Home battery warranty throughput: how many years before the MWh cap ends coverage?

Two limits on one promise: calendar years and megawatt-hours

Every battery warranty in this comparison makes two promises at once. The first is a defect warranty: the unit will be free of defects in materials and workmanship for a stated period. The second is a capacity promise: at the end of the period the battery will still store some fixed share of its rated energy, usually 70 percent. The throughput cap attaches to the capacity promise. LG Energy Solution's Prime warranty puts it plainly, guaranteeing 70 percent energy retention at the earlier of the end of the 10-year period or the point where aggregate energy throughput reaches the figure in its table.

Throughput is a running total of energy through the battery, kept by the battery's own management system and read by the manufacturer over the internet connection the warranty requires. A rated 15 kWh battery that discharges 15 kWh has done one full cycle; two half-discharges of 7.5 kWh add up to the same thing. So a cap in MWh can always be turned into a count of full-cycle equivalents by dividing it by the rated kWh: 60 MWh on a 15 kWh battery is 4,000 full cycles, and 32 MWh on a 9.6 kWh battery is 3,333.

Enphase writes its cap the other way round, as cycles rather than energy. The IQ Battery 5P warranty period ends at the earlier of 15 years from activation or 6,000 discharged cycles. The document does not define a discharged cycle, so whether a shallow evening discharge counts as one cycle or as a fraction is something to ask Enphase in writing before you plan around the number. The FranklinWH and LG documents likewise do not say whether their throughput counts energy in, energy out, or both; LG says only that it measures the figure itself.

SolarEdge takes a third approach. Its North American Home Battery 400V warranty lists "unlimited cycles" for standard solar use, meaning solar self-consumption, time of use, backup and SolarEdge-managed services, and switches to a 26 MWh cap when the battery is under third-party management. The same battery can therefore sit under an uncapped warranty or a capped one, depending on who is telling it when to discharge.

Four US warranty documents, set side by side

The table lists what each manufacturer's US or North American warranty document says, by product, with the version or date printed on the document. It is a record of terms, not a ranking: a longer term or a bigger cap means nothing until it is divided by the battery's size and set against how the battery will be used, which the next two sections do.

Three things stand out once the rows sit together. The caps are not comparable as printed, because 60 MWh on a 15 kWh battery and 32 MWh on a 9.6 kWh battery describe different amounts of daily use. The capacity floor is 70 percent in every document except Enphase's second step, which drops to 60 percent for the last five years of its term. And two of the documents start the clock before the battery reaches your wall: a FranklinWH unit installed 14 months after it was built has already spent two months of its warranty in a warehouse.

Tesla is missing for a plain reason. Its US Powerwall 3 warranty is a PDF on tesla.com, it could not be retrieved on the check date, and the Internet Archive holds no copy of that file. Rather than fill the row from installer blogs or review sites, the row is left blank. If you are weighing a Powerwall, ask for the US warranty document by its version date and run its figures through the same division used below.

Turning each cap into a daily kilowatt-hour allowance

A cap and a term together define a daily energy allowance: the amount the battery can move every day, on average, and reach the cap exactly on the last day of the term. Below that allowance the calendar ends your coverage; above it, the cap does. The allowance is simply the cap divided by the days in the term, and dividing it by the battery's size turns it into cycles a day.

The crossover sits between about 0.7 and 1.1 cycles a day for every capped product. That is the zone a battery used for daily solar shifting tends to live in, which is why the cap is not a footnote. A household that only keeps the battery charged for outages and lets it sit full most days will almost never meet a cap, while a household on a time-of-use rate that empties the battery every evening is running close to or above one cycle a day for much of the year.

Two cautions apply to the allowance column. It is an average, so a winter of light use followed by a summer of heavy use can land in the same place as steady use. And it counts energy the battery moves, not energy your home receives: with round-trip losses, the energy charged in is larger than the energy delivered, and the warranty text decides which side counts. Enphase's cap is in discharged cycles, but the three MWh documents do not say which side they meter. The battery cost guide works through those round-trip losses in dollars per delivered kWh.

Years of coverage at half, one and one-and-a-half cycles a day

Years to the cap are the cap divided by the energy moved in a year: MWh times 1,000, divided by rated kWh times cycles a day times 365. For the LG RESU 10H Prime at one cycle a day that is 32,000 divided by 3,504, or 9.13 years, so a once-a-day owner loses about ten months of capacity coverage against the 10-year term. Every row below was worked the same way and checked by hand once; the shorter of the two limits is the one that governs.

At one cycle a day the products sort into two groups: those whose crossover sits below one cycle (FranklinWH, LG and SolarEdge under third-party control), where the cap arrives first, and Enphase, where 6,000 cycles outlast a 15-year term until use rises past about 1.1 cycles a day. At one and a half cycles a day, a pattern that takes a utility program or two daily price peaks to reach, every capped product runs out of throughput years before its term.

Full cycles are an upper bound on use, and real batteries rarely do them. Most installations hold back a reserve for outages, often a fifth or more of the capacity, so a nominal daily cycle moves less energy than the rated kWh and the cap lasts longer than the table says. Set your installer's monitoring data, or the first few months of your own, against the daily allowance column above rather than assuming a full cycle. The time-of-use guide shows how much evening shifting a typical rate schedule actually rewards, which is the usual reason a battery cycles daily in the first place.

Utility dispatch: the cycles you do not schedule yourself

A virtual power plant program pays you to let the utility or an aggregator discharge your battery during peak events. Each event is energy through the battery, and it counts toward the cap the same way your own evening use does. The virtual power plant guide reads seven programs' terms and payments; this section looks only at what the extra discharges do to warranty years.

Take a household that shifts solar into the evening at 0.7 full cycles a day on average, and add 60 full discharges a year for utility events. The 60 is an illustration chosen to show the effect, not a figure from any program's terms. On a FranklinWH aPower 2, 0.7 cycles a day moves 3,832.5 kWh a year and reaches 60 MWh in 15.7 years, so the 15-year term governs. Add the 60 events, another 900 kWh, and the cap arrives in 12.7 years: the program has taken more than two years off the capacity coverage. The aPower X goes the same way, from 12.4 years to the cap (past its 12-year term) to 10.0 years. The LG Prime batteries still reach their 10-year term first, at about 10.6 and 10.7 years to the cap, but with almost no margin. An Enphase IQ Battery 5P moves from 23.5 years to 19.0 years to its 6,000 cycles, still past its 15-year term.

The terms matter more than the arithmetic for two of the documents. SolarEdge's unlimited cycles apply to SolarEdge-managed services; under third-party management the warranty is limited to 26 MWh. For a 9.7 kWh battery doing the same 0.7 cycles a day plus 60 events, that cap arrives in 8.5 years, before the 10-year term. Whether a given utility program counts as third-party management is a question for SolarEdge, answered in writing, before you enroll. LG's performance warranty is written for one stated application, residential storage for solar self-consumption or backup, and its general exclusions remove coverage when the products are used for purposes other than that application. The document says nothing specific about grid services, so the same written confirmation applies before an LG Prime goes into a dispatch program.

None of this makes a program a bad deal. A payment that recovers part of the battery's price can be worth more than the last few years of capacity coverage, particularly on a battery whose cap was never going to be reached. It does mean the program's payment should be set against the warranted years it uses, which is the comparison the program terms alone do not show.

One garage battery, three dates that decide its coverage

A household in a cold-winter state installs a FranklinWH aPower 2 in a detached garage in June 2026. The unit's label shows a manufacture date of March 2025. It cycles about 0.7 times a day on a time-of-use rate, and the owners are considering a utility program that would add about 60 full discharges a year. All figures here are illustrations built from the warranty's own terms.

Start date first. Twelve months from manufacture is March 2026, earlier than the June installation, so the 15-year term runs to March 2041, not June 2041: three months gone. Throughput next. At 0.7 cycles alone, 3,832.5 kWh a year reaches 60 MWh in about 15.7 years, past the term, so the calendar governs. With the program, 4,732.5 kWh a year reaches the cap in about 12.7 years, around late 2038 counting from the March 2026 start, more than two years before the term ends.

Then the conditions. The garage location has to stay inside FranklinWH's temperature guidance, and the program's aggregator will need the battery online, which also protects the 15-year term from the 90-day disconnection clause. The household's decision comes down to whether the program's payments over twelve-plus years outweigh losing the capacity promise for the last two-plus years, which is a smaller question than whether to enroll at all.

Conditions in the documents that cut coverage short

A throughput cap is the visible limit. The conditions buried in each document can end coverage much earlier, and several of them depend on things an owner does years after installation, such as changing the home's internet service or moving the battery during a remodel.

The internet rows are the ones most owners break by accident. A router replaced during a move, a changed Wi-Fi password, or a cancelled cellular plan on a monitoring gateway can leave a battery offline for months without any visible symptom, because the battery keeps working. Under the FranklinWH document, 90 consecutive days offline followed by an unanswered reconnection notice turns a 15-year warranty into a 4-year one, which for a battery already past its fourth year means no warranty at all. Under SolarEdge's, a battery that is not connected to the monitoring platform is not covered. Checking the monitoring app once a month is cheap insurance against that clause.

The temperature rows overlap with placement. SolarEdge's limit on days below freezing, no more than 30 percent of any rolling year, is a real constraint for a battery mounted on an unheated garage wall in a cold state, and the battery installation location guide covers where code lets a battery go before the warranty narrows it further. LG's grid-connection requirement rules out its Prime batteries for an off-grid cabin under this document; the off-grid solar cost guide covers that design separately.

Every document also excludes the familiar list: misuse, unauthorized repair, fire, flood, lightning and power surges, and cosmetic damage that does not affect function. Surge and lightning exclusions are the ones to read twice, because they are plausible causes of a real failure and none of the four documents carves out an exception for them. That loss falls to the homeowners policy, if anywhere.

Warranty points to pin down at the quote stage

• The warranty document itself, with its version or effective date, for the exact model and SKU being installed, not a brochure summary.
• The battery's rated or usable kWh as the warranty uses it, so the cap can be divided into full-cycle equivalents.
• Whether throughput counts energy charged, energy discharged, or both, and for Enphase, how a partial discharge is counted.
• The manufacture or shipment date on the unit, since the clock may already be running.
• Written confirmation of how any utility or aggregator program you might join is treated: standard use, third-party management, or outside the covered application.
• Who pays labor to remove and reinstall a replacement, and which certified installer will do it if the original one is gone.
• How the battery stays online: the network it uses, who owns that account, and what happens when you change internet providers.
• The transfer steps and any fee, if you might sell the house within the term.

When the warranty clock starts before installation

Two of the four documents start the warranty at installation or at a fixed time after the battery was built, whichever comes first: FranklinWH uses 12 months from manufacture and LG uses 36. SolarEdge names both the installation date and 12 months from shipment without saying which applies when they differ, which is worth settling with the installer. Enphase alone starts at activation, defined as the earlier of registration or activation after the system has permission to operate.

The difference matters in a supply chain where batteries sit in distributor stock. A FranklinWH aPower 2 built in January 2025 and installed in May 2026 started its 15-year term in January 2026, twelve months after manufacture, and has lost four months of coverage before it holds a single charge. The throughput cap is unaffected, since the battery has moved no energy, but the calendar term now ends four months earlier. A manufacture date is printed on the unit's label; asking for it before installation, and for a newer unit if it is old, costs nothing.

For a battery added to an existing solar system, the start rule interacts with the inverter's own warranty, which may be years into its term already. A new battery on an old inverter can outlast the inverter's coverage, and an LG Prime battery is only covered with an approved, compatible inverter, so a future inverter replacement has to stay on the compatibility list. The inverter replacement guide sets out what that replacement typically involves.

What a successful capacity claim actually pays

Suppose the battery fails its capacity promise inside the term and under the cap. Every document reserves the remedy for the manufacturer. Enphase will repair or replace, and refunds only when replacement is impossible and repair impractical or when you accept a refund; the refund is the purchase price less reasonable depreciation based on use. FranklinWH has the same structure. SolarEdge may repair, replace with an equivalent product, or issue a credit note worth up to the value of the lost capacity, usable only toward SolarEdge products.

Replacement does not restart anything. Under the FranklinWH and LG documents, a repaired or replacement unit carries only the remainder of the original period, and FranklinWH says the original period is never extended. Enphase gives the remainder of the original period or 90 days from receipt, whichever is later, and may use reconditioned parts; LG replaces with refurbished parts equal in value. A replacement battery in year eight of a ten-year term has two years of coverage, not ten.

Labor is the other gap. Enphase's warranty says in its exclusions that it does not include the cost of labor to uninstall the covered product or reinstall a repaired or replacement one, and SolarEdge's says that labor, travel and on-site costs of uninstalling and reinstalling are borne by the buyer unless SolarEdge agrees otherwise in writing in advance. A replacement unit shipped free can still arrive with an installer invoice attached, and if the original installer has closed, certified replacements may be harder to schedule under the FranklinWH and LG documents, which require certified personnel for service.

A prorated refund on someone else's invoice

LG's performance warranty pays out on a schedule when a replacement product is no longer commercially available: residual value equals the purchase price divided by 120, times 120 minus the months since installation, with nothing from the 121st month. A battery that fails its capacity promise in month 84 is therefore worth 36/120 of its price, or 30 percent. The catch is the price itself. The document defines the purchase price as the price paid by the reseller or certified installer, not the price on the homeowner's contract, which includes installation, margin and permits. The refund is a share of a wholesale figure you never saw, so ask for it in writing at purchase if the remedy matters to you.

Pricing a warranted kilowatt-hour

Throughput gives a way to put a price on what the warranty actually covers. The DOE Solar Photovoltaic System Cost Benchmarks for the first quarter of 2025 model an 8 kW residential system with 13.5 kWh of storage at $4.59 per watt DC, against $2.95 per watt DC for the same system without storage, both in 2024 dollars. At 8,000 watts that is $36,720 against $23,600, so the modeled storage increment is $13,120. It is a national comparison line, not a quote.

Divide that increment by the energy a warranty would cover on a 13.5 kWh battery and you have a cost per warranted kWh. At 3,000 full-cycle equivalents, a round figure a little below the LG and FranklinWH aPower X ratios, the battery is warranted for 40.5 MWh and each warranted kWh costs about 32 cents. At 4,000, the aPower 2's ratio, it is 54 MWh and about 24 cents. At 6,000, the Enphase cycle count, it is 81 MWh and about 16 cents. These are illustrations of a 13.5 kWh battery at the benchmark price, not prices for any product in the table, and they assume the battery uses its full allowance within the term, which the half-cycle-a-day owner never does.

That last point is the useful one. An owner who will cycle half a day hits the calendar long before the cap, so the cap is worth nothing extra to them and the cost per kWh they actually use is much higher than the warranted figure. The lifetime cost of each delivered kWh is the right comparison against an evening electricity price, and the battery decision guide sets that against backup value, which a warranty in MWh cannot price at all.

Selling the house with the battery on the wall

A battery warranty that does not transfer is worth nothing to a buyer, and the documents differ in what a transfer takes. Enphase extends coverage to a later owner only if the product stays at its original location, the new owner submits a change-of-ownership form and pays a transfer fee within 30 days of the transfer, and registers; the fee amount sits on the form and can change at Enphase's discretion. SolarEdge's warranty transfers to any assignee for the remaining period, provided the battery has not been moved or reinstalled. FranklinWH's claim instructions ask a later owner for documentation of the ownership change along with the original proof of purchase.

A buyer also inherits whatever throughput the battery has already used. A five-year-old aPower 2 that has averaged one cycle a day has used about 27.4 MWh of its 60, so roughly 6 years of cap remain at the same pace against 10 years of term. The battery's monitoring account holds the running total; ask the seller to export it, along with the warranty document version and the installation date. How a battery affects the sale price and the payoff of an unpaid loan is covered in payback if you move or sell.