Lesson 2.3Lesson 2.3 · The PV System
Grid-Tied, Off-Grid & Storage
At its far end every solar system meets one of three fates - it leans on the grid, it stands entirely alone on batteries, or it keeps the grid and adds storage - and that single choice reshapes the cost, the resilience and the very value of the energy the envelope makes
The sun sets every day, and buildings keep needing power after dark. What a solar system does about that - lean on the grid, stockpile in batteries, or both - is the choice that decides its cost, its resilience and how much its energy is actually worth.
A solar array has a fundamental awkwardness: it generates when the sun shines, which is rarely exactly when the building needs the power. The middle of the day is generous; the evening, when a home lights up and cooks, is dark. Every solar system must answer the question 'what happens to the mismatch?', and there are only three basic answers - which is why, at its far end, every system is one of three types.
The first and by far the most common is grid-tied: the system stays connected to the utility grid, which acts like a vast, always-available battery - it silently absorbs surplus solar when the building over-produces and supplies whatever the building needs when it under-produces. No on-site batteries are required; the grid does the balancing. The second is off-grid (stand-alone): there is no utility connection at all, so the system must carry the building entirely by itself, which means batteries to store daytime energy for night-time and cloudy spells, and careful sizing so it never runs dry. The third is hybrid: keep the grid connection *and* add batteries, blending the reliability of the grid with the self-sufficiency and backup that storage brings.
For most buildings, in India and worldwide, grid-tied is the sensible default - it is the cheapest, simplest and lets the grid do the hard balancing work. Off-grid earns its place mainly where there is no grid, or an unreliable one. Storage sits on a spectrum in between, adding real value (self-consumption, backup, resilience) at real cost. This lesson lays out the three types, their honest trade-offs, and what storage genuinely adds - while deferring, as ever, the binding electrical design, the connection rules and the net-metering specifics to the engineer, the utility/DISCOM and the codes.
Three types: grid-tied (grid balances, cheapest, dark in a cut), off-grid (batteries, no grid, costly), hybrid (grid + battery = self-consume + backup). Most buildings + BIPV = grid-tied.
Grid-tied - letting the grid do the balancing
The grid-tied system is the workhorse of solar, and understanding it well is most of this lesson. Its defining feature is simple: the building stays connected to the utility network, and the network absorbs and supplies the difference between what the array makes and what the building uses. When the sun is strong and the building is quiet, surplus flows out to the grid; when the building needs more than the array is giving - a cloudy hour, the evening, the night - the shortfall flows in from the grid. The grid behaves, in effect, like an enormous shared battery that the building can lean on without owning.
This is why grid-tied is so attractive: it needs no on-site storage, which removes the single most expensive and shortest-lived component from the system. It is the cheapest and simplest architecture, and it wastes nothing - surplus is exported rather than lost, and (under net-metering or similar arrangements) may be credited. For the overwhelming majority of buildings connected to a reasonable grid, it is the right default, and this course says so plainly.
It has two honest limitations. The first is the blackout behaviour: a standard grid-tied inverter must shut down when the grid fails, a safety feature called anti-islanding (so it cannot back-feed a 'dead' line and endanger a lineworker). The uncomfortable result is that a plain grid-tied system goes dark in a power cut *even in full sun* - it offers energy savings, not backup. The second is that the value of exported energy depends entirely on the rules: net metering (where exported units offset imported ones, sometimes near one-for-one) is generous; a lower feed-in rate or export cap is less so; and these rules are set by the utility and the regulator, vary by state and change over time (Module 8.2). So a grid-tied system's economics hinge on policy the designer does not control and must never guarantee.
For India, grid-tied dominates rooftop solar today, supported by advancing net-metering policy and intense cost sensitivity that disfavours expensive batteries where the grid is adequate. For BIPV, grid-tied is likewise the usual assumption - the envelope generates, the grid balances - with storage added only where its specific value justifies the cost.
Grid-tied: grid = giant shared battery. No storage, cheapest, wastes nothing. BUT goes dark in a blackout (anti-islanding). Export value = the utility's rules.
Off-grid - true autonomy, at a price
An off-grid, or stand-alone, system cuts the cord: there is no utility connection at all, so the building must be powered entirely by its own generation and storage. This changes everything about how the system is conceived, because there is no grid to lean on - no infinite battery to soak up surplus or cover a shortfall. The system must carry the building through every night, every cloudy day, every seasonal dip, on its own.
That makes two things essential. First, batteries - a bank large enough to store daytime energy for night-time use and to ride through periods of poor sun, sized around the building's demand and a chosen number of days of 'autonomy' (how long it must run without meaningful generation). Second, conservative, careful sizing of the whole system, with real margins, because running out is not an inconvenience the grid will quietly cover - it is the lights going off. Off-grid systems are therefore substantially more expensive and complex than grid-tied ones of the same generation, dominated by the cost, the space, the maintenance and the limited lifespan of the battery bank, and they usually demand disciplined energy use to stay within their means.
Where does off-grid earn its place? Chiefly where there is no grid, or reaching it is prohibitively expensive - remote sites, rural or hill locations far from lines, some isolated installations. In parts of India, off-grid and mini-grid solar has been genuinely transformative for communities beyond the reach of the network, providing power that simply would not otherwise exist. It is also chosen, occasionally, for deliberate independence or for critical loads that must never rely on the grid. But for a building that *has* a reasonable grid connection, going fully off-grid is usually the wrong, needlessly costly choice - the grid is a cheaper and more reliable 'battery' than one you buy and maintain.
The honest framing for a designer: off-grid is a specialist answer to the specific problem of *no grid*, not a greener or purer form of solar to aspire to by default. Its sizing, battery specification and safety are firmly engineering, and the autonomy calculation in particular must be done properly by an engineer for the real site and load - never estimated casually, because the penalty for getting it wrong is a building that goes dark.
Hybrid and storage - the value in between
Between the two extremes sits the hybrid system: keep the grid connection *and* add a battery. This is increasingly common as battery costs fall, because it blends the strengths of both - the grid's cheap, reliable balancing with storage's self-sufficiency and backup - and lets a building choose how much independence to buy. Understanding what a battery actually *adds* is the key, because storage is often over-sold.
Storage adds three things. First, self-consumption. Recall from 2.1 that a unit used on site is usually worth more than an exported one. A battery lets the building park midday surplus and spend it in the evening, converting low-value export into high-value self-consumption - especially valuable for an evening-peaking home, or wherever export is poorly paid. Second, backup. Unlike a plain grid-tied system, a properly configured hybrid can keep defined circuits running through a grid outage (safely islanded from the network), which is real resilience in places with frequent cuts. Third, flexibility - shifting energy in time to dodge expensive tariff periods, or to smooth demand.
But storage's costs are equally real and must be stated honestly. A battery is expensive, adding significantly to system cost. It is lossy - a few units go in for slightly fewer out (round-trip efficiency is below one). It has a finite life, degrading over years and thousands of cycles until it needs replacing, often before the panels do. It takes space and needs safe, ventilated, temperature-controlled installation (lithium-ion in particular has fire-safety requirements that are the engineer's domain). And it carries its own embodied impact (Module 8.3). So a battery must earn its place on grounds of self-consumption value, backup need or tariff arbitrage - not added reflexively because it feels more self-sufficient.
The honest position: for most grid-connected buildings, start grid-tied; add storage when the self-consumption economics, a genuine need for backup (frequent outages, critical loads), or tariff structures justify it - and size it to those specific needs. The sizing, battery chemistry, safety, fire protection and connection are binding engineering for the electrical engineer and the codes, and the payback depends on tariffs and rules set by the utility and regulator - never a designer's promise.
Battery adds: self-consumption (park midday sun for evening) + backup + flexibility. Costs: expensive, lossy, finite life, space, fire safety. Earn its place.
Choosing the type - and what it means for BIPV
How does a designer reason about which type fits, and what changes for a generating envelope? The decision tree is short and honest.
Is there a reasonable grid connection? If yes - as for most buildings in most Indian cities and towns - grid-tied is the default, and the real question becomes only whether to add storage. If no, or the grid is prohibitively far or unusable, off-grid (with batteries and conservative sizing) becomes necessary, and this is specialist engineering territory. Do you need backup? If the grid is present but unreliable (frequent, disruptive outages, or critical loads that must not fail), a hybrid system with storage buys resilience a plain grid-tied system cannot. Do the self-consumption economics favour storage? If export is poorly paid and the building's demand peaks after generation (evenings), a battery can be worth it; if net metering is generous and demand aligns with generation, the grid is a cheaper 'battery' and storage may not pay. These are the levers, and every one of them - grid quality, outage frequency, tariff and net-metering rules - is set by context and the utility, not by the designer.
For BIPV specifically, a few things follow. Because BIPV is usually part of a substantial, grid-connected building (often urban, often commercial or institutional), it is almost always grid-tied - the envelope generates and the grid balances. Storage is added where the building has critical loads, poor grid reliability, or a demand profile that rewards it. BIPV's spread of orientations can actually *help* the load-match: east and west facades generate morning and evening, broadening the generation curve toward the building's real demand and sometimes reducing the storage needed. And because BIPV buildings are large and long-lived, the choice of type interacts with the whole electrical strategy - plant space, protection, connection - that must be coordinated with the engineer from early design.
The designer's honest role across all three types is the same: understand the trade-offs well enough to shape the brief and the building (find plant and battery space, plan for backup if the site needs it, align demand with generation where possible), and defer the binding parts - system type sizing, battery specification and safety, anti-islanding and connection, and the net-metering and export rules - to the electrical engineer, the utility/DISCOM and the governing codes. Any figure for autonomy, self-consumption or payback here is illustrative and site-specific, never a guarantee.
Grid-tied
The default: connected, no on-site storage
The grid balances surplus and shortfall; cheapest and simplest, but a standard system shuts down in a blackout (anti-islanding) and export value follows the utility's rules. The usual BIPV assumption. Lessons 2.3, 8.2.
Off-grid (stand-alone)
No grid: batteries + conservative sizing
Must carry the building alone through nights and poor sun; needs battery autonomy and careful, engineer-sized margins. Earns its place mainly where there is no grid. Sizing is binding engineering. Wikipedia: Stand-alone power system.
Hybrid + storage
Grid kept, battery added
Adds self-consumption, backup and flexibility at real cost; batteries are expensive, lossy, finite-lived and need safe, ventilated, temperature-controlled space (lithium-ion fire safety). Size to a genuine need. Module 7.2.
Net metering & connection
What surplus is worth, and safe interconnection
Export value, net-metering terms, anti-islanding and grid connection are set by the utility/DISCOM and the codes (in India, CEA and state rules), vary and change - never a designer's guarantee. Module 8.2.
Workshop - pick the right system type for a building
The judgement this lesson builds is matching a system type to a building's grid, needs and demand shape. In this workshop you reason through the three types for a building you know and argue - honestly, pending the engineer - which fits and whether storage earns its place.
A building you know, a rough sense of its grid reliability and demand timing, this lesson's system-type diagram, and a notebook. No calculation - autonomy and payback sizing are the engineer's.
Goal: a reasoned grid-tied / off-grid / hybrid recommendation for one building Inputs: a building you know, a rough sense of its grid reliability and when it uses power + this lesson Time: ~45 minutes
- 1Check the grid: does this building have a reasonable grid connection, or is the grid absent or unreliable? This first answer largely sets the type - present and decent points to grid-tied; absent points to off-grid.
- 2Sketch the demand shape: roughly when does the building use most power - midday (like an office) or evening (like a home)? Compare that to when a solar array would generate.
- 3Test for storage value: given the demand shape, the export rules you assume, and the outage frequency, argue whether a battery would earn its place (self-consumption, backup, or neither) - and be honest if the grid is the cheaper 'battery' here.
- 4Note the space and safety implications: if you would add storage, where would the battery live safely (ventilated, temperature-controlled), and where would the plant go?
- 5Write a one-paragraph recommendation: the system type, whether storage is justified and why, and the honest caveats - all flagged as design reasoning to be sized and specified by the electrical engineer, with net-metering terms confirmed with the utility.
You’ll walk away with
A one-page recommendation for one building: the system type, an honest storage-or-not call with reasons, and space/safety notes - reasoning, not a specification, with sizing, battery safety and net-metering left to the engineer and utility.
Three altitudes on the same idea
Read the band that fits you — or all three.
The grid-tied / off-grid / hybrid choice reshapes cost, resilience and the value of the energy your envelope makes - so shape the brief around it, then defer the binding design. Grid-tied is the default for any building with a reasonable grid: cheapest, simplest, the grid balances surplus and shortfall, no batteries - but it goes dark in an outage (anti-islanding) and its export value depends on the utility's rules. Off-grid is a specialist answer to the absence of a grid, dominated by battery cost, space and conservative sizing. Hybrid keeps the grid and adds storage for self-consumption, backup and flexibility, at real cost, lossy and finite-lived. For BIPV - usually a large, grid-connected building - grid-tied is almost always the assumption, with storage where backup, poor grid reliability or self-consumption economics justify it, and a spread of facade orientations can broaden generation to match demand. Own the space-planning, backup brief and demand-generation alignment; defer type sizing, battery safety, connection and net-metering to the engineer, the utility and the codes.
System type and storage decide whether the interior keeps power in an outage, how much of its own solar it uses, and what plant and battery space the building must hold. A plain grid-tied building goes dark in a cut despite the sun; if the interiors serve critical functions or the local grid is unreliable, a hybrid system with a battery can keep defined circuits alive - a real comfort and safety consideration you help brief. Storage also raises self-consumption, which rewards interiors whose lighting, plug and cooling loads can be shifted toward the solar hours. Batteries need safe, ventilated, temperature-controlled space (lithium-ion has fire-safety rules), a coordination that touches your plans. You will not size the system or specify the battery - that is binding engineering - but understanding the three types lets you brief backup honestly, align interior loads with generation, and make room for the plant that a generating, resilient building needs.
Learn the three system types and their trade-offs and you can reason about almost any solar project. Grid-tied leans on the utility as an infinite shared battery: cheapest, simplest, no storage, but dark in a blackout (anti-islanding) and dependent on export rules. Off-grid stands alone on batteries and conservative sizing - essential where there is no grid, but expensive and complex, not a purer solar to aspire to by default. Hybrid keeps the grid and adds storage, which genuinely adds self-consumption, backup and flexibility but is expensive, lossy, finite-lived and space-hungry, so it must earn its place. Understand why most buildings are grid-tied, why storage is often over-sold, and how a spread of orientations can broaden generation to match demand. You are not expected to size systems or specify batteries - that binding work is the engineer's, and the net-metering rules are the utility's - but to weigh the trade-offs clearly and honestly.
“Going off-grid with batteries is the greenest, most independent way to do solar, and every serious solar building should aim for it. A grid-tied system is a compromise, and adding a big battery always makes a building more sustainable and more resilient.”
Do it yourself
No tools needed - reason it through.
- 1Explain how a grid-tied system uses the grid to balance surplus and shortfall, and why it still goes dark in a blackout.
- 2When does an off-grid system genuinely earn its place, and why is it usually the wrong choice where a decent grid exists?
- 3What three things does a battery actually add, and what are its honest costs?
- 4Walk through the short decision tree for choosing grid-tied, off-grid or hybrid for a given building.
- 5Why is BIPV almost always grid-tied, and which parts of the system-type decision must be deferred to the engineer and the utility?
The one line to carry out
Peer-reviewed journals & authoritative standards
- 01Grid-connected photovoltaic power system — Wikipedia - Grid-connected photovoltaic power system, 2026.
- 02Stand-alone power system — Wikipedia - Stand-alone power system, 2026.
- 03Grid energy storage — Wikipedia - Grid energy storage, 2026.
- 04Net metering — Wikipedia - Net metering, 2026.
- 05Lithium-ion battery — Wikipedia - Lithium-ion battery, 2026.
We now know the whole system - anatomy, inverter and balance of system, and how it connects at the far end. The last question of the module is the honest one: how big should it be, and how much will it really generate? Next we tackle sizing and yield, and why nameplate is never delivered energy.
The author
Amogh N P
Architect, interior designer, and creative polymath. Studio Matrx began in his notebooks — his vision of design made honest, useful, and open to everyone. Its Academy is written and taught in his memory, and free, forever.
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