your baseload helps us size a battery system correctly. A typical Oahu home has a baseload between 300W and 700W, which means even at 2am your house is pulling power.
One complete charge and discharge of a battery. Battery warranties are measured in both years and cycles — the Tesla Powerwall 3 is warrantied for 10 years or an unlimited number of cycles, whichever comes first. In Hawaii, batteries typically cycle once per day (charge from solar during the day, discharge in the evening), so annual cycle count is roughly 365.
A unit of heat energy used to rate air conditioning and solar hot water systems. One BTU is the energy needed to raise one pound of water by one degree Fahrenheit. A typical window AC unit is rated at 8,000-12,000 BTU/hr; a whole-house mini-split system might be 36,000 BTU/hr. When we size AC systems in Hawaii, the BTU rating needs to match the home's cooling load — oversizing wastes energy and money.
Bring Your Own Device Plus — a HECO battery incentive program that pays you for installing a qualifying battery system and allowing HECO to dispatch it during grid emergencies. You receive an upfront capacity payment (currently around $400/kW) plus ongoing monthly performance credits for five years. The battery must meet minimum capacity and dispatch requirements. This is one of the strongest battery incentives in the country, and it stacks with the federal tax credit.
The maximum amount of energy a battery can store, measured in kilowatt-hours (kWh). The Tesla Powerwall 3 has a usable capacity of 13.5 kWh. Don't confuse capacity (total energy stored) with power (how fast it can deliver that energy). A battery with 13.5 kWh of capacity and 11.5 kW of power output can run a lot of loads simultaneously but will deplete faster under heavy draw.
Energy lost when solar panels produce more DC power than the inverter can convert to AC. This happens when panels are intentionally oversized relative to the inverter (a common design choice called DC oversizing). A small amount of clipping — typically 1-3% annually — is acceptable and often economically optimal because it means the inverter runs at full capacity for more hours of the day. Excessive clipping above 5% usually means the system was poorly designed.
A metal used in some lithium-ion battery chemistries (NMC). The industry trend, especially for home storage, is away from cobalt toward lithium iron phosphate (LFP) chemistry, which is safer, longer-lasting, and doesn't rely on ethically problematic mining. Both the Tesla Powerwall 3 and Enphase IQ Battery use LFP cells.
The protective tubing that houses electrical wiring between solar panels, inverters, and your electrical panel. NEC code requires specific conduit types and fill ratios. In Hawaii, we use UV-resistant and corrosion-resistant conduit because standard materials degrade quickly under tropical sun and salt exposure. Clean conduit runs are also an aesthetic consideration — nobody wants visible pipes zigzagging across their roof.
Mesh screening installed around the perimeter of rooftop solar panels to prevent birds, rats, and other animals from nesting underneath. In Hawaii, mynah birds and pigeons are the main offenders. Nesting debris can create fire hazards, attract pests, and interfere with wiring. We recommend critter guards on most installations, especially in neighborhoods near open fields or gulches.
A battery storage configuration where the battery connects directly to the solar panels' DC output before the inverter. DC-coupled systems are slightly more efficient than AC-coupled because energy only goes through one DC-to-AC conversion instead of two. They're the standard choice for new solar-plus-battery installations. The trade-off: you can't easily add a DC-coupled battery to an existing solar system without replacing the inverter.
Module-level power electronics (from SolarEdge, for example) that attach to each panel and perform maximum power point tracking at the panel level before sending DC to a central string inverter. They offer some of the per-panel optimization benefits of microinverters while still using a centralized inverter for the DC-to-AC conversion. Less common in new Hawaii residential installs, where Enphase microinverters dominate.
The gradual decline in a solar panel's power output over time. All panels degrade — the question is how fast. Premium panels like REC Alpha Pure-R degrade at roughly 0.25% per year, meaning after 25 years they're still producing above 93% of original capacity. Budget panels can degrade at 0.5-0.7% annually. In Hawaii, salt air and high UV exposure can accelerate degradation on panels with inferior encapsulant materials, which is one reason we're selective about the brands we install. See our solar guide for more on panel selection.
A charge on commercial electric bills based on the highest rate of electricity consumption (peak demand in kW) during a billing period, not just total energy used. Demand charges are a major cost driver for commercial properties in Hawaii. A business that briefly spikes to 50 kW of demand — even for 15 minutes — pays for that peak all month. Battery storage can shave these peaks and significantly reduce commercial bills.
The percentage of a battery's total capacity that can be used before recharging. Modern LFP batteries like the Powerwall typically allow 100% DoD, meaning you can use the full rated capacity. Older battery chemistries required keeping 10-20% in reserve to avoid damage, so a "10 kWh" battery might only deliver 8 kWh of usable energy.
A multiplier that accounts for real-world energy losses in a solar system — heat, wiring resistance, inverter efficiency, soiling, shading, and panel mismatch. A typical derate factor is 0.80 to 0.85, meaning a system rated at 10 kW under lab conditions will actually produce 8.0 to 8.5 kW under field conditions. In Hawaii, high ambient temperatures increase thermal derating, but our strong, consistent irradiance compensates. We use site-specific derate factors, not generic national averages.
The type of electrical current produced by solar panels and stored in batteries. DC flows in one direction, unlike alternating current (AC). An inverter converts DC to AC so your home can use the energy. Some modern appliances and EV chargers can use DC directly, which is more efficient but less common in residential applications.
The time period during which HECO can call on your battery to export stored energy to the grid under programs like BYOD+. The typical dispatch window is 6:00 PM to 8:30 PM, when grid demand peaks and solar production drops off. During a dispatch event, your battery feeds the grid instead of your home, which is why system sizing should account for both your evening usage and dispatch obligations.
The Database of State Incentives for Renewables & Efficiency, maintained by NC State University. It's the most comprehensive, up-to-date source for solar incentives, tax credits, and rebate programs by state. We reference DSIRE when helping customers understand which federal and state incentives apply to their installation.
The percentage of sunlight hitting a solar panel that gets converted to electricity. Premium residential panels today hit 22-24% efficiency. Higher efficiency means more power per square foot of roof space, which matters in Hawaii where many homes have limited roof area due to hip roofs, dormers, or shading from mature trees. The REC Alpha Pure-R panels we install run at about 22.3% efficiency.
The metal box where your home's main electrical circuits originate, usually in the garage or on an exterior wall. Solar systems, batteries, and EV chargers all connect here. Older Hawaii homes sometimes have undersized panels (100A or 125A) that need upgrading to accommodate solar and battery equipment. An electrical panel upgrade adds $1,500 to $3,000 to a project but is non-negotiable when code requires it.
The degree to which a home generates and stores enough energy to meet its own needs without relying on the utility grid. True 100% energy independence (off-grid) is rare and expensive on Oahu, but a well-designed solar-plus-battery system can cover 80-95% of a household's energy needs. For most Hawaii homeowners, the practical goal isn't going fully off-grid — it's reducing grid dependence enough that your monthly HECO bill drops to the minimum customer charge.
The cloud-based monitoring platform for Enphase microinverter systems. Enlighten shows real-time and historical production data for each individual panel, system-level performance, and energy consumption if a consumption monitoring CT is installed. It's available as a web app and mobile app. We set up Enlighten access for every Enphase system we install so homeowners can track their production and spot issues early.
The credit you receive on your HECO bill for solar energy sent to the grid. The credit rate depends on which program you're enrolled in — NEM, NEM+, Smart Export, or CGS+ — and can range from roughly $0.10/kWh to $0.33/kWh depending on time of day and program. Under Smart Export, exporting during the 5-9 PM peak window earns the highest credit, which is the primary financial argument for battery storage in Hawaii.
Electric Vehicle Supply Equipment — the charging station installed at your home for an electric car. Level 2 chargers (240V) are the standard for home installation and can fully charge most EVs overnight. Pairing an EV charger with solar means you're driving on sunshine instead of gasoline. In Hawaii, where gas prices regularly exceed $4.50/gallon, the savings are substantial.
The federal solar tax credit, currently at 30% of total system cost including equipment, labor, permits, and battery storage. This is a dollar-for-dollar reduction in your federal income tax liability, not a deduction. If your system costs $35,000, you get $10,500 off your federal taxes. The ITC applies to both solar and battery storage installed together or separately. See our incentives page for current details and how to claim it.
The most common type of solar hot water collector, consisting of a dark absorber plate inside an insulated, glazed box. Water or heat-transfer fluid flows through tubes bonded to the absorber and heats up. Flat-plate collectors are simple, reliable, and well-suited to Hawaii's climate. They've been standard on the islands for decades — you'll see them on rooftops across Oahu, from Kahala to Wahiawa.
Waterproof metal pieces installed where solar panel mounting bolts penetrate the roof surface. Proper flashing is critical to preventing leaks. In Hawaii's heavy rain conditions — Manoa gets over 150 inches a year — flashing quality separates good installers from bad ones. We use aluminum flashing with butyl sealant, and every penetration gets a visual inspection before panels go on top.
The hardware component that manages the connection between a Tesla Powerwall system, the home's electrical panel, and the utility grid. The Gateway handles automatic switching between grid power and battery backup during outages (islanding), monitors energy flow, and communicates with the Tesla app. It's the brain of a Powerwall installation.
A solar system connected to the utility grid (HECO in Hawaii). The vast majority of residential solar installations on Oahu are grid-tied, which allows you to export excess energy for credits and draw from the grid when solar production is insufficient. Grid-tied systems without a battery shut down during power outages for safety reasons — a fact that surprises many homeowners. Adding a battery allows a grid-tied system to operate during outages.
A solar array installed on a ground-based racking structure rather than on the roof. Ground mounts are used when the roof is unsuitable (wrong orientation, too much shade, structural concerns, or an older roof that needs replacement). They allow optimal panel tilt and azimuth and are easier to maintain and clean. The downside is they require yard space and typically cost more due to the foundation and racking. On Oahu, ground mounts are more common on larger properties in areas like North Shore or Windward side.
The state's ratepayer-funded energy efficiency program, administered as a public benefit program. Hawaii Energy offers rebates on energy-efficient appliances, including mini-splits, heat pump water heaters, and weatherization improvements. They also run rebate programs for solar hot water systems. Not the same entity as HECO — Hawaii Energy focuses on conservation and efficiency, while HECO is the electric utility.
Hawaiian Electric Company, the electric utility serving Oahu, Maui County, and Hawaii Island. HECO sets the rates, manages the grid, approves solar interconnections, and administers programs like NEM, Smart Export, and BYOD+. Every grid-tied solar installation in their service territory requires HECO approval before you can flip the switch. Understanding HECO's programs and rate structures is essential to maximizing the financial return on a solar investment.
A device that moves heat from one place to another instead of generating it directly. Air-source heat pumps are used in mini-split AC systems (moving heat out of your house) and heat pump water heaters (moving heat into your water tank). Heat pumps are 2-4 times more efficient than resistance heating, which is why heat pump water heaters qualify for both federal tax credits and Hawaii Energy rebates.
An advanced solar cell architecture that combines crystalline silicon with thin-film amorphous silicon layers. HJT cells have excellent temperature coefficients, meaning they lose less efficiency in hot conditions — a meaningful advantage in Hawaii's climate. They also have lower degradation rates and perform better in low-light conditions. REC's Alpha series uses HJT technology, which is one of the reasons we selected them as our primary panel.
The formal process of connecting a solar system to HECO's electrical grid. Interconnection requires an application, technical review, meter installation, and final approval. The timeline varies but typically takes 2-6 weeks after installation is complete. You cannot legally operate a grid-tied solar system or receive export credits until HECO grants interconnection approval and issues your Permit to Operate.
The device that converts direct current (DC) from solar panels into alternating current (AC) that your home uses. The inverter is the hardest-working component in a solar system and often the first to need replacement, typically lasting 12-25 years depending on type and quality. The three main types are string inverters, microinverters, and hybrid (battery) inverters. For most Hawaii residential installations, we use Enphase microinverters. See our solar page for equipment details.
Enphase's current-generation microinverter, used in most of our residential solar installations. The IQ8 series includes several models (IQ8M, IQ8A, IQ8H, IQ8HC) matched to different panel wattages. Key features include panel-level optimization, built-in rapid shutdown compliance, and the ability to produce limited solar power during grid outages even without a battery (Sunlight Backup). The IQ8's 25-year warranty matches the panel warranty, which eliminates the mid-life inverter replacement that string inverter systems typically require.
The power of sunlight hitting a surface, measured in watts per square meter (W/m²). Standard Test Conditions (STC) rate panels at 1,000 W/m². Hawaii receives some of the highest solar irradiance in the United States, which is why systems here produce more energy per installed kW than nearly any other state. Irradiance data drives the production estimates in our solar calculator.
When a solar-plus-battery system disconnects from the utility grid and operates independently, powering the home from solar and battery alone. Islanding happens automatically during power outages if you have a battery with a transfer switch (like the Tesla Gateway). Anti-islanding protection is required by code to prevent solar systems without batteries from backfeeding a dead grid, which would endanger utility workers.
An enclosed electrical box where wire connections are made and protected. In solar installations, junction boxes appear on the back of each panel (where the cell strings connect to output wires) and at various points in the system wiring. Proper junction box sealing is important in Hawaii to prevent moisture intrusion from humidity and rain.
A unit of electrical power equal to 1,000 watts. Solar system size is measured in kW (or kWDC for the panel rating). A typical Oahu residential system is 6-12 kW. Think of kW as the speedometer — it tells you how fast energy is being produced or consumed at any given moment. A 10 kW system at peak production is generating 10 kW of power. Your HECO bill, however, is based on kWh — see the next entry.
A unit of energy equal to one kilowatt of power used for one hour. This is what HECO charges you for — at roughly $0.41/kWh on Oahu as of early 2026. The average Oahu household uses 500-900 kWh per month. If kW is the speedometer, kWh is the odometer — it measures the total distance traveled. Battery capacity is also measured in kWh: a 13.5 kWh Powerwall stores enough energy to run a typical home for 6-10 hours without solar input.
A lithium-ion battery chemistry (also written as LiFePO4) used in most modern home batteries, including the Tesla Powerwall 3 and Enphase IQ Battery. LFP is safer than older NMC chemistry — it's more thermally stable and virtually eliminates the risk of thermal runaway (battery fire). LFP batteries also last longer (4,000-6,000 cycles) and don't use cobalt. The trade-off is slightly lower energy density, meaning LFP batteries are a bit larger and heavier for the same capacity. For stationary home storage, that trade-off is a no-brainer.
A graph or dataset showing how your electricity consumption varies throughout the day and across seasons. Your load profile determines optimal system size, battery strategy, and which HECO program makes the most financial sense. A home with high daytime usage (working from home, running AC all day) has a different optimal design than a home where everyone's gone until 5 PM. We analyze load profiles using 12-24 months of HECO billing data.
Using a battery to store cheap or free solar energy during the day and discharge it during expensive peak rate hours in the evening. Load shifting is the primary economic strategy behind residential battery storage in Hawaii. By shifting 10-15 kWh of daily consumption from peak to off-peak, a homeowner can save $80-$150 per month on HECO rates alone, before counting any export credits.
A federal tax depreciation schedule that allows commercial solar system owners to depreciate the cost of their system over 5 years (with bonus depreciation available). MACRS doesn't apply to residential systems, but for businesses, it's a massive additional incentive on top of the 30% ITC. A commercial system can recover 50-60% of its cost through combined tax benefits in the first year. Details on our incentives page.
A small inverter installed directly on (or next to) each individual solar panel, converting DC to AC at the panel level. Microinverters offer panel-level optimization, meaning shade on one panel doesn't drag down the whole array. They also provide panel-level monitoring and inherently comply with rapid shutdown requirements. Enphase microinverters are the dominant technology in Hawaii residential solar. Their main advantage over string inverters: no single point of failure, plus a 25-year warranty that matches the panels.
A ductless air conditioning system consisting of an outdoor compressor unit and one or more indoor wall-mounted heads. Mini-splits are the most energy-efficient way to cool a Hawaii home, consuming 30-50% less electricity than window units. They're quieter, more controllable (zone by zone), and pair exceptionally well with solar because you can run them during peak solar production for essentially free cooling. A single-zone mini-split typically draws 500-1,200 watts.
The industry term for a solar panel. A module consists of solar cells wired together, sandwiched between glass and backsheet, and framed in aluminum. Modern residential modules range from 400-450 watts. We use the terms "module" and "panel" interchangeably in customer conversations, but you'll see "module" on permits, spec sheets, and HECO applications.
Software that tracks your solar system's energy production, consumption, and battery status in real time. Most modern systems include monitoring via a phone app — Enphase Enlighten or the Tesla app, depending on your equipment. Monitoring lets you verify your system is performing as expected, catch issues early, and optimize your energy usage patterns. We set up monitoring for every system we install.
An algorithm used by inverters and charge controllers to extract the maximum possible power from solar panels as conditions change throughout the day. As sunlight intensity and temperature fluctuate, the optimal voltage-current combination shifts. MPPT continuously adjusts to find that sweet spot. Microinverters perform MPPT at each individual panel, while string inverters do it for the whole string — which is why microinverters handle partial shading better.
The North American Board of Certified Energy Practitioners — the gold standard certification for solar installers. A NABCEP-certified installer has passed rigorous exams covering system design, installation, and code compliance. When vetting a solar company, asking whether they employ NABCEP-certified professionals is one of the best indicators of technical competence. It's the difference between a company that follows best practices and one that wings it.
The set of electrical safety standards (NFPA 70) that governs how solar systems, batteries, and all electrical work must be installed. Hawaii adopts the NEC with local amendments. The 2023 NEC introduced significant changes for solar and battery installations, including rapid shutdown requirements and energy storage safety rules. Every AEI installation is designed and inspected to current NEC standards.
The original and most favorable HECO solar program, which credited exported solar energy at the full retail electricity rate. NEM is closed to new applicants — it reached its enrollment cap years ago. If you have NEM, you're grandfathered in and it's extremely valuable. Homes with NEM agreements that sell should understand that NEM status may or may not transfer to the new owner depending on the specific agreement terms. Current alternatives include Smart Export and BYOD+.
The general concept of measuring the difference between electricity consumed from the grid and electricity exported to the grid. When your solar system produces more than your home uses, the excess flows to the grid and your meter effectively runs backward (or you receive a credit). The specific terms and credit rates depend on which HECO program you're enrolled in. True 1:1 net metering (full retail credit) is only available under the legacy NEM program.
A solar system with no connection to the utility grid whatsoever. The home relies entirely on solar production and battery storage. Off-grid systems require significantly more panels and battery capacity to handle cloudy days and nighttime loads, plus a backup generator for extended low-production periods. On Oahu, going fully off-grid is rarely cost-effective because HECO grid access provides a safety net that's hard to replicate with batteries alone. Off-grid makes more sense for remote properties on Hawaii Island or Maui.
The unit of electrical resistance. Higher resistance in wiring means more energy lost as heat. That's why proper wire sizing (gauge) matters in solar installations — undersized wires lose energy and create safety hazards. Voltage drop calculations, which are essentially resistance math, determine the minimum wire gauge for every run in a solar system.
See DC Optimizers.
The number of hours per day when solar irradiance averages 1,000 W/m². It's a way to express total daily solar energy in a simple number. Oahu averages 5.0-5.5 peak sun hours per day annually, among the highest in the nation. A 10 kW system in a location with 5.2 PSH and an 82% derate factor produces roughly 10 × 5.2 × 0.82 = 42.6 kWh per day. Peak sun hours vary by roof orientation and shading — south-facing panels see more than north-facing ones.
The official authorization from HECO allowing you to turn on your grid-tied solar system and begin receiving export credits. PTO is issued after your system passes HECO's interconnection review, the production meter is installed, and all permits are cleared. Until PTO, you technically cannot operate your system (or you can in some cases but won't receive credits). The PTO timeline is one of the most common sources of customer frustration — it can take 2-8 weeks after physical installation is complete.
The technology of converting sunlight directly into electricity using semiconductor materials. A photovoltaic cell is the basic building block; cells are wired together to form modules (panels); modules are combined into arrays. The photovoltaic effect was discovered in 1839, but it took until the 2000s for the economics to make residential PV viable. In Hawaii, with electricity at $0.41/kWh, PV has been the single best home investment for over a decade.
A financing arrangement where a third-party company installs solar on your roof and sells you the electricity at a fixed rate, typically lower than HECO's rate. You don't own the system — the PPA company does. PPAs can make sense for homeowners who can't use the tax credits (low tax liability) or don't want the upfront cost. The downside: you capture less of the total savings, and PPAs can complicate home sales. We generally recommend owning your system if you can, because the long-term economics are significantly better.
Tesla's residential battery storage product. The current model, Powerwall 3, provides 13.5 kWh of usable capacity with an integrated solar inverter and 11.5 kW of continuous power output. Powerwalls are AC-coupled when added to existing solar systems or can be DC-coupled in new installations using the built-in inverter. We've installed thousands of Powerwalls across Oahu. They're reliable, well-supported by Tesla's software updates, and qualify for both the federal ITC and HECO's BYOD+ program.
A meter installed by HECO (or the solar company) that measures the total energy produced by your solar system, separate from the main utility meter that tracks net consumption. Production meter data is used for HECO program crediting, renewable energy certificate (REC) tracking, and performance monitoring. HECO requires a production meter for all interconnected solar systems.
The mounting system that secures solar panels to a roof or ground structure. Racking must withstand Hawaii's wind loads (rated for hurricane conditions in many jurisdictions), resist corrosion from salt air, and maintain watertight roof penetrations. The racking system is where cheap installations cut corners — and where problems show up five years later. We use IronRidge racking with stainless steel hardware for coastal installations.
An NEC safety requirement that solar panel voltage drop to safe levels (under 80V) within 30 seconds of the system being shut down. This protects firefighters and first responders who may need to work near or on a roof with solar panels. Enphase microinverters comply with rapid shutdown inherently — each panel has its own inverter that shuts down independently. String inverter systems require additional rapid shutdown devices at each panel to meet code.
A tradable certificate representing the environmental attributes of 1 MWh (1,000 kWh) of renewable energy generation. When your solar system produces electricity, it creates RECs that can technically be sold separately from the electricity itself. In residential applications, RECs are mostly relevant for utilities meeting renewable portfolio standards. Not to be confused with REC Group — the solar panel manufacturer.
A leading European solar panel manufacturer known for high efficiency, low degradation, and strong warranties. REC's Alpha Pure-R series uses HJT cell technology and is our primary panel choice for Hawaii installations. Key specs include 22%+ efficiency, 0.25% annual degradation, and a 25-year product and performance warranty. REC panels also carry a salt-mist corrosion certification (IEC 61701), which matters on an island. See our solar page for more on why we chose REC.
An evaluation of your roof's condition, orientation, pitch, material, structural capacity, and remaining lifespan to determine solar suitability. We conduct a roof assessment at every site visit. If a roof needs replacement within 5-10 years, we recommend doing the roofing work first — removing and reinstalling solar panels costs $3,000-$5,000 and disrupts your production.
Seasonal Energy Efficiency Ratio — the standard measure of air conditioning efficiency. Higher SEER means less electricity per unit of cooling. As of 2023, the industry transitioned to SEER2, which uses a slightly different testing method (results are about 4-5% lower than SEER for the same unit). In Hawaii, we recommend mini-splits with SEER2 ratings of 17 or higher. Our AC sizing tool helps match the right efficiency rating to your space and budget.
The percentage of your solar production that your home uses directly, rather than exporting to the grid. Higher self-consumption means greater savings, because the value of avoiding a $0.41/kWh HECO charge is always higher than the export credit you'd receive. Battery storage dramatically increases self-consumption — from a typical 30-40% without a battery to 70-90% with one. Running high-draw appliances (dishwasher, laundry, mini-split) during peak solar hours is the simplest way to boost self-consumption without a battery.
A site-specific assessment of how shadows from trees, buildings, and other obstructions affect solar panel production throughout the year. We use satellite imagery and on-site measurements to model shading impact hour by hour, month by month. Even small amounts of shading can significantly reduce production on string inverter systems — less so with microinverters, which optimize each panel independently. Mature monkeypod and banyan trees are the most common shading obstacles we encounter on Oahu.
A current HECO program that pays higher export credits during peak demand hours (roughly 5-9 PM) and lower credits during midday. Smart Export is designed to incentivize battery storage: charge your battery from solar during the day, then export during the peak window at premium rates. The peak export credit is significantly higher than the midday rate, which is why Smart Export paired with a battery consistently outperforms solar-only economics in Hawaii.
The accumulation of dirt, dust, pollen, bird droppings, or salt residue on solar panel surfaces, reducing light absorption and energy production. In Hawaii, soiling losses are typically 2-5% annually but can be higher near agricultural areas (red dirt), construction zones, or the coast (salt spray). Regular panel cleaning recovers this lost production. We recommend cleaning at least once or twice a year for most Oahu locations.
The percentage of a home's total hot water energy that comes from solar rather than the backup electric element. A well-designed solar hot water system in Hawaii achieves a solar fraction of 85-95%, meaning the electric backup only kicks in during extended cloudy periods or unusually high hot water demand. Solar fraction is the key performance metric for solar thermal systems.
A system that uses rooftop collectors to heat domestic water using the sun's thermal energy — not to be confused with photovoltaic (electricity-generating) solar. Hawaii was the first state to require solar hot water on new residential construction (2010). Solar hot water has a shorter payback period than PV in many cases because water heating is a large, consistent energy load. We install both flat-plate and thermosyphon systems.
The total electromagnetic energy received from the sun, measured in kWh/m²/day. Hawaii receives 5.0-6.0 kWh/m²/day on average, with the leeward (west/south) sides of the islands receiving more than the windward (east) sides. Kona coast on the Big Island has some of the highest solar radiation in the state; windward Oahu (Kaneohe, Kailua) gets more cloud cover but still receives excellent solar resource by national standards.
A centralized inverter that handles the DC-to-AC conversion for an entire string (or multiple strings) of solar panels. String inverters are less expensive than microinverter systems but have a key disadvantage: if one panel in the string is shaded or underperforming, it drags down the entire string's output. They also have shorter warranties (typically 12-15 years) compared to microinverters' 25 years. SolarEdge string inverters with DC optimizers are a middle-ground option. For most Oahu residential roofs, we prefer Enphase microinverters.
A professional assessment of a roof's ability to support the additional weight of solar panels, racking, and associated equipment. Required by building code for certain roof types and older structures. In Hawaii, this is particularly important for post-and-pier homes, flat commercial roofs, and any structure where the original construction may not have been engineered for additional dead loads. A structural review typically costs $300-$800.
The rate at which a solar panel's power output decreases as temperature increases above 25°C (77°F). Measured in %/°C, a lower (less negative) coefficient is better. In Hawaii, where rooftop panels routinely reach 60-70°C, the temperature coefficient directly affects real-world production. HJT panels like the REC Alpha Pure-R have temperature coefficients around -0.26%/°C, compared to -0.34%/°C for standard PERC panels — that difference adds up to 3-4% more annual production in our climate.
The mobile application used to monitor and control Tesla Powerwall battery systems. The app shows real-time energy flow (solar production, home consumption, grid import/export, battery charge level), historical data, storm watch alerts, and allows you to adjust backup reserve percentages and operating modes. It's one of the better-designed energy monitoring apps on the market, and most of our Powerwall customers check it daily for the first few months.
A solar hot water system design where the storage tank sits above the collector, allowing natural convection (hot water rises) to circulate water without a pump. Thermosyphon systems are simpler and cheaper than active (pumped) systems, with fewer moving parts to fail. They're extremely common in Hawaii — you've seen the horizontal tanks sitting on rooftops across the islands. The trade-off is aesthetic (the tank is visible on the roof) and weight (the roof must support a full tank).
The angle at which a solar panel is tilted relative to horizontal, measured in degrees. For maximum annual production in Hawaii (latitude ~21°N), the optimal tilt is roughly 20-22 degrees. Most Oahu roofs have pitches between 15-25 degrees, which is close enough to optimal that flush-mounting on the existing roof slope makes economic sense. Ground mounts and flat-roof ballasted systems allow precise tilt adjustment.
A rate structure where the price of electricity varies by time of day. HECO's rates are effectively time-of-use through their export credit programs: energy exported during peak hours (evening) is worth more than energy exported midday. True TOU billing for consumption (paying more to draw power in the evening) is part of HECO's evolving rate design. TOU rates are the fundamental economic driver behind battery storage — buy low (or generate free solar), sell high (export at peak).
An advanced solar cell technology that achieves higher efficiency than standard PERC cells by adding a thin tunnel oxide layer and doped polysilicon to reduce electrical losses at the cell contacts. TOPCon panels are becoming increasingly common in the 2025-2026 market, offering efficiencies of 22-23%. They're a step up from PERC but use a different approach than HJT. Both TOPCon and HJT represent the current frontier of mainstream crystalline silicon technology.
An electrical device that switches a home's power source between the utility grid and a backup source (battery or generator). In solar-plus-battery systems, the transfer switch (built into devices like the Tesla Gateway) automatically disconnects from the grid during an outage and connects the battery, usually within milliseconds. This automatic transfer is what makes modern battery backup feel seamless — the lights don't even flicker.
The price per kilowatt-hour that HECO charges for electricity. As of early 2026, Oahu's residential rate is approximately $0.41/kWh — roughly triple the national average. The rate fluctuates monthly based on fuel costs, purchased power adjustments, and various surcharges. Hawaii's high utility rate is the single biggest reason solar pays for itself faster here than almost anywhere else. You can check current rates on your HECO bill or use our solar calculator to see what your specific rate means for solar savings.
Large solar farms (typically 1 MW and above) that sell electricity directly to the utility. Oahu has several utility-scale projects that contribute to HECO's renewable portfolio. Utility-scale solar is different from residential or commercial rooftop solar in scale, permitting, and economics, but it's part of the same statewide push toward Hawaii's 100% renewable energy goal by 2045.
The unit of electrical pressure that pushes current through a circuit. Your home runs on 120V (standard outlets) and 240V (dryer, oven, EV charger). Solar panels typically produce 30-50 volts each; when wired in series for a string inverter, the combined string voltage can exceed 400V. The NEC sets strict voltage limits for residential solar systems, and all wiring, conduit, and components must be rated for the system voltage.
The basic unit of electrical power. One watt is one joule of energy per second. Solar panels are rated in watts (or kilowatts) — a modern residential panel produces 400-450 watts under Standard Test Conditions. To put it in context: an LED light bulb uses about 10 watts, a mini-split AC unit uses 500-1,200 watts, and an electric vehicle charger draws 7,200-9,600 watts.
The rated power output of a solar panel under Standard Test Conditions (STC): 1,000 W/m² irradiance, 25°C cell temperature, and AM 1.5 spectrum. A "460 Wp" panel produces 460 watts under these lab conditions. Real-world production is always lower due to temperature, angle, soiling, and wiring losses — which is why the derate factor exists. Watt-peak is the common currency for comparing panels across manufacturers.
The methods and materials used to waterproof roof penetrations where solar mounting hardware is attached. In Hawaii, with annual rainfall exceeding 20 inches even in the driest areas (and over 150 inches in Manoa), weather sealing is critical. We use flashing, butyl tape, and sealant on every penetration point. A leak that goes undetected under solar panels can cause thousands of dollars in structural damage before anyone notices.
This glossary covers the most common terms, but solar and energy technology moves fast. If you've run into a term that's not listed here, or you want to understand how any of these concepts apply to your specific home, get in touch. No jargon, no pressure — just clear answers from people who do this every day.