One of the most persistent misconceptions in Indian residential solar is the belief that a rooftop system keeps the lights on during a power cut. It does not — at least not by default. A standard grid-tied (on-grid) rooftop installation is designed by national safety code to shut down the moment the grid goes down, even when the sun is shining and your panels are producing peak output. The feature responsible is called anti-islanding, mandated under IS 16221 and IEEE 1547, and it exists to protect the lineman repairing the fault on the pole outside your home. Roughly 70% of new residential solar buyers we speak to in 2026 still assume the opposite — that solar means backup. This guide fixes that mental model.
The good news: solar can absolutely run your home during power cuts — but only in specific configurations. Either you add a battery and a hybrid inverter to your rooftop array, you go fully off-grid, or you pair on-grid solar with a diesel generator (DG) for a hybrid resilience setup. Each option has very different costs, payback periods, and use cases, and the right answer depends almost entirely on how many outage hours your DISCOM (distribution company) inflicts on you every month.
Direct answer. A pure on-grid rooftop solar system does not work during a power cut — the inverter shuts off within 200 milliseconds under IS 16221 anti-islanding protection. Only a hybrid solar + battery system (₹3–4 lakh extra for a 5 kWh setup) keeps loads running through outages. Off-grid is rare for urban homes due to battery cost. The most common Indian backup pairing remains on-grid solar plus a small diesel generator (DG) running ₹15–25 per kWh on fuel.
If your household tolerates 5+ hours of outage per month, hybrid solar economics make sense. If your outages are rare and short, on-grid plus a small DG is cheaper. The rest of this guide breaks down the four configurations, the standards, the real costs, and how Heaven Green Energy designs each option for residential homes across India.
Why On-Grid Solar Shuts Off When the Grid Is Down
A grid-tied (on-grid) solar inverter is, by design, a grid-following device. It synchronises its output voltage, frequency, and phase to the utility grid sitting on the other side of your import-export meter. When the grid is present, the inverter pushes excess solar power outward and lets the grid act as an infinite “battery.” When the grid disappears — whether from a tripped feeder, a substation fault, or a maintenance shutdown — the inverter has nothing to synchronise to. Within a few hundred milliseconds, it senses the loss of grid voltage and frequency reference and disconnects itself from the AC output.
This behaviour is not a software accident. It is mandated by the Central Electricity Authority (CEA) Technical Standards for Connectivity of Distributed Generation Resources, which require every grid-interactive solar inverter sold in India to comply with IS 16221 Part 2 and the international parent standard, IEEE 1547. Both standards specify the same thing: an unintentional island — a portion of the grid energised by a distributed generator while the rest of the feeder is dead — is dangerous. A lineman climbing the pole to repair a fault assumes the line is dead because the substation breaker is open. If your rooftop solar continued to backfeed the line, the lineman could be electrocuted.
So the inverter shuts off. Your panels are still generating DC current under sunlight, but the inverter refuses to convert it to AC and refuses to energise your house wiring. Your lights, fans, and air conditioner go dark exactly as if the solar system did not exist. The instant the grid comes back, the inverter waits a programmed 5-minute reconnection window (per IEEE 1547) to confirm the grid is stable, then re-synchronises and resumes export. This is why a pure on-grid system is sometimes described as a “bill killer, not a backup” — it is engineered for export revenue, not resilience.
For a deeper comparison of these configurations side-by-side, see our companion guide on on-grid vs off-grid vs hybrid solar systems in Gujarat.
The 4-Configuration Power-Cut Resilience Map
We call this framework The 4-Configuration Power-Cut Resilience Map — a single decision matrix we walk every residential customer through during their consultation. The four configurations are the only physically distinct ways you can pair solar with backup in India, and choosing between them is the single most consequential decision in the entire solar buying process for any household that experiences outages.
The map lays out the four against four variables: behaviour during a power cut, capital cost premium over a baseline grid-tied system, running cost, and ideal buyer profile. Pick the row that matches your monthly outage tolerance and budget, then talk to a designer about sizing.
| Configuration | During Power Cut | Capex Premium | Running Cost | Best For |
|---|---|---|---|---|
| On-grid only | No output — inverter shuts off | ₹0 (baseline) | ₹0 | Stable grid, bill-killer goal |
| Hybrid (on-grid + battery) | Solar + battery powers home | ₹3–4 lakh (5 kWh LFP) | Battery replacement at year 10–15 | 5+ outage hours / month |
| Off-grid only | Self-sufficient; no grid dependency | ₹5–8 lakh (10 kWh + larger inverter) | High battery cycling cost | Remote farms, no grid access |
| On-grid + DG backup | DG runs independently during cuts | ₹60–95K (5 kVA DG) | ₹15–25 / kWh diesel + service | Rare outages, low capex budget |
The on-grid baseline is what 90% of urban Indian households install today — it captures the PM Suryaghar subsidy of ₹78,000, hits payback in 3–5 years, and treats power cuts as a non-event because the household has either learned to tolerate them or has a separate inverter-battery for essential loads. The hybrid configuration is the structurally correct answer for outage-prone states. The off-grid configuration is genuinely rare for residences — it makes financial sense only when grid extension itself would cost lakhs. The on-grid plus DG configuration is the most common compromise in Tier-2 and Tier-3 cities, and it remains a perfectly defensible choice for any household where outages are infrequent.
The remaining sections drill into each configuration in turn.
Anti-Islanding Standard — IS 16221 and IEEE 1547
If you take only one technical concept from this guide, make it this one: anti-islanding is a feature, not a bug, and it is non-negotiable for any grid-connected inverter sold in India. The standard is published by the Bureau of Indian Standards (BIS) as IS 16221 Part 2, which mirrors the international IEEE 1547 standard for distributed energy resource interconnection. Both are referenced by the Ministry of New and Renewable Energy (MNRE) in its inverter empanelment criteria, and your DISCOM verifies compliance during the net meter inspection.
The standard sets explicit trip thresholds. If grid voltage drifts outside a 88%–110% band around nominal, or if frequency drifts outside 47.5–51.5 Hz, the inverter must disconnect within a defined time window. For a hard grid loss — the substation breaker opens — disconnection must happen within 200 milliseconds. Reconnection is intentionally slowed: the inverter must wait a minimum of 5 minutes after the grid returns and stabilises before it resumes export. This delay prevents a “yo-yo” effect where multiple solar inverters across a feeder repeatedly reconnect and trip during an unstable restoration.
| Rule | Threshold | Source |
|---|---|---|
| Disconnect on grid loss | ≤ 200 ms | IS 16221 Part 2 / IEEE 1547 |
| Voltage trip band | 88%–110% nominal | IEEE 1547 Clause 4.2 |
| Frequency trip band | 47.5–51.5 Hz | CEA Connectivity Standard 2019 |
| Reconnection delay | ≥ 5 minutes after grid stable | IEEE 1547 Clause 4.10 |
| Applicable to | All grid-tied PV inverters | MNRE empanelment rules |
There are inverter modes that defeat anti-islanding intentionally — microgrid or island-capable modes — but they are available only on hybrid inverters with a battery present. The battery acts as the voltage and frequency reference that the inverter synchronises to during an island. Without a battery, an island-capable mode is unsafe and not certified for residential use. This is the engineering reason a battery is required for backup; software alone cannot legally provide it.
Hybrid Solar + Battery Setup — Real Cost in 2026
A hybrid system replaces three things in a standard on-grid design: the inverter, the wiring topology, and the addition of a battery bank. The hybrid inverter is a dual-purpose unit — it can export to the grid like a regular grid-tied inverter, and it can operate in island mode using the battery as a reference when the grid is absent. Popular hybrid inverter brands in the Indian residential market in 2026 include Deye, Growatt, Sungrow, Luminous Hybrid, and Microtek. A 5 kVA hybrid inverter sits in the ₹50,000–₹70,000 range, roughly double a comparable on-grid-only inverter.
The battery is where the real money goes. For 2026 residential installations, we recommend lithium iron phosphate (LFP) chemistry exclusively. LFP cells have a thermal runaway temperature above 270°C compared to roughly 150°C for NMC chemistries, making them dramatically safer for indoor installation. A 5 kWh LFP battery pack with an integrated battery management system (BMS) runs ₹2.0–₹2.5 lakh installed, including the wall-mount cabinet, communications cabling, and the safety isolators required by your inspector. For a head-to-head on chemistry, see lithium vs lead-acid for solar homes and the deeper lithium vs lead-acid detailed 2026 breakdown.
| Hybrid System Tier | Solar (kWp) | Battery (kWh) | Hybrid Inverter | Total Installed | Backup Window |
|---|---|---|---|---|---|
| Light backup | 3 kWp | 5 kWh LFP | 5 kVA Deye / Growatt | ₹4.5–₹5.5 lakh | 6–10 hr essentials |
| Standard home | 5 kWp | 7.5 kWh LFP | 7.5 kVA Sungrow | ₹6.5–₹7.5 lakh | 8–12 hr full home |
| Whole-home | 7 kWp | 10 kWh LFP | 10 kVA Deye | ₹8.5–₹10 lakh | 10–14 hr full home |
| Heavy backup | 10 kWp | 15 kWh LFP | 12 kVA dual | ₹13–₹15 lakh | 14–18 hr inc. AC |
The headline number for a typical Indian household is that hybrid adds ₹3–4 lakh on top of a baseline 5 kWp on-grid system. That premium is the cost of resilience. Payback on the battery portion alone runs 6–10 years if you use the battery purely to avoid power cuts; it shortens to 5–7 years if you also use the battery to arbitrage daytime solar against evening tariffs (time-of-use arbitrage), which is increasingly relevant under the CEA’s revised retail tariff framework being rolled out across DISCOMs. If you already own an on-grid system and want to retrofit a battery, read our practical walkthrough on how to add a battery to an existing solar system.
Get a free hybrid sizing review. Send us your last electricity bill and a rough count of how many outage hours your area sees per month. We will run the battery sizing math and quote the LFP plus hybrid inverter premium for your home. Get your free quote →
Off-Grid Solar — Why It’s Rare for Indian Homes
Off-grid solar removes the grid from the picture entirely. No import-export meter, no DISCOM application, no net metering paperwork, no PM Suryaghar subsidy. The household lives on solar plus a substantially oversized battery bank, with a backup generator or extended battery autonomy for monsoon days when irradiance collapses for a week at a time. On paper, it is the purest expression of energy independence. In practice, it is brutally expensive for any household that has a grid connection already wired to the boundary wall.
The mathematics are unkind. A typical 3-BHK home consumes 350–500 kWh per month, or roughly 12–17 kWh per day. To survive a 3-day monsoon stretch without sun, you need at least 40 kWh of usable battery capacity, which (at LFP) means a 50 kWh nameplate bank — roughly ₹18–22 lakh in battery alone. You also need an inverter sized for peak load (likely 10–15 kVA), plus a solar array large enough to recharge the bank fully on a sunny day. Total installed cost for a competent off-grid 5 kWp + 50 kWh system sits in the ₹25–32 lakh range. That is 8–10× the cost of an equivalent on-grid system.
Off-grid only makes financial sense in two scenarios. The first is remote agricultural land where the grid extension quote from your DISCOM exceeds ₹10–15 lakh — bringing a high-tension line across two kilometres of field is not cheap. The second is specialised installations like temple complexes, forest department guesthouses, or border outposts where grid presence is impossible or politically constrained. For a normal urban or peri-urban Indian home with a working DISCOM connection, off-grid is the wrong answer. A hybrid system gives you 90% of the resilience benefit at 30% of the cost.
This is why our off-grid pipeline at Heaven Green Energy is dominated by farms, dairies, and pump houses rather than residential rooftops.
DG Backup with On-Grid Solar — Most Common Indian Setup
If you walk through any Tier-2 city neighbourhood with a higher-than-average outage profile — Patna, Lucknow, Bhubaneswar, Kanpur, Asansol — you will see the dominant resilience pattern emerging in 2026: an on-grid rooftop solar system on the roof, and a 3–5 kVA portable or fixed diesel generator (DG) in the back garden or stilt parking. The two systems do not talk to each other. They live in parallel. The solar runs the home during the day under the grid; the DG fires up manually (or via an auto-transfer switch, ATS) when the grid drops.
The economics are the easiest to defend if your outages are short and infrequent. A 5 kVA Honda, Kirloskar, or Mahindra DG retails for ₹50,000–₹80,000 installed, with an annual service contract of ₹3,000–₹5,000 and fuel running ₹15–25 per kWh depending on diesel price and engine efficiency. Compare that to a hybrid system’s ₹3–4 lakh capex premium and you can see why a household with five short outages a month picks the DG: the breakeven on the hybrid premium against avoided DG fuel does not arrive until year 8–11.
| DG Spec | Capex | Annual Service | Fuel Cost | Verdict |
|---|---|---|---|---|
| 2.5 kVA portable petrol | ₹25–35K | ₹2,000 | ₹30–40 / kWh | Emergency only |
| 5 kVA diesel (Honda/Kirloskar) | ₹55–75K | ₹3,500 | ₹18–22 / kWh | Tier-2 residential standard |
| 7.5 kVA diesel fixed | ₹85K–₹1.1L | ₹5,000 | ₹15–20 / kWh | Large homes, multiple ACs |
| 10 kVA diesel with ATS | ₹1.2–₹1.5L | ₹6,500 | ₹15–18 / kWh | Whole-home automation |
There are real downsides to DG that the price-per-kWh number hides: noise (75–90 dB at one metre), exhaust fumes that violate the Central Pollution Control Board’s residential air quality norms, the inconvenience of refuelling, and the maintenance overhead of an oil change every 100 operating hours. None of these are deal-breakers for a household using the DG for 5–15 hours a month, but they become painful at 30+ hours a month — which is exactly the threshold where the hybrid system overtakes the DG on total cost of ownership.
For households considering the more limited option of a regular inverter-battery instead of either a hybrid or a DG, our comparison guide on solar vs inverter battery walks through the trade-offs.
Real Power-Cut Hours in India by State — 2025 Data
The single biggest driver of “should I add a battery?” is your local outage profile, and that varies wildly across India. The data below blends CEA’s State Power Sector Reports, Prayas Energy Group’s electricity supply monitoring, and our own field service tickets across the states where we operate. These are residential averages — commercial and industrial outage profiles differ.
| State | Avg Outage Hours / Month | Configuration We Recommend |
|---|---|---|
| West Bengal (rural) | 30+ | Hybrid 7.5 kWh battery |
| Bihar (Tier-2/3) | 25+ | Hybrid 7.5 kWh battery |
| Uttar Pradesh (rural) | 20+ | Hybrid 5–7.5 kWh battery |
| Odisha (coastal) | 12–18 | Hybrid 5 kWh battery |
| Karnataka | 5–7 | On-grid + 3 kVA DG |
| Tamil Nadu | 5–7 | On-grid + 3 kVA DG |
| Maharashtra (urban) | 5–8 | On-grid + 5 kVA DG |
| Gujarat | 3–5 | On-grid only |
| Delhi NCR | 2–4 | On-grid only |
| Rajasthan (JVVNL belt) | 4–6 | On-grid + small DG |
Heaven Green Energy’s installation pattern follows this data precisely. In high-outage states, hybrid systems comprise 60–70% of our 2026 residential book. In Gujarat and Delhi NCR, hybrids fall to under 10% — the grid is reliable enough that customers prioritise faster payback over backup. Your DISCOM’s published Average Interruption Duration Index (SAIDI) is a useful starting point; ask your DISCOM customer service for it before committing to a configuration.
Common Misunderstandings About Solar + Power Cuts
We collected the eight recurring confusions from our 2025–26 consultation calls. If any of these matches what you currently believe about solar and backup, the right next step is a 15-minute call with a designer rather than an order placed online.
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1
"My solar will keep my lights on when the grid trips." Only true if you bought a hybrid system with a battery. A pure on-grid system shuts off in under 200 ms by IS 16221 mandate.
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2
"I'll just add a battery later if I need backup." Possible, but a grid-tied inverter cannot use a battery — you must also replace the inverter with a hybrid unit, which adds ₹50–70K beyond the battery itself.
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3
"Off-grid is more independent so it's better." Off-grid costs 8–10× a comparable on-grid system for an urban home. Hybrid gives 90% of the resilience benefit at 30% of the cost.
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4
"My UPS will handle solar backup automatically." A consumer UPS is sized for 30–60 minutes of computer-class load. It cannot replace a hybrid inverter and cannot interface with rooftop solar at scale.
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5
"PM Suryaghar subsidises the battery too." The ₹78,000 subsidy covers grid-connected PV only. Batteries are paid entirely by the homeowner; budget separately.
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6
"Anti-islanding can be disabled by the installer." No legitimate installer will disable it. Doing so violates IS 16221 and voids the DISCOM net metering agreement. It is also a criminal liability if a lineman is injured.
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7
"DG and solar can run in parallel automatically." Only if the DG has a synchronisation panel certified to IEEE 1547 — most residential DGs do not. Without sync, the inverter sees the DG output as a grid and may trip on frequency.
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8
"Hybrid batteries run my air conditioner all night." A 5 kWh battery delivers roughly 4 kWh usable. A 1.5-ton AC pulls 1.5 kWh/hr — so realistic AC runtime on a 5 kWh battery is 2–3 hours, not all night.
Hybrid + Battery vs DG Backup — Pros, Cons, Verdict
The straight choice for most outage-prone Indian households comes down to hybrid solar with a battery or on-grid solar plus a diesel generator. Below is the trade-off side by side.
- Pro Silent operation; zero local emissions
- Pro Instant cutover; no startup delay
- Pro Time-of-use arbitrage unlocks extra savings
- Pro 15-year LFP cell life under proper BMS
- Con ₹3–4 lakh capex premium
- Con Limited runtime — sized to nameplate
- Con Battery replacement cycle at year 10–15
- Pro Low capex — ₹55–80K all-in
- Pro Unlimited runtime — keep adding diesel
- Pro Familiar service ecosystem nationwide
- Pro No interaction with rooftop solar wiring
- Con Noise — 75–90 dB at one metre
- Con Diesel ₹15–25/kWh — punishes long outages
- Con Local air pollution; not future-proof
Verdict. If your monthly outage hours are above 5, the hybrid system pays back in 6–10 years and rewards you with silent, instant, clean backup. If your monthly outage hours are under 5 and your budget is tight, on-grid plus a 3–5 kVA DG is the rational compromise — accept the noise and fuel cost for the lower capex. Households in West Bengal, Bihar, eastern UP, and rural Odisha should default to hybrid. Households in Gujarat, Delhi NCR, and Bengaluru should default to on-grid with an optional small DG.
How Heaven Green Energy Designs Power-Cut Resilient Solar
Our residential design process starts with a 20-minute load and outage audit. We pull your last 12 months of electricity bills, ask for an honest count of outage hours per month, and map your essential loads (fans, lights, refrigerator, router, two ACs, water pump). From there we recommend one of the four configurations from the map above. We do not push hybrid systems on customers in Gujarat or Delhi NCR where the grid is stable; we do not sell pure on-grid systems to households in rural Bihar where outages exceed 25 hours a month.
When the call is hybrid, we standardise on LFP battery chemistry with a Tier-1 BMS (LiTime, Pylontech, BYD, or Luminous LFP), Deye or Sungrow hybrid inverters, and IS 16221-certified DC isolators. When the call is on-grid plus DG, we coordinate with a Honda or Kirloskar DG supplier and wire a manual or automatic transfer switch (ATS) that physically isolates the solar inverter from the DG output during a switchover. We do not ever attempt to parallel a non-synchronised DG with a grid-tied inverter — the risk to the inverter is unacceptable.
Explore the services that match your project:
- Residential Solar — on-grid, hybrid, and off-grid residential systems with PM Suryaghar subsidy handling.
- Solar Calculator — quick estimate of subsidy, payback, and battery sizing for your bill.
- Contact Heaven Green — speak to a designer about your specific configuration.
For a deeper read on system architecture choices, also see our guides on on-grid vs off-grid vs hybrid solar systems, lithium vs lead-acid for solar homes, the detailed 2026 battery chemistry breakdown, how to add a battery to existing solar, and solar vs inverter battery.
Frequently Asked Questions
Will my solar panels work during a power cut if I have an on-grid system?
No. A standard grid-tied (on-grid) solar inverter is mandated by IS 16221 Part 2 and IEEE 1547 to disconnect within 200 milliseconds when the grid voltage or frequency disappears. This anti-islanding feature is a safety measure to prevent backfeeding the utility line and electrocuting a lineman working on the fault. Even with sunlight pouring onto your panels, the inverter refuses to energise your house wiring until the grid is fully restored and stable for 5 minutes. Only hybrid systems with a battery can supply power during a cut.
What is anti-islanding and why does it matter?
Anti-islanding is a mandatory safety feature in every grid-tied solar inverter sold in India. It prevents an “island” — a section of the grid energised by a distributed generator while the rest of the line is dead — from forming during a power cut. Without anti-islanding, a lineman repairing a fault on the pole outside your home could touch a line they believe is dead and be electrocuted by your rooftop solar feeding it. The Bureau of Indian Standards codified the requirement in IS 16221 Part 2, mirroring the international IEEE 1547 standard.
How much does it cost to add a battery to my existing solar system for power cut backup?
Adding a battery to an existing grid-tied solar system requires two purchases: a hybrid inverter to replace your current grid-tied inverter (₹50,000–₹70,000 for a 5 kVA unit) and the battery itself (₹2.0–₹2.5 lakh for a 5 kWh LFP pack including the cabinet and BMS). The total retrofit cost is ₹2.5–₹3.2 lakh. Installation labour and wiring rework adds another ₹15,000–₹25,000. The existing solar panels and structure are reused; only the inverter changes.
Is a hybrid solar system worth it in 2026 for an Indian home?
It depends on your outage profile. If your area sees more than 5 outage hours per month — common in West Bengal, Bihar, rural Uttar Pradesh, and coastal Odisha — a hybrid system with a 5–7.5 kWh LFP battery pays back the resilience premium in 6–10 years through avoided diesel costs and time-of-use tariff arbitrage. In cities with stable grids like Ahmedabad, Bengaluru, and Delhi NCR, the hybrid premium is harder to justify and a pure on-grid system with an optional small diesel generator is more economical.
Can I run my air conditioner on a 5 kWh hybrid battery during a power cut?
Yes, but for a limited window. A 5 kWh LFP battery delivers around 4 kWh of usable energy after accounting for inverter losses and depth-of-discharge limits. A 1.5-ton split AC draws roughly 1.5 kWh per hour at steady state. Realistic AC runtime on a 5 kWh battery is therefore 2–3 hours. If you need to run an AC through a 6–8 hour evening outage, size the battery at 10–15 kWh and pair it with a 7.5–10 kVA hybrid inverter.
What is the difference between off-grid solar and hybrid solar?
Off-grid solar is fully independent of the utility — no grid connection at all. It requires an oversized battery bank (typically 30–50 kWh for an Indian 3-BHK) to survive multi-day periods of poor irradiance, plus a larger PV array to recharge that bank. Total cost runs ₹25–32 lakh. Hybrid solar keeps the grid connection but adds a smaller battery (5–10 kWh) for backup during outages, costing ₹6–10 lakh total. For any household with an existing DISCOM connection, hybrid is the financially correct choice.
Does PM Suryaghar subsidise the battery in a hybrid solar system?
No. The central PM Suryaghar subsidy of up to ₹78,000 covers only the grid-connected solar PV portion of the system. Batteries, hybrid inverters’ battery-management premium, and DG backup equipment are funded entirely by the homeowner. Some state schemes are exploring storage incentives, but as of mid-2026 no central scheme reimburses battery capex. Budget the battery separately when planning a hybrid system.
Why do most Indian homes still use a diesel generator as solar backup instead of a battery?
Capex and familiarity. A 5 kVA diesel generator costs ₹55,000–₹80,000 installed, versus ₹3–4 lakh for a hybrid system’s battery and inverter premium. For households with short, infrequent outages (5–10 hours per month), the DG’s higher running cost of ₹15–25 per kWh does not accumulate quickly enough to justify the battery’s higher capex. The DG also has unlimited runtime as long as diesel is available, while a battery is capped at its nameplate capacity. The trade-off flips toward batteries once outage hours exceed 15–20 per month.
