Everything you need to know about home battery storage — what it costs, how it works, which batteries we install, and whether it’s the right investment for your home.
$0.329 per kilowatt-hour. That is what HECO pays for solar energy exported between 5pm and 9pm under the SRE Export program. During midday, that same energy is worth about $0.135. The 2.4x premium during peak hours is the single biggest reason battery storage went from “nice to have” to “obviously worth it” for Hawaii solar homeowners.
But peak rate arbitrage is only part of the story. Hawaii’s grid sits on isolated islands with no interconnection to the mainland. When a transmission line goes down or a power plant trips offline, there is no borrowing electricity from a neighboring state. Oahu experienced over a dozen significant outage events in 2025 alone, several lasting more than eight hours. If you live in Windward Oahu or on the North Shore, you already know what it feels like to lose power during a winter storm — and to wonder how long the food in your refrigerator will last.
The old net energy metering agreements that made battery-less solar a no-brainer are gone. NEM closed to new applicants years ago, and the customers still on it are watching their contracts tick toward expiration. Today’s solar programs — SRE Export and BYOD+ — are built around time-of-use economics. They reward you for storing solar energy and dispatching it when the grid needs it most. A solar system without a battery is still worthwhile in Hawaii (the rates are that extreme), but pairing solar with storage unlocks a fundamentally different value proposition: higher export credits, backup power during outages, and access to HECO incentive programs that are only available to battery owners.
There is also the practical reality of island living. Hurricane season runs June through November. Vog from Kilauea can reduce solar production for days at a stretch on the Big Island. Aging infrastructure means HECO sometimes curtails solar exports when the grid is saturated at midday. A battery absorbs all of that uncertainty and turns it into something useful: stored energy you control.
A home battery is a large lithium-iron-phosphate (LFP) unit that mounts on your garage wall, the side of your house, or on a concrete pad outside. It connects to your solar system and your electrical panel. That is it. No moving parts, no noise, no emissions, no maintenance beyond an occasional glance at the app.
During the day, your solar panels produce electricity. Your home uses what it needs first — running the AC, the refrigerator, the ceiling fans. Any excess production flows into the battery instead of going straight to the grid. The battery charges up over the course of the morning and early afternoon, typically reaching full capacity by 1pm or 2pm on a sunny day.
Then the peak window arrives. Between 5pm and 9pm, when HECO’s rates are highest and the grid is most strained, your battery discharges. It powers your home through the evening so you are not buying expensive grid electricity, and if your battery has more stored energy than you need, it exports the surplus to HECO at peak export credit rates. You are essentially time-shifting your solar production from the middle of the day, when it is least valuable, to the evening, when it is most valuable.
When the grid goes down, the battery does something else entirely. It disconnects your home from the utility grid within milliseconds (fast enough that most electronics never notice) and forms its own self-contained power system. Your solar panels continue producing, the battery continues storing, and your home operates independently until grid power returns. We have customers in Hawaii Kai who ran their entire house — AC included — for three days during a 2025 outage. They did not change their routine at all.
The intelligence behind this is software, not hardware. Both the Tesla and Enphase platforms use algorithms that learn your consumption patterns, track weather forecasts, monitor HECO rate schedules, and adjust charge/discharge behavior automatically. Tesla’s Storm Watch feature, for instance, detects incoming severe weather and fully charges the battery in advance, overriding any export optimization to make sure you have maximum backup capacity before the storm hits.
We install two battery platforms: Tesla Powerwall 3 and Enphase IQ Battery. After hundreds of installations with both, we have a clear sense of when each one is the right fit. They are not interchangeable products — they represent fundamentally different design philosophies, and the best choice depends on your home, your solar configuration, and what you need the battery to do.
The Powerwall 3 is Tesla’s all-in-one energy system. It has a built-in hybrid inverter, meaning it handles both solar conversion and battery storage in a single unit. One Powerwall delivers 13.5 kWh of usable storage and 11.5 kW of continuous power output — enough to run a typical three-bedroom Hawaii home with central air conditioning. The unit mounts on a wall or floor, indoors or outdoors, and communicates through the Tesla app.
For homes that need more capacity, Tesla offers the Powerwall 3 Expansion Pack — a 13.5 kWh battery-only unit that piggybacks off the main Powerwall’s inverter. You can stack up to three Expansion Packs per Powerwall, and up to four Powerwalls per home, which means storage configurations from 13.5 kWh all the way to 216 kWh. Most Hawaii homes land somewhere between 13.5 and 40.5 kWh.
What we like about the Powerwall in the field: the power output is exceptional. At 11.5 kW continuous, a single unit can handle heavy loads that would overwhelm smaller batteries. During a grid outage, the Powerwall can start a central AC compressor without flinching — something that matters when you are riding out a summer power failure in Ewa Beach and it is 88 degrees at 2pm.
Enphase takes the modular route. The IQ Battery 5P holds 5 kWh and outputs 3.84 kW continuous. The larger IQ Battery 10C holds 10.08 kWh at 7.68 kW. Both are AC-coupled, meaning they work alongside your existing microinverters rather than replacing them. You stack units to hit your target capacity.
The modularity is genuinely useful. We have installed Enphase batteries in Makiki condos and Manoa cottages where there simply was not enough wall space for a Powerwall. Three IQ Battery 5P units (15 kWh total) can be arranged in an L-shape, stacked vertically, or split across two walls. Try doing that with a Powerwall.
Enphase also has an advantage for existing solar systems with Enphase microinverters. Because the IQ Battery is AC-coupled, it integrates seamlessly with any existing Enphase system — no rewiring the solar array, no replacing the inverter. For battery retrofit projects, this often means a simpler installation and lower labor costs.
For a deeper dive into performance, backup behavior, and installer recommendations, see our full Powerwall vs Enphase Battery comparison. Here are the core specs side by side.
| Specification | Tesla Powerwall 3 | PW3 Expansion Pack | Enphase IQ 5P | Enphase IQ 10C |
|---|---|---|---|---|
| Usable Capacity | 13.5 kWh | 13.5 kWh | 5.0 kWh | 10.08 kWh |
| Continuous Power | 11.5 kW | — (uses PW3 inverter) | 3.84 kW | 7.68 kW |
| Peak Power | Up to 22 kW | — | 5.7 kW | 11.4 kW |
| Solar Inverter Built-in | Yes (hybrid) | No | No (AC-coupled) | No (AC-coupled) |
| Chemistry | LFP | LFP | LFP | LFP |
| Warranty | 10 years | 10 years | 15 years | 15 years |
| Dimensions | 43.3″ × 25.6″ × 8.2″ | 43.3″ × 25.6″ × 8.2″ | 26″ × 16″ × 7.3″ | 42.1″ × 16″ × 7.3″ |
| Weight | 287 lbs | 245 lbs | 99 lbs | 202 lbs |
| BYOD+ Compatible | Yes | Yes (with PW3) | Yes | Yes |
This is the question we get asked more than any other, and the honest answer is: it depends on two things. How much electricity your household uses per day, and what you want the battery to do.
If your primary goal is peak-rate optimization and BYOD+ participation — storing solar during the day and dispatching it during the 5–9pm peak window — then you need enough storage to cover your evening consumption plus whatever you want to export. For most Oahu homes, that is 10–15 kWh, which means a single Powerwall 3 or two to three Enphase IQ Battery 5P units handles it comfortably.
If your goal includes whole-home backup during extended outages, the math changes. You need to think about total daily consumption, not just the peak window. A family of four in Mililani running central AC, a refrigerator, and normal evening loads might draw 30–40 kWh over a 24-hour period. A single 13.5 kWh Powerwall will not cover that alone — but it does not have to, because your solar panels recharge the battery every day. In practice, one Powerwall plus a well-sized solar array can sustain most homes indefinitely through an outage, as long as you manage the heavy loads (skip the dryer, keep the AC at 76 instead of 72).
For homes that want full-comfort backup without any load management — run the AC freely, use the dryer, do not think about it — we typically recommend either a Powerwall 3 with one Expansion Pack (27 kWh total) or two standalone Powerwalls (27 kWh with 23 kW of continuous power). The extra power capacity means the system can start multiple large appliances simultaneously without tripping.
| Configuration | Total Storage | Continuous Power | Best For |
|---|---|---|---|
| 1 Powerwall 3 | 13.5 kWh | 11.5 kW | Peak optimization + essential backup for average homes (600–900 kWh/mo) |
| 1 PW3 + 1 Expansion | 27.0 kWh | 11.5 kW | Full-comfort backup for medium homes; high-usage peak optimization |
| 2 Powerwall 3s | 27.0 kWh | 23.0 kW | Large homes with central AC, EV charging, ohana unit; maximum power headroom |
| 2 PW3 + 1 Expansion | 40.5 kWh | 23.0 kW | Multi-day backup for large homes; heavy BYOD+ export |
| 2 × Enphase IQ 5P | 10.0 kWh | 7.68 kW | Efficient homes, peak optimization, partial backup |
| 3 × Enphase IQ 5P | 15.0 kWh | 11.52 kW | Comparable to 1 Powerwall; great for Enphase microinverter homes |
| 1 × Enphase IQ 10C | 10.08 kWh | 7.68 kW | Compact single-unit solution; moderate usage homes |
We size every battery system based on 12 months of actual HECO usage data, your solar production profile, and what you tell us about your backup priorities. The solar calculator on our site gives you a starting estimate, but the detailed sizing happens during our site evaluation when we review your electrical panel, consumption history, and critical load requirements.
A home battery system in Hawaii is not cheap. A single Tesla Powerwall 3 installed typically runs $14,000–$16,000. A Powerwall 3 with one Expansion Pack lands around $24,000–$28,000. Enphase systems fall in a similar range depending on configuration. These are real numbers, and we are not going to pretend otherwise. For a deeper breakdown of Powerwall pricing, see our Tesla Powerwall cost guide for 2026.
But the economics of battery storage in Hawaii are unlike anywhere else in the country, and three financial levers work in your favor simultaneously.
The federal Residential Clean Energy Credit covers 30% of the cost of a battery storage system, including installation labor. This applies to standalone battery installations, not just batteries paired with new solar. A $16,000 Powerwall installation generates a $4,800 tax credit. A $27,000 system with an Expansion Pack yields $8,100 back. The credit is a dollar-for-dollar reduction in your federal tax liability — not a deduction, not a rebate, but actual money off your tax bill. It is available through 2032, steps down to 26% in 2033, and expires in 2034.
One important nuance: you need enough federal tax liability to claim the credit. If your household owes $6,000 in federal taxes and your credit is $8,100, you take $6,000 this year and roll the remaining $2,100 forward to next year. Most Hawaii households with two working adults clear this threshold without issue. For details on combining it with state incentives, see our financing guide.
HECO’s Bring Your Own Device Plus (BYOD+) program pays you to let HECO dispatch your battery during grid stress events. The upfront incentive is $850 per kW of dispatch capacity. A standard Powerwall 3 with 5 kW of dispatchable capacity earns $4,250 upfront. We cover BYOD+ in detail in its own section below, but the financial headline is clear: BYOD+ can offset 25–30% of your battery cost on top of the federal credit.
This is where the ongoing savings live. HECO’s time-of-use rate structure means you pay roughly $0.41–$0.52 per kWh during the 5–9pm peak window (depending on your rate schedule) and significantly less during midday. A battery charged with free solar electricity during the day and discharged during peak hours saves you the full peak rate for every kWh you self-consume. If your household uses 15 kWh between 5pm and 9pm — a typical evening for a family with AC — that is $6–$8 per day in avoided peak-rate purchases, or roughly $180–$240 per month.
For homes on the SRE Export program, there is an export angle too. Solar exported during midday earns about $0.135/kWh. The same energy stored in a battery and exported during the peak window earns $0.329/kWh. The battery effectively doubles the value of every kWh you send to the grid during peak hours.
The payback math on a battery system in Hawaii looks like this. Take a $16,000 Powerwall 3 installation. Subtract the 30% federal credit ($4,800) and the BYOD+ upfront incentive ($4,250). Your net out-of-pocket cost is approximately $6,950. If peak rate arbitrage and BYOD+ monthly credits save you $200 per month (a conservative estimate for a household using 800+ kWh/month), payback lands around three years. That is aggressive compared to the national average, but Hawaii’s electricity rates are aggressive too.
Even the most conservative analysis — assuming no rate increases and minimal BYOD+ credits — puts battery payback in Hawaii between four and seven years. The battery is warrantied for 10 years and has an expected lifespan of 15+. Everything after payback is savings.
BYOD+ is HECO’s flagship demand response program for residential battery owners, and it is one of the most generous utility battery incentive programs in the country. The concept is straightforward: you install a battery, enroll in BYOD+, and HECO gains the ability to dispatch a portion of your battery’s capacity during grid stress events. In return, you get paid — both upfront and on an ongoing monthly basis.
For a full breakdown of all active HECO programs including SRE Export, see our HECO programs guide.
When HECO calls a dispatch event — typically during the 5–9pm peak window on hot days when grid demand spikes — your battery automatically exports energy to the grid. You do not do anything; the battery and HECO’s aggregation platform handle the communication. Dispatch events usually last 1–2 hours. HECO can call events up to a set number of times per month, and your battery retains enough reserve to keep your home powered during and after dispatch.
In practice, dispatch events often align with when you would be exporting stored solar energy at peak rates anyway. The battery is already planning to discharge during the evening; BYOD+ simply compensates you additionally for that discharge being available to stabilize the grid.
The upfront capacity payment is $850 per kW of dispatchable capacity. A Powerwall 3 with 5 kW enrolled earns $4,250 upfront. Two Powerwalls at 10 kW total earn $8,500. Monthly performance credits add another layer of ongoing compensation, though the exact amount varies based on dispatch frequency and your system’s response performance.
There is also an LMI (low-to-moderate income) adder for qualifying households. If your household income falls below 80% of the area median income, you receive a higher per-kW incentive — HECO’s way of making battery storage accessible beyond the typical early-adopter demographic.
BYOD+ enrollment is a 5-year commitment. During that period, your battery must remain installed, operational, and available for dispatch. If you remove the battery or withdraw from the program before the term ends, you may have to return a prorated portion of the upfront incentive. This is reasonable — HECO is paying you upfront because they are counting on your battery being available for five years of grid support. In our experience, no customer has ever wanted to withdraw. The battery is doing what they bought it for, and the BYOD+ payments are found money on top of the daily savings they are already earning.
About 40% of our battery installations are retrofits — adding storage to a home that already has a solar array. The process is different from a new solar+battery installation, and the differences affect cost, timeline, and equipment choices. We wrote an entire guide on this topic: adding battery to existing solar in Hawaii.
When you add a battery to an existing solar system, the biggest variable is your current inverter. If you have Enphase microinverters (IQ7 or IQ8 series), an Enphase IQ Battery is the simplest path. It is AC-coupled and plugs into your existing Enphase ecosystem without touching the solar array at all. The installation is typically a one-day job: mount the battery, wire it to the panel, configure the Enphase software, and done.
Adding a Tesla Powerwall 3 to an existing system is also straightforward, but the Powerwall’s built-in hybrid inverter creates an option that can simplify the overall system. For older systems with aging string inverters, the Powerwall can potentially replace the solar inverter entirely, consolidating two pieces of equipment into one. Our crew evaluates this on a case-by-case basis.
Retrofit costs typically run $1,000–$2,000 less than new-install costs because the electrical infrastructure (main panel, conduit runs, HECO meter) is already in place from the original solar installation. Permitting is also simpler since the structural and electrical review for the original system is already on file with the county.
When we install solar and battery together on a new project, everything is designed as an integrated system from the start. Panel count, inverter configuration, battery size, and export strategy are all optimized together. The Powerwall 3’s built-in hybrid inverter is particularly efficient here because it eliminates the need for a separate solar inverter entirely — the panels wire directly into the Powerwall.
New installations also qualify for the most favorable HECO program terms and the cleanest permitting path, since there are no legacy system complications. The total project cost for solar+battery is higher, of course, but the cost per component is often lower because of installation efficiencies. For full pricing details, see our solar installation service page.
Home batteries require almost no maintenance. Seriously. There are no filters to change, no fluids to check, no moving parts to wear out. The unit sits on your wall, silently cycling through charge and discharge cycles, managed entirely by software. We tell our customers to check the app once a week if they are curious, but most people forget the battery is even there until the power goes out and everything keeps running.
Both Tesla and Enphase use lithium-iron-phosphate (LFP) chemistry in their current products. LFP is inherently more stable and longer-lasting than the older NMC (nickel-manganese-cobalt) chemistry used in earlier battery generations. It tolerates heat better — relevant in a garage in Kapolei in August — and degrades more slowly over thousands of charge cycles.
Tesla warranties the Powerwall 3 for 10 years with a guaranteed 70% capacity retention at end of warranty. Enphase warranties the IQ Battery for 15 years at 70% retention. In practice, LFP batteries typically retain 80–85% of their original capacity at the 10-year mark and remain functional well beyond 15 years. The battery will not suddenly stop working at year 11; it will gradually hold slightly less energy per cycle, the same way a phone battery slowly loses capacity over years of use — except much, much more slowly.
The one maintenance consideration worth mentioning: keep the area around the battery clear of debris, and make sure the unit has adequate ventilation. Batteries generate a small amount of heat during cycling, and the built-in thermal management system needs airflow to function properly. If you are wall-mounting in a garage, leave at least six inches of clearance on all sides. Our installation team handles the placement and clearance requirements during install, but we mention it because we have seen exactly one case where a homeowner stacked storage bins against a Powerwall and caused a thermal throttling warning. Do not stack things against your battery.
Technically, yes. Practically, we almost never recommend it for Oahu homes. Going off-grid requires significantly oversizing both your solar array and battery bank to cover worst-case scenarios — multiple cloudy days, high AC usage, winter months with shorter daylight hours. The cost of a truly off-grid system is typically 2–3x the cost of a grid-tied solar+battery system, and you lose access to HECO export credits and BYOD+ incentives. For most homeowners, staying grid-tied with battery backup gives you 95% of the energy independence at a fraction of the cost. For more on this topic, see our grid-tied vs off-grid comparison.
A Powerwall 3 can start and run a central AC system without issue — the 11.5 kW continuous output handles the compressor startup surge that causes smaller batteries to trip. An Enphase setup needs enough stacked capacity (typically three IQ 5P units or more) to handle that same surge. The real question is how long you want the AC to run. A single Powerwall supporting a 3-ton AC system will drain in roughly 4–5 hours without solar recharging. With solar panels producing during the day, the system can sustain AC essentially indefinitely during daylight hours and provide 6–8 hours of evening runtime, depending on your thermostat setting and home insulation.
The battery transfers with the property, just like the solar panels. It is a permanent fixture. Our systems are owned, not leased, so there is no lease transfer headache — the new owner simply takes over the Tesla or Enphase account. If you are enrolled in BYOD+, the program agreement transfers to the new homeowner. Research consistently shows that homes with owned solar and battery systems sell for more, not less, so the battery is an asset, not a complication.
The Powerwall 3 is essentially silent during normal operation. During heavy cycling (charging or discharging at full power), the internal fans produce a faint hum comparable to a refrigerator — you can hear it if you stand next to the unit in a quiet garage, but not from inside the house. Enphase IQ Batteries are also very quiet. Neither product has been a noise issue for any of our customers, including those with batteries mounted on exterior walls adjacent to bedrooms.
Sometimes. If your home still has a 100-amp main panel (common in older Hawaii homes built before 1990), adding a battery system often requires a panel upgrade to 200 amps. This adds $2,000–$4,000 to the project cost and a couple of extra weeks to the timeline. Homes with existing 200-amp service typically do not need a panel upgrade. Our site evaluation catches this early so there are no surprises during installation. For more on electrical panel upgrades for solar, we have a separate guide.
Yes, and we do this regularly. The most common scenario is a customer who installed a single Powerwall with their solar system, lived with it for a year, and decided they wanted more backup capacity or wanted to maximize their BYOD+ enrollment. Adding a Powerwall Expansion Pack or additional Enphase units to an existing battery system is a straightforward retrofit. The permitting is simpler than the original installation, and the new capacity integrates with the existing system automatically. We recommend sizing for your current needs and expanding later rather than overbuying upfront — battery technology continues to improve, and the unit you add in two years may offer better specs at a lower price.
Every home is different. Start with our free solar calculator to estimate your system size and savings, or request a no-obligation site evaluation from our team. We’ll pull your HECO usage data, assess your electrical panel, and give you an honest recommendation — including whether battery storage even makes sense for your situation.