Equipment

Off-grid vs grid-tied solar

Your panels work in a power cut. Your inverter is listed not to.

Updated September 2026 · Data as of Building code text read on 3 September 2026

Written by HyreSolar Research team Research and analysis

Audited by HyreSolar Research team Data audit and fact check

Listed to disconnect, not broken Why grid-tied goes dark

NFPA 70 is where the building code sends the design And it is paywalled

Separate article for stand-alone systems A different regulatory object

The short answer

One sentence in the building code separates these systems, and once you have read it the most confusing thing about solar stops being confusing. The equipment listing provision says: "Systems connected to the utility grid shall use inverters listed for utility interaction." A utility-interactive listing is what carries the behaviour that disconnects the inverter when the grid goes down. So a plain grid-tied system produces nothing during a power cut, and that is not a fault or an oversight. It is a listing requirement. The inverter is certified to stop, because a system feeding a dead line endangers the people repairing it. Off-grid is a different regulatory object entirely, with its own dedicated provisions in the electrical code, and the code is explicit that the electrical design of any solar system is handed over to that standard rather than governed by the building code. That standard is copyrighted and paywalled, which is why so much of what governs your system is something you are not able to read.

The sentence that explains the whole thing

The most common complaint about residential solar is a version of the same discovery: the power went out, the sun was shining, and the system did nothing. People assume something failed. Nothing failed.

The equipment listing provision of the residential code says, in full: "Photovoltaic panels and modules shall be listed and labeled in accordance with UL 1703 or with both UL 61730-1 and UL 61730-2. Inverters shall be listed and labeled in accordance with UL 1741. Systems connected to the utility grid shall use inverters listed for utility interaction." The same sentence appears in the building code for other buildings.

That third sentence is the dividing line. Not a performance difference, not a design philosophy, not a product tier. A listing category. An inverter listed for utility interaction has been evaluated for the behaviour that matters when it is connected to a live network, including ceasing to energise a line that has gone dead.

The reason is a safety one and it is not about you. A line worker approaching a fault has isolated the network and expects it to be dead. A house exporting into that line makes it live. The behaviour that prevents this is designed in, tested, and certified, and it is why your inverter shuts down at the moment you most want it running.

So the question "why doesn't my solar work in a power cut" has a precise answer: because the code requires a grid-connected system to use an inverter listed to stop. If you want production during an outage, you are not fixing a problem. You are buying a different kind of system.

What the listing clause actually requires, component by component

Component	Required listing	Why it is in the clause
Panels and modules	Listed and labelled to UL 1703, or to both UL 61730-1 and UL 61730-2	The older standard or the newer two-part international pair. Either satisfies the requirement, which is why you see both cited on data sheets
Inverters	Listed and labelled to UL 1741	The baseline listing every inverter needs, grid-connected or not
Inverters, if grid-connected	Additionally listed for utility interaction	This is the whole distinction. An inverter without it may not be connected to the grid
Mounting systems	Listed and labelled to UL 2703, installed per the manufacturer's instructions and their listings	The racking is a listed component too, and installing it outside its listing breaks compliance even if it holds
Building-integrated products	Roof coverings and roof assemblies listed and labelled to UL 7103	Solar shingles and integrated roof products are a separate listed category from panels on racks

From the equipment listing provisions of the 2024 residential and building codes, read 3 September 2026.

Notice that the inverter appears twice. Every inverter needs the baseline listing. A grid-connected one needs an additional listing on top. That two-step structure is the cleanest way to understand what the categories actually are, and it is not how the market describes them.

The three systems, described by what they are rather than by what they cost

Marketing describes these as tiers, from basic to premium. That framing is wrong, because they solve different problems and the most expensive is not the best for most people.

Grid-tied. Panels, an inverter listed for utility interaction, and a connection to the network. It offsets your consumption while the sun shines and exports the surplus. It has no storage and no ability to run independently, and during an outage it produces nothing. It is the simplest system, the cheapest, and the one with the fewest components to fail.

Grid-tied with storage, usually called hybrid. The same connection to the network, plus a battery and the equipment needed to run a defined part of the house independently when the grid is down. It is a grid-connected system that can deliberately island itself in a controlled way, which is a different thing from a system that is not connected at all.

Off-grid, or in the code's language stand-alone. No utility connection. Everything the house uses comes from generation and storage on site, plus whatever fuel-burning backup the owner has provided. It is not a bigger version of the other two; it is a different design problem, because there is nothing to fall back on.

The code treats the third one as its own subject. The electrical code contains a dedicated provision for stand-alone systems within its solar photovoltaic article, and a separate article for stand-alone systems among its special conditions. Parallel provisions for fuel cells and for wind carry stand-alone identification requirements too. The existence of that structure is the point: a system with no utility behind it is regulated as a distinct object, not as a grid-tied system with the wire removed.

We are not going to tell you what those provisions require, because we could not read them. Their existence is confirmed. Their text is behind a paywall, and we will come back to why that matters.

The rules that govern your system are ones you are not able to read

The residential code delegates the electrical design out of itself entirely. Its own words: "The electrical portion of solar PV systems shall be designed and installed in accordance with NFPA 70." Everything about conductors, disconnects, overcurrent protection, rapid shutdown, grounding and stand-alone systems is governed by that standard, not by the building code you can read for free.

That standard is copyrighted and sold. We attempted its text repeatedly across this research and could not obtain it. The provisions on optional standby systems, stand-alone systems, electric vehicle power transfer, rapid shutdown and stand-alone photovoltaic systems are all behind the same wall.

The practical consequence for a homeowner is real. When an installer tells you the code requires something, you cannot check. When a jurisdiction refuses a design, you cannot read the clause. The parts of the rules we can quote on this site are the building-code parts, because those are published openly, and the parts we cannot quote are the electrical ones, which is most of what determines how your system works.

What to do about it. The publisher offers a free read-only access route behind registration, which we did not use for this page. If you need to verify a specific clause, that route exists, and your local building department holds the adopted edition. Do not accept "the code says" as an answer without a clause number you can go and look at.

What has to be added to make a system run during an outage

Backup capability is where we have to be honest about the limits of what we could source, because it is the question most people arrive with.

The code hook is clear. A grid-connected system uses an inverter listed for utility interaction, which is listed to cease energising when the grid goes down. To run during an outage, the system must be able to separate itself from the network in a controlled way and then operate as its own small island, safely and without back-feeding.

What we could not find is any primary source stating the hardware list. No code provision we could read, and no federal document, sets out what a grid-tied system needs added to it. That is manufacturer territory rather than code territory, and the manufacturers describe their own products rather than the general requirement.

What manufacturer documentation does establish, and we cover it in detail separately, is that the equipment has consolidated. One system's controller is described as containing an inbuilt neutral forming transformer, microgrid interconnection device, automatic transfer switch, and panel board in a single enclosure. The functions that used to be separate boxes are now inside one product, which is why asking "do I need a transfer switch" often gets a confusing answer: you do, and it is already in there.

The other thing that consolidation hides is that the decision about which circuits run is made at quote time and then physically wired. That is the subject that most deserves your attention if outage performance is what you are buying, and we treat it as its own page.

And the battery requirements apply whichever system you choose. Residential storage must be listed and labelled to UL 9540, with restrictions on where units may be placed, a minimum separation between units, clearances from doors and windows, and construction requirements for the walls and ceilings of the space. Those provisions are in the residential code and we quote them in full elsewhere. They apply to a hybrid system and to an off-grid one alike.

The three systems compared on what actually differs

Question	Grid-tied	Hybrid	Off-grid
Inverter listing required	UL 1741 and listed for utility interaction	UL 1741 and listed for utility interaction, because it is still grid-connected	UL 1741. Not for utility interaction, because there is no utility to interact with
Produces during an outage	No. The inverter is listed to stop	Yes, for the circuits it was wired to serve	Yes, subject to generation and storage
Which code governs the electrical design	The electrical standard the building code delegates to	Same	Same, plus dedicated stand-alone provisions we could not read
Storage required	No	Yes, and the storage provisions on listing, location and clearances apply	Yes, and the same provisions apply
What happens on a bad week	You buy from the grid, as always	You buy from the grid	You go without, or you run a generator. There is nothing else
Interconnection approval needed	Yes	Yes	No, because you are not connecting
Sized for	Annual consumption against annual generation	Annual consumption, plus the outage you want to survive	The worst period, not the average one

The listing rows come from the equipment provisions of the 2024 codes, read 3 September 2026. The rows on sizing and bad weeks are our reasoning about the design problem, not statements from any source, and are labelled as ours.

The last row is where off-grid stops being a variation and becomes a different discipline. A grid-connected system can be undersized and the consequence is a bill. An off-grid system that is undersized for the worst week of the year has no fallback except a generator or doing without.

The terms, several of which are listing categories rather than descriptions

Utility-interactive listing: An additional listing an inverter must carry to be connected to the grid. It is what the code requires and it is what makes the inverter stop when the network goes down. The single most important term on this page.
Islanding: A generator continuing to energise a section of network that has been isolated. Unintentional islanding is the hazard the utility-interactive listing prevents. Intentional islanding, done in a controlled way with the system separated from the network, is what a hybrid system does during an outage.
Stand-alone system: The code's own term for what the market calls off-grid. It has a dedicated provision within the solar article and a dedicated article among the special conditions, which tells you it is regulated as its own object rather than as a grid-tied system with the connection removed.
Grid-tied: Connected to the utility network, with no storage and no ability to run independently. Produces nothing during an outage, by design and by listing.
Hybrid: Grid-connected with storage and the equipment needed to run defined circuits when the network is down. Still requires the utility-interactive listing, because it is still a grid-connected system.
Neutral forming transformer: Equipment that establishes a neutral reference when the system is running separated from the grid. It is one of the functions now consolidated inside a single controller rather than sitting in its own enclosure.
Automatic transfer switch: The device that moves the protected circuits between the grid supply and the system supply. In current products it is typically inside the controller, which is why asking whether you need one separately produces confusing answers.

Why off-grid is harder than it sounds, stated as reasoning rather than as fact

We could not source a cost comparison, a sizing rule or a failure rate for off-grid systems, and we are not going to invent any. What follows is reasoning from the design problem, and we are labelling it that way so you can weigh it accordingly.

The grid is a battery of unlimited size that you pay for by the unit. That is what a grid-connected system is actually using it as. Remove it and every function it was performing has to be replaced with equipment you own: storage for the night, extra capacity for the cloudy week, and something that burns fuel for the stretch when neither is enough.

Sizing shifts from the average to the worst case. A grid-connected system that generates 80 percent of your annual consumption is a good system. An off-grid system that meets 80 percent of your needs leaves you without power for the other 20 percent, and that 20 percent is not spread evenly. It is concentrated in the darkest, coldest stretch of the year, which in most climates is also when consumption peaks.

Which means the array and the storage are sized for a period you experience once or twice a year, and are substantially oversized for the rest of it. That is not waste in a design sense, it is what reliability costs, but it explains why the equipment list is longer than people expect.

Almost every off-grid installation ends up with a fuel-burning generator, which brings its own set of risks that we cover in detail separately, including a federal record of carbon monoxide deaths and the finding that shutoff-equipped machines failed to trigger in testing while producing injurious indoor concentrations. If your off-grid plan includes a generator, read that before you plan where it goes.

And one code detail is worth knowing if you are considering repurposed batteries, which off-grid builders often do. The residential provision requires storage to be listed and labelled to UL 9540, with an exception permitting, where approved, repurposed unlisted battery systems from electric vehicles to be installed outdoors or in detached sheds located not less than five feet from exterior walls, property lines and public ways. Note what that exception is: outdoors or detached, at a distance, and only where approved. It is not permission to put them in the garage.

The honest case for each

Grid-tied is right for most houses connected to a reliable network. Fewest components, lowest cost, nothing to maintain beyond the array and the inverter, and no storage to degrade. Its one weakness is the outage, and if outages where you live are rare and short, that weakness may not be worth the cost of removing.

Hybrid is right when outages are frequent, long, or consequential. Medical equipment, a well pump, a home that is unlivable without heat, or a network that goes down repeatedly. It is also the right answer where the tariff rewards moving consumption between hours, which is a separate argument from backup and should be evaluated separately.

Off-grid is right when there is no grid, or when connecting to it costs more than replacing it. A remote property facing a large connection charge is the classic case, and it is a genuine one. Off-grid as a choice made at a property that already has a working connection is a much harder case to make, and it deserves a full accounting of the generator, the oversizing and the replacement cycle before anyone commits.

The question that sorts them is not how much solar you want. It is what you expect to happen when the sun is not shining and the grid is not there.

What to establish, in order

1
Decide whether outage performance is actually what you are buying
It is a distinct requirement with distinct equipment and cost. Bundling it into "I want solar" is how people end up disappointed by a system that was never designed to do it. Answer this before anything else.
2
Ask which listing the proposed inverter carries
Every inverter needs the baseline listing. A grid-connected one needs the utility-interaction listing on top. This is a question with a documented answer on the data sheet, and asking it tells you a great deal about whether the person quoting understands the distinction.
3
If you want outage performance, ask which circuits will run
Not whether the house will run. Which circuits. That decision is made when the quote is drawn and then physically wired, and changing it afterwards is electrical work rather than a setting.
4
Ask where the battery will go, against the location provisions
The residential code restricts where storage may be placed, requires separation between units, sets clearances from doors and windows, and imposes construction requirements on the enclosing space. Establish the location before the design, because it constrains everything downstream.
5
Ask for the clause number whenever you are told the code requires something
Most of the electrical rules are in a paywalled standard you cannot check casually. That makes an unverifiable "the code says" a weak answer. A clause number and an adopted edition can be checked with your building department.
6
For off-grid, size against your worst period rather than your annual total
This is our reasoning rather than a sourced rule, and it is the difference between a system that works and one that does not. Ask the designer to show you the calculation for the darkest week, not the annual average.
7
For off-grid, plan the generator before you need it
Almost every off-grid installation acquires one eventually. Where it goes, how it is fuelled and how its exhaust is handled are decisions with a documented safety record behind them, and they are much better made in advance than during an outage.
8
For off-grid, price the replacement cycle rather than the installation
Storage degrades and gets replaced. A comparison that weighs an off-grid installation against a utility connection charge, without the replacement cycle in it, is comparing a one-off cost to a recurring one.

What we could not verify

Any requirement, limit or wiring rule for stand-alone systems. The dedicated provision and the dedicated article both exist; their text is behind a paywall and we did not obtain it. We are telling you the structure exists and deliberately telling you nothing about what it says.

What hardware a grid-tied system needs added to run during an outage. No code text we could read and no federal document sets it out. What we can describe comes from manufacturer documentation for specific products.

Any cost comparison between the three. None is published in any primary source we read, and the variables are large enough that a general figure would be misleading even if one existed.

Any sizing rule for an off-grid system. The reasoning on this page about sizing to the worst period rather than the average is ours, presented as reasoning.

Whether your jurisdiction has adopted the editions quoted here. The clause text is from the 2024 editions as adopted in one state. Jurisdictions adopt on their own schedules and amend as they go, and one of the strongest findings elsewhere in our research is how easily a state amendment gets mistaken for model code.

Method and limitations

What was read

The equipment listing provisions of the 2024 residential and building codes, in full, for the listing requirements covering panels and modules, inverters, the additional utility-interaction requirement for grid-connected systems, mounting systems and building-integrated products.

The provision of the residential code delegating the electrical portion of solar photovoltaic systems to the national electrical standard, which is the reason so much of this subject is unreadable.

The residential code provisions on energy storage systems, for the listing requirement, the scope threshold, the separation between units, the permitted locations with their clearances and construction requirements, and the exception permitting repurposed electric vehicle batteries outdoors or in detached sheds at a stated distance where approved.

The section listings confirming that the electrical code contains a dedicated stand-alone systems provision within its solar article and a dedicated stand-alone systems article among its special conditions, and that parallel stand-alone identification requirements exist for fuel cells and wind.

What that limits

No electrical code text was read anywhere in this research. Every attempt returned a paywall stub. The existence of the stand-alone provisions is confirmed from section listings only, and nothing about their content appears on this page.

The building code text comes from the 2024 editions as adopted in one state. Adoption and amendment are local, and a state amendment can look exactly like model code to anyone reading a single jurisdiction.

The equipment description of what sits inside a modern controller comes from manufacturer documentation for particular products, not from any general requirement.

The reasoning about off-grid sizing, oversizing and the replacement cycle is ours, labelled throughout as reasoning rather than as sourced fact.

Questions

Why does my solar not work when the power goes out?

Because the code requires it not to. A grid-connected system must use an inverter listed for utility interaction, and that listing carries the behaviour that stops the inverter energising a line that has gone dead. It protects the people repairing the network from a house feeding power into a circuit they have isolated. Your panels are fine and your inverter is fine. It is doing exactly what it is certified to do.

What is the difference between grid-tied, hybrid and off-grid?

Grid-tied is connected to the network with no storage and produces nothing during an outage. Hybrid is connected to the network with storage and the equipment to run defined circuits when the grid is down, and it still needs the utility-interaction listing because it is still connected. Off-grid, which the code calls stand-alone, has no utility connection at all and is regulated as its own object, with a dedicated provision in the solar article and a dedicated article among the special conditions.

Can I add a battery later to get backup power?

Usually yes, and it is more involved than adding a box. The system has to be able to separate from the network in a controlled way, the circuits that will run have to be identified and physically wired to the protected side, and the storage has to go somewhere that satisfies the location, clearance and construction provisions in the residential code. Ask what the retrofit involves before assuming it is a later decision.

Do I need a transfer switch?

For a system that runs during an outage, yes, and in current products it is typically already inside the controller rather than being a separate box you buy. One manufacturer describes its controller as containing an inbuilt neutral forming transformer, microgrid interconnection device, automatic transfer switch and panel board in one enclosure. That consolidation is why the question often gets a confusing answer.

Is going off-grid cheaper than staying connected?

We could not find a primary source comparing them and we are not going to guess. What we can tell you is what changes: an off-grid system is sized against your worst period rather than your annual average, it needs storage for every night and extra capacity for every cloudy week, it almost always acquires a fuel-burning generator, and the storage has a replacement cycle. A comparison that weighs an installation cost against a connection charge without those in it is incomplete.

Why can I not just read the electrical code myself?

Because it is a copyrighted standard that is sold rather than published openly. The residential code delegates the electrical portion of solar systems to it entirely, so the rules on conductors, disconnects, overcurrent protection, rapid shutdown and stand-alone systems are all in a document you have to buy. The publisher offers a free read-only route behind registration, and your local building department holds the adopted edition. It is worth knowing that when someone tells you what the code requires.

What does listed for utility interaction actually mean?

It is an additional certification an inverter carries on top of the baseline inverter listing. It means the equipment has been evaluated for the behaviours required when it is connected to a live network, including ceasing to energise the line when the grid goes down. The code requires it for any grid-connected system, and an inverter without it may not be connected to the grid at all.

Can I use old electric vehicle batteries for off-grid storage?

The residential code requires energy storage to be listed and labelled to a storage system standard, with an exception permitting, where approved, repurposed unlisted battery systems from electric vehicles to be installed outdoors or in detached sheds located not less than five feet from exterior walls, property lines and public ways. Read that carefully: outdoors or detached, at a distance, and only where the building official approves it. It is not permission to put them in an attached garage.

If I am off-grid, do I still need permits and inspections?

The building code provisions on structure, on where storage may be located and on how it must be separated apply to any system, and the electrical design is still governed by the electrical standard. What you avoid is the interconnection process with a utility, because you are not connecting to one. Avoiding interconnection is not the same as avoiding regulation, and the stand-alone provisions exist precisely because the code treats these systems as a distinct case.

Should I go off-grid to avoid rising electricity prices?

That reasoning replaces a variable cost with a large fixed one plus a replacement cycle, and it usually adds a generator. Off-grid makes clear sense where there is no grid, or where the connection charge exceeds the cost of replacing it. Where a working connection already exists, the case is much harder and deserves a full accounting rather than a comparison of a monthly bill against an installation price.

Written and audited by

HyreSolar Research

Primary-source research, data analysis and fact checking

We are a research desk, not a sales floor. We read the statute, the tariff, the code section, the federal filing or the manufacturer data sheet ourselves, and we publish the figure with the document it came from and the date we retrieved it. Where a number cannot be traced to a primary source, we publish the shorter page and say what we could not verify. That rule has cost us whole sections, and it is the reason the rest can be trusted.

160: primary sources read and cited
220: figures with a retrieval date
115: federal and state government sources
66: researched pages published

How this desk works

Primary sources only. Statutes from the legislature’s own publishing system, federal data from the agency that collects it, code text from the adopted edition, manufacturer claims from the data sheet. We do not cite an article that cites a source; we go and read the source.
Every figure carries its provenance. A named document and the date we retrieved it, so you can check it and so you know how old it is. Retrieval dates are not decoration: an EIA rate from May is a different fact from an EIA rate from August.
We publish what we could not verify. Every research page carries a section naming the things we tried to establish and could not, and why. A paywalled standard, a state website that refused the request, a manufacturer that publishes no figure at all.
We separate measurement from modelling from our own reasoning, and label which is which on the page. A laboratory measurement, an assumption inside a modelling tool and our own inference are three different kinds of claim and they are never presented as one.
We do not sell solar, and we take no payment for placement, ranking or a favourable mention. Nobody buys a position on this site.

Data as of Building code text read on 3 September 2026. Authorship on this site is organisational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.

Sources & retrieval dates

2024 International Residential Code section R329.3.1 and 2024 International Building Code section 3111.3.1, equipment listings — Source for the requirement that photovoltaic panels and modules be listed and labelled in accordance with UL 1703 or with both UL 61730-1 and UL 61730-2, that inverters be listed and labelled in accordance with UL 1741, that systems connected to the utility grid shall use inverters listed for utility interaction, that mounting systems listed and labelled in accordance with UL 2703 be installed in accordance with the manufacturer instructions and their listings, and that building-integrated photovoltaic roof coverings and roof assemblies be listed and labelled in accordance with UL 7103. Read as adopted in Texas. Retrieved 3 September 2026.
2024 International Residential Code section R329.3, electrical requirements — Source for the provision that the electrical portion of solar photovoltaic systems shall be designed and installed in accordance with NFPA 70, which is the delegation that places the electrical rules governing a residential solar system inside a copyrighted standard that is sold rather than published openly. Retrieved 3 September 2026.
2024 International Residential Code section R330, energy storage systems — Source for the requirement that energy storage systems be listed and labelled in accordance with UL 9540, for the exception permitting, where approved, repurposed unlisted battery systems from electric vehicles to be installed outdoors or in detached sheds located not less than five feet from exterior walls, property lines and public ways, for the scope threshold, for the separation of not less than three feet between individual units except where the listing and installation instructions specify otherwise, and for the permitted locations with their clearances from doors and windows and their construction requirements. Retrieved 3 September 2026.
NFPA 70 sections on stand-alone systems, existence confirmed only — Cited solely to record that a dedicated stand-alone systems provision exists within the solar photovoltaic systems article and that a dedicated stand-alone systems article exists among the special conditions, and that parallel stand-alone identification requirements exist for fuel cells and for wind. The substantive text of these provisions was not obtained: every attempt returned a paywall stub, and no requirement, limit or wiring rule from them appears anywhere on this page. The publisher offers a free read-only access route behind registration. Retrieved 3 September 2026.

Deciding between a grid-tied system and one that runs in an outage?

Tell us how often your power goes out and what has to keep running when it does. We will tell you which of the three this actually is, and what the difference costs you in equipment.

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