Skip to content
WattCurious

On-Grid vs Off-Grid vs Hybrid Solar Systems

Updated 21 September 20267 min readSolar Energy

The panels are the same in all three. What differs is what the system leans on when generation and demand do not match, which is most of the time. A grid-tied system leans on the grid, an off-grid system leans on a battery it had to size for the worst week of the year, and a hybrid leans on both and has to decide, automatically and quickly, which one it is using.

Key takeaways

  • A grid-tied inverter disconnects during an outage by design, to keep it from energising a line that someone may be working on.
  • Off-grid systems are sized against the worst month, so they spend most of the year with more capacity than they can use.
  • A hybrid is not a grid-tied system with a battery bolted on: it needs a transfer arrangement and a defined set of backup circuits.
  • The battery in a hybrid does two different jobs — shifting energy day to day, and carrying the house through an outage — and they pull its sizing in opposite directions.
  • The three architectures fail differently, and how a system behaves when something goes wrong is usually the real basis for choosing.
On this page
  1. One question, three answers
  2. Grid-tied, and why it goes dark
  3. Off-grid: you are the grid
  4. Hybrid: both, and a decision
  5. What each has to be sized for
  6. They fail differently

One question, three answers

Generation and demand almost never match. The sun peaks at midday and households do not; the sun sets and the evening starts. So every photovoltaic system needs somewhere to put a surplus and somewhere to draw a shortfall, and the three architectures are simply three answers to that.

Three architectures for the same arrayThree system diagrams. The grid-tied system runs from array to inverter to the house loads, with the grid connected as both a sink for surplus and a source for shortfall, and no battery. The off-grid system runs from array to charge controller to a battery and an inverter serving the loads, with a generator as optional backup and no grid connection at all. The hybrid system has both: array, battery and inverter, with a grid connection and a transfer arrangement that separates a set of backup circuits from the rest of the house.Grid-tiedarrayinverterloadsgridsurplus out, shortfall in —the grid is both, and there is no batteryfewest conversions, highest efficiency · and nothing works when the grid is downOff-gridarraychargecontrollerbatteryinverterloadsgeneratorno grid at all · sized against the worst month · the generator covers the tailHybridarrayinverterbatterytransferswitchbackup circuitsthe restgridboth sources, and something that has to decide between them — which is where nearly all the extra complexity lives
The same array in all three. What changes is what absorbs a surplus and what covers a shortfall — and, in the hybrid, who decides.

Grid-tied uses the grid as both. Off-grid uses a battery for both, with a generator for the cases the battery cannot cover. Hybrid uses both and has to arbitrate between them, which is where nearly all of its additional complexity comes from. Where a surplus actually ends up in each case is the subject of what happens to excess solar energy.

Grid-tied, and why it goes dark

The grid-tied case is the simplest electrically and the most surprising behaviourally. No battery, the fewest conversions, and the highest efficiency of the three — and it stops producing the moment the grid fails, even at noon on a clear day.

Anti-islanding: why a grid-tied array stops in an outageTwo states of a grid-tied connection. In normal operation the inverter synchronises to the grid's voltage and frequency and feeds power to the house and out to the network. In an outage the network is de-energised and a utility crew is working on the line; the inverter detects the loss of grid within a fraction of a second and opens, so no power flows out to the conductors. A note explains that an inverter which kept running would energise lines the crew expects to be dead.Normal — the inverter follows the gridOutage — the inverter opensarrayinverterhousesynchronised to the grid'svoltage and frequencydistribution line — livePower flows to the house and outto the network.arrayinverterhouseopens within a fractionof a seconddistribution line — de-energisedsomeone is working on itNothing flows out. The array isproducing nothing at all.The inverter is not protecting itselfA grid-following inverter matches the voltage and frequency it sees. Remove the reference and it has nothingto follow — and it must not carry on, because it would energise a section the crew has isolated.This is anti-islanding, and it has nothing to do with the panels, the battery or the weather.
Anti-islanding. The inverter is not protecting itself — it is protecting whoever is working on the line outside.

A grid-following inverter does exactly what its name says: it matches the voltage and frequency it sees and pushes current in phase with them. Remove the reference and it has nothing to follow, so it stops. It also *must* stop, because an inverter that carried on would back-feed a section of network that crews have isolated and expect to be dead.

That is the trade a grid-tied system makes, and it is a good one for most sites: maximum simplicity and efficiency, at the price of having no independent supply at all.

Off-grid: you are the grid

Remove the grid and every job it was doing becomes yours. The inverter now has to establish voltage and frequency rather than follow them, the battery has to cover every night and every cloudy stretch, and the sizing has to assume the worst.

Sized for the worst month, oversized for every otherA chart of monthly available generation against a flat load line for an off-grid site. The system is sized so that even the worst month clears the load, which leaves a very large unusable surplus through the summer. Alongside, a second chart shows the same site sized for the annual average instead, meeting the load for most of the year but falling short through several winter months.Sized for the worst month — it always worksJanDecsurplus that cannot be usedEvery month clears the load, including the worst one.The price is an enormous unusable surplus for most of the year.Sized for the average — it fails in winterJanDecshort hereand hereWorks for most of the year, and not when it matters.Off-grid, "most of the year" is not an acceptable answer.The oversizing is structural, not a flawA system that must work in the worst month is oversized for every other one, which is why an off-grid arrayspends sunny afternoons curtailed with a full battery and nowhere to put the rest.A generator is the honest answer to the tail: it covers the rare case directly, so everything else can be sized for ordinary weather.Illustrative monthly shape for one site in one hemisphere; the pattern reverses across the equator.
Sizing for the worst month is what makes an off-grid system work — and what leaves it with far more capacity than it can use for most of the year.

The consequence is structural rather than a flaw. A system that must work in the worst month is oversized for every other month, which is why an off-grid array spends sunny afternoons curtailed with a full battery. The method for arriving at those numbers is the whole of off-grid load calculation, and the depth the battery is cycled to is set by the trade in depth of discharge.

A generator is the honest answer to the tail. Sizing storage for a once-in-five-years fortnight of weather means paying for capacity that will sit idle for years; a generator covers that case directly and lets everything else be sized for ordinary conditions.

Hybrid: both, and a decision

A hybrid has a grid connection and a battery, and the interesting part is neither — it is the arrangement that switches between them.

What the transfer arrangement doesA hybrid system drawn around a transfer arrangement in two states. In normal operation the grid supplies the whole house and the battery shifts energy through the day. When the grid fails, the transfer isolates the house from the network and the inverter forms its own supply, but only for a defined set of backup circuits such as lighting and refrigeration, while the remaining circuits stay unpowered. A note marks that the backup set has to be chosen at installation because the inverter and battery can only carry so much at once.Grid present — the inverter followsarrayinverterbatterytransferbackup circuitsthe restgridthe grid supplies the whole house; the battery shifts energy through the dayGrid gone — the transfer isolates, the inverter formsarrayinverterbatterytransferbackup circuitsthe restgridisolated from the network · the inverter establishes its own voltage and frequency · only the backup set is carriedTwo modes, not oneConnected, the inverter follows the grid's voltageand frequency. Islanded, it has to establish them —a genuinely different control problem, and thereason these inverters are built differently.The backup set is chosen at installationThe battery cannot carry the whole house, so asubset of circuits is designated — lighting,refrigeration, a few sockets — and everythingelse goes dark exactly as a grid-tied house would.
The transfer separates the house from the network, and separates the circuits worth carrying from the ones that would empty the battery by morning.

Two things make this harder than it sounds. The inverter has to form a grid when islanded and follow one when connected, which are different modes with different control problems. And the battery cannot carry the whole house — so a subset of circuits is designated as backup at installation, and everything else goes dark exactly as it would in a grid-tied system.

The battery is also being asked to do two jobs at once. Daily shifting wants a battery cycled often and not very deeply. Outage backup wants reserve held in hand, unused, for an event that may not come this year. Those pull sizing in opposite directions, and the resolution is a reserve threshold: the system cycles the top portion daily and refuses to go below a floor it keeps for outages.

What each has to be sized for

The architectures differ less in components than in what governs their size.

What sets the size of each part
Grid-tiedOff-gridHybrid
Array sized byAnnual energy targetThe worst monthAnnual target, plus backup demand
Battery sized byNone fittedDays of autonomyDaily shifting, plus a reserve floor
Inverter sized byArray peakPeak load and surgeBoth, plus backup circuits
Surplus goes toThe gridCurtailed once the battery is fullBattery, then grid, then curtailed
Shortfall covered byThe gridBattery, then generatorGrid, or battery when islanded
During an outageNothing worksUnaffectedBackup circuits only
Conversion stagesFewestMostMost, and mode-dependent

Design relationships rather than recommendations. Every one of these is a property of the site and the load, and the same house on the same roof can justify any of the three.

The row that decides most installations is the second-to-last. Everything else is a matter of degree; that one is a difference in kind.

They fail differently

Choosing between them is usually a question about failure rather than about efficiency, because the components are similar and the behaviours are not.

Three architectures, three ways of going wrongThree failure profiles. The grid-tied system shows a single total stop that is obvious the same day and depends on a professionally maintained network. The off-grid system shows a gradual decline through degraded cells, a derating controller and a load that grew, none of it visible until a bad week arrives. The hybrid system shows both, plus the transfer arrangement highlighted as the component that matters most and is exercised least, because it only operates when the grid fails.How each one lets you downGrid-tiedone total stop, the same dayone accessible box to replace→ total dependence, on something professionally maintainedOff-griddegraded cells, a derating controller,a load that grew since the table→ nothing announces itself until a bad week arrivesHybridboth of the above — plus one more→ the transfer itself: the component that matters most and is exercised leastWhich failure would you rather have, and would you notice it?That is the honest basis for choosing — not which is most efficient, because grid-tied is, comfortably.Systems that test their transfer periodically find out on their own terms. Systems that do not find out during the outage.
Loud and total, quiet and gradual, or both plus a switch that is only tested by the event it exists for.

A grid-tied system's failures are mostly single and visible: the inverter stops and the system stops, which is obvious the same day. Its dependence is total but on something professionally maintained.

An off-grid system fails gradually and privately. A loop of degraded cells, a charge controller derating, a load that grew since the table was written — none announces itself until a bad week arrives and the lights do not come back. This is why an off-grid system needs its output watched in a way a grid-tied one does not, and why the diagnostic sequence in why a system produces less than expected matters more here than anywhere else.

A hybrid adds a failure mode the others do not have: the transfer itself. The one component that matters most is the one exercised least, because it only operates when the grid goes down. Systems that test their transfer periodically find this out on their own terms; systems that do not find out during the outage.

Which is the honest basis for choosing. Not which is most efficient — grid-tied is, comfortably — but which failure you would rather have, and which one you are equipped to notice.

Frequently asked questions

Why does my grid-tied system stop working in a power cut?

Because it is required to. An inverter that kept feeding the network during an outage would energise lines that utility crews expect to be dead, so grid-tied inverters continuously check for the grid and shut down within a fraction of a second if it disappears. This is called anti-islanding, and it has nothing to do with the panels or the weather.

Can I add a battery later and get backup?

Adding storage to a grid-tied system gives you energy shifting, but backup during an outage needs more than a battery — it needs a way to disconnect from the grid and form its own supply, plus a decision about which circuits it carries. That is a change of architecture rather than an addition, and it is much easier when it was planned for.

Do off-grid systems need a generator?

Many include one, not because the design failed but because it is the sensible answer to a rare problem. Sizing a battery and array for the worst imaginable week means paying for capacity that sits unused for years. A generator covers that tail directly, and lets everything else be sized for ordinary conditions.

What is a black start?

Bringing a system up from nothing, with no external supply to synchronise to. A grid-tied inverter never does this — it follows the grid's voltage and frequency. An off-grid or hybrid inverter has to establish them itself, which is a genuinely different job and the reason those inverters are built differently.

Which architecture is most efficient?

Grid-tied, because energy makes the fewest conversions: panel to inverter to load, with the grid absorbing anything left. Every route through a battery costs a round trip, and every additional conversion stage costs a little more. Efficiency is rarely the deciding factor, though — availability usually is.

Sources

Named organisations whose published material underpins this article. Where no link is given, the source is named rather than linked.

Editorial Team

Research, drafting and review

Articles are drafted from primary engineering and physics references with AI-assisted tools, then reviewed and fact-checked line by line by a human editor before publication. We publish explanations, not recommendations: no products, no pricing, no country-specific rules, and no invented author personas.

Last reviewed 21 September 2026. How we research and review