The single most common question we get on a residential site visit in 2026 is simple — should I install a 3 kW, 5 kW, or 10 kW home solar system? All three sizes are popular because they cover the bulk of Indian homes: 3 kW is the subsidy sweet spot at ₹78,000 maximum central subsidy under PM Suryaghar, 5 kW is the standard mid-tier choice for households running two air-conditioners and an inverter fridge, and 10 kW is the residential net metering cap in most states — usually picked by villas, bungalows, and homes with EV (Electric Vehicle) charging or a pool pump.
Picking the wrong size costs you money in two directions. Go too small and you cap your subsidy claim and leave generation potential on the roof; go too large and the system exports surplus units that get credited at the APPC (Average Power Purchase Cost) — about ₹3.35/kWh — instead of saving the retail tariff at ₹7–₹8/kWh. This guide compares all three sizes head-to-head across cost, generation, payback, and roof footprint, and gives you a 4-input sizing matrix to land on the right number for your home.
Direct answer. For most Indian homes in 2026, a 3 kW system is the optimal size — it captures the full ₹78,000 PM Suryaghar subsidy, fits a sanctioned load of 3 kW, generates ~450 kWh/month, and pays back in 28–32 months. Pick a 5 kW if your bill exceeds ₹4,500/month or you run two ACs. Pick 10 kW only if your bill crosses ₹7,500/month, you have a villa-sized roof, and your sanctioned load supports it.
If your bill, roof, and budget all agree on a number, your sizing decision is settled in five minutes. Most of the friction comes from one of those three inputs pulling against the others — that is the case the matrix below is designed for.
How to Choose Home Solar Size — The Bill-to-kW Rule
Before opening any calculator, run the bill-to-kW thumb rule we use across Gujarat, Rajasthan, and Maharashtra installations: divide your average monthly electricity bill by ₹1,800. The result is the kW size that will offset roughly 90–95% of your consumption.
- ₹2,500 / 1,800 ≈ 1.4 → round up to 2 kW (you’ll qualify for ₹60,000 subsidy).
- ₹4,000 / 1,800 ≈ 2.2 → round up to 3 kW (hits the ₹78,000 subsidy ceiling).
- ₹6,500 / 1,800 ≈ 3.6 → round up to 4 kW or step to 5 kW for headroom.
- ₹12,000 / 1,800 ≈ 6.7 → round up to 7 kW or step to 10 kW if EV/pool is planned.
The thumb rule works because Indian residential tariffs cluster around ₹6.50–₹7.50/kWh in the upper slabs (where solar saves the most), and a kWp (kilowatt-peak) of solar generates roughly 1,400–1,650 kWh per year depending on city. That works out to ~₹22,000–₹28,000 in annual savings per kW installed, which back-solves to a monthly bill offset of ₹1,800/kW. For city-specific numbers, see our home solar system size guide.
The thumb rule has two boundary cases worth flagging. First, if you live in a state with a low retail tariff (Andhra Pradesh, Telangana domestic slabs sit closer to ₹4–₹5/kWh) the divisor shifts to ₹1,400/kW — your bill-implied size is slightly larger. Second, if you live in a state with a flat tariff structure that doesn’t escalate by slab (some union territories), the divisor moves to ₹2,000/kW because the marginal kWh you save is at the average tariff, not the upper slab. The ₹1,800 divisor is the right anchor for Gujarat, Rajasthan, Maharashtra, Karnataka, Tamil Nadu, and Delhi — which together represent the majority of PM Suryaghar applications.
The Home Solar Sizing Matrix — Bill, Roof, Budget, Sanctioned Load
This is the named framework we use on every Heaven Green site visit — The Home Solar Sizing Matrix. It pivots around four inputs, in this order: monthly bill, roof area, budget, sanctioned load. Whichever input is the most constrained sets your ceiling — there is no benefit to optimising for one and ignoring the others.
| Input | What it controls | 3 kW | 5 kW | 10 kW |
|---|---|---|---|---|
| Monthly bill (avg) | Right-sizes generation to consumption | ₹2,500–₹4,500 | ₹4,500–₹7,500 | ₹7,500–₹15,000 |
| Shadow-free roof area | Hard physical ceiling on panel count | ~300 sqft | ~500 sqft | ~1,000 sqft |
| All-in budget (post-subsidy) | Cash you actually deploy | ₹87K–₹1.07L | ₹1.82L–₹2.07L | ₹4.72L–₹5.72L |
| Sanctioned load on bill | DISCOM compliance ceiling | 3 kW min | 5 kW min | 10 kW min |
How to read the matrix. If your monthly bill says 5 kW but your roof can only host 3 kW of panels, you install 3 kW — there is no workaround. If the roof fits 10 kW but your sanctioned load is 3 kW, you either downsize to 3 kW or file for a load enhancement before applying (15–25 days, separate DISCOM workflow). Budget is the easiest constraint to relax because PM Suryaghar loans cover up to ₹2 lakh at 6.75% — explained in our PM Suryaghar complete guide.
Roof area is the constraint most homeowners underestimate. Modern N-type TOPCon panels at 580–620 Wp need ~100 sqft per kW including walkway and shadow buffers — older 540 Wp PERC panels needed 110–120 sqft per kW. South-facing slope or open terrace is non-negotiable for the full nameplate output.
Quick sanity check. Pull your last three electricity bills, average them, divide by ₹1,800 — that gives your “bill kW”. Then measure your shadow-free roof in sqft and divide by 100 — that gives your “roof kW”. The smaller of the two is your installable size. If both agree, you’ve got an easy install. If they disagree by more than 2 kW, book a site survey before ordering anything.
3 kW Home Solar — Best Fit, Cost, Generation, Subsidy
The 3 kW system is the subsidy sweet spot in India and the single most installed size under PM Suryaghar in 2025–26. It hits the ₹78,000 maximum central subsidy, fits the default 3 kW sanctioned load on most urban residential connections, and lands a payback inside 36 months in every major city.
Best fit. Monthly bill ₹2,500–₹4,500. Two- or three-bedroom home with 1 inverter AC, refrigerator, washing machine, ceiling fans, LED lighting, and one TV. Typical consumption profile: 400–500 kWh/month. Roof area available: 300+ sqft shadow-free.
Cost. ₹1.65–₹1.85 lakh all-in (panels, inverter, structure, AC/DC cabling, earthing, net meter coordination, GST). After ₹78,000 PM Suryaghar subsidy, out-of-pocket is ₹87,000–₹1,07,000.
Generation. ~450 kWh/month average across India, with a 5,400 kWh/year national average. Specifics vary by city — the table in §Generation, Savings, and Payback by City breaks this down.
Subsidy math. ₹30,000 for the first kW + ₹30,000 for the second kW + ₹18,000 for the third kW = ₹78,000. Going from 3 kW to 4 kW adds zero subsidy because the ₹78,000 cap kicks in at exactly 3 kW. This is why 3 kW is the densest rupee-of-subsidy-per-rupee-spent option.
Payback. 28–36 months across India — Jaipur and Ahmedabad on the lower end, Mumbai on the higher end. For a working example, see Suryaghar for a 3-AC home.
Loan affordability. Under PM Suryaghar’s collateral-free loan window, public sector banks finance up to ₹2 lakh at 6.75% for residential rooftop. For a 3 kW system, the post-subsidy ₹97,000 financed over 5 years works out to an EMI of ~₹1,900/month — almost exactly the bill saving you generate. From month one your net cash position is neutral, and from month 61 you’re saving ₹2,500–₹3,500/month for the remaining 20 years of panel life. That is why 3 kW is the most accessible PM Suryaghar size for first-time solar buyers: zero net outflow during the loan tenure, with full ownership of the asset.
5 kW Home Solar — Best Fit, Cost, Generation
The 5 kW system is the standard upgrade for homes that overshoot the 3 kW subsidy ceiling. The subsidy is still capped at ₹78,000, so the extra 2 kW costs you full retail — but the generation jump (~750 kWh/month) handles two ACs, an inverter fridge, and an electric water heater comfortably.
Best fit. Monthly bill ₹4,500–₹7,500. Three- or four-bedroom home with 2 inverter ACs running 6–8 hours/day, refrigerator, washing machine, geyser, induction cooktop, ceiling fans, LED lighting, and a small home office setup. Typical consumption: 650–800 kWh/month. Roof area required: 500+ sqft shadow-free.
Cost. ₹2.60–₹2.85 lakh all-in. After ₹78,000 PM Suryaghar subsidy, out-of-pocket is ₹1,82,000–₹2,07,000. Per-kW cost is lower than 3 kW because the inverter, structure, and BOS (Balance of System) costs scale sub-linearly.
Generation. ~750 kWh/month average. A well-orientated 5 kW system in Jaipur or Ahmedabad will produce closer to 800 kWh/month; the same system in Mumbai or coastal Karnataka produces closer to 580–620 kWh/month because of higher cloud cover and humidity.
Subsidy math. Still capped at ₹78,000 — the extra 2 kW above the 3 kW threshold is full-price. Effective per-kW cost: ₹36,400 (subsidised portion) for the first 3 kW, ₹52,000–₹56,000 for the next 2 kW. The payback math still works because the 2 extra kW carry the same per-rupee energy return — they just don’t carry subsidy.
Payback. 36–42 months across most cities. The extra capacity pays back slightly slower than the 3 kW sweet spot but still inside the standard 5-year horizon. For a deeper ROI build, see how to calculate solar ROI. A 5 kW system that runs from year four to year twenty-five at the same generation profile delivers cumulative savings north of ₹15 lakh in present-value terms — roughly 7x the post-subsidy investment.
Sizing your home accurately matters more than the brand of panels. Our 60-second solar calculator takes your bill, pin code, and roof type and outputs the right size with subsidy, savings, and payback. Talk to a Heaven Green advisor →
10 kW Home Solar — Best Fit, Cost, Generation, Net Metering Constraints
The 10 kW system is the residential ceiling. Most state DISCOMs cap residential NMM (Net Metering Mechanism) at exactly 10 kW — go above that and you fall into gross metering or net-billing regimes that pay APPC for all exported units, not just the surplus. This is why villas and bungalows that could physically host 15–20 kW deliberately stop at 10 kW.
Best fit. Monthly bill ₹7,500–₹15,000. Villa, bungalow, or large independent house with 3+ ACs running long hours, large refrigerator + deep freezer, dishwasher, geyser, induction cooktop, swimming pool pump, EV charger (3.3 kW or 7.2 kW), and a home theatre or workshop. Typical consumption: 1,200–1,600 kWh/month. Roof area required: 1,000+ sqft shadow-free.
Cost. ₹5.50–₹6.50 lakh all-in. After ₹78,000 PM Suryaghar subsidy, out-of-pocket is ₹4,72,000–₹5,72,000. The ₹78,000 subsidy is still capped at the 3 kW ceiling — it does not scale with system size for individual residential consumers.
Generation. ~1,500 kWh/month average. With Jaipur or Ahmedabad irradiance, expect 1,575–1,650 kWh/month. With Mumbai or Bengaluru irradiance, expect 1,170–1,250 kWh/month.
Net metering constraint. 10 kW is the residential cap in Gujarat, Rajasthan, Maharashtra, Karnataka, Tamil Nadu, and most other states under the MNRE Solar Rooftop Phase 2 framework. Going above forces gross metering — every unit your panels produce sells to the DISCOM at APPC (~₹3.35/kWh) and every unit you consume buys from the DISCOM at retail (₹7–₹8/kWh). The economics get worse by roughly 35%.
Sanctioned load constraint. 10 kW solar requires 10 kW sanctioned load on your bill. Most villas already have 7–10 kW sanctioned for the AC and pump loads — verify on your bill before applying. If you need to enhance, file the load enhancement with your DISCOM in parallel with the PM Suryaghar application.
Payback. 48–60 months. Longer than 3 kW or 5 kW because the per-kW subsidy cushion thins out, but still well inside the 25-year panel warranty. The bigger driver of 10 kW economics is consumption profile — homes that self-consume 70%+ of generation (EV charging, pool, daytime cooking) hit payback closer to 48 months; export-heavy profiles drift toward 60. For villa-specific sizing, see Suryaghar for a villa or bungalow.
Generation, Savings, and Payback by City
City-level numbers matter because PSH (Peak Sun Hours) varies meaningfully across India. The MNRE Solar Atlas pins Jaipur at 5.7–6.2 PSH/day, Ahmedabad at 5.5–5.9, Bengaluru at 5.0–5.4, Chennai at 5.1–5.5, and Mumbai at 4.6–5.1 — the cloudiest of the major metros.
Annual generation by city (kWh / year)
| City | PSH/day | 3 kW | 5 kW | 10 kW |
|---|---|---|---|---|
| Jaipur | 5.7–6.2 | 4,950 | 8,250 | 16,500 |
| Ahmedabad | 5.5–5.9 | 4,740 | 7,900 | 15,800 |
| Bengaluru | 5.0–5.4 | 4,500 | 7,500 | 15,000 |
| Chennai | 5.1–5.5 | 4,560 | 7,600 | 15,200 |
| Mumbai | 4.6–5.1 | 4,200 | 7,000 | 14,000 |
Assumptions: 75% performance ratio, modern TOPCon panels, south-facing, 10° tilt, annual degradation factored at 0.5%.
Cost breakdown — what you actually pay
| Line item | 3 kW | 5 kW | 10 kW |
|---|---|---|---|
| Panels (ALMM tier-1) | ₹78,000 | ₹1,30,000 | ₹2,60,000 |
| Inverter (BIS-certified) | ₹28,000 | ₹42,000 | ₹78,000 |
| Mounting structure | ₹18,000 | ₹30,000 | ₹60,000 |
| AC/DC cabling + BOS | ₹14,000 | ₹22,000 | ₹42,000 |
| Earthing + lightning arrestor | ₹8,000 | ₹10,000 | ₹14,000 |
| Net meter + DISCOM coordination | ₹6,000 | ₹6,000 | ₹8,000 |
| Installation + GST | ₹23,000 | ₹35,000 | ₹68,000 |
| All-in (pre-subsidy) | ₹1,75,000 | ₹2,75,000 | ₹5,30,000 |
| PM Suryaghar subsidy | (₹78,000) | (₹78,000) | (₹78,000) |
| Net out-of-pocket | ₹97,000 | ₹1,97,000 | ₹4,52,000 |
ALMM = Approved List of Models and Manufacturers (mandatory for subsidy eligibility under MNRE rules).
Match your monthly bill to system size
| Monthly bill (avg) | Recommended size | Why |
|---|---|---|
| ₹1,500–₹2,500 | 2 kW | Subsidy ₹60,000; payback 30–34 mo |
| ₹2,500–₹4,500 | 3 kW | Hits ₹78,000 subsidy cap; payback 28–32 mo |
| ₹4,500–₹7,500 | 5 kW | Two-AC homes; payback 36–42 mo |
| ₹7,500–₹10,500 | 7 kW | Subsidy capped; payback 42–48 mo |
| ₹10,500–₹15,000 | 10 kW | Villas/EV homes; payback 48–60 mo |
| Above ₹15,000 | 10 kW + storage | NMM cap; consider battery for self-consumption |
Payback by city and size (months, post-subsidy)
| City | 3 kW payback | 5 kW payback | 10 kW payback |
|---|---|---|---|
| Jaipur | 28 mo | 36 mo | 48 mo |
| Ahmedabad | 29 mo | 37 mo | 49 mo |
| Bengaluru | 31 mo | 39 mo | 53 mo |
| Chennai | 30 mo | 38 mo | 52 mo |
| Mumbai | 32 mo | 42 mo | 58 mo |
Assumptions: blended retail tariff of ₹7/kWh (state DISCOM tariff orders, 2024–25), 60% self-consumption, 40% net export at APPC ~₹3.35/kWh, system degradation 0.5%/year. For a city-specific recalculation against your actual bill, use the Heaven Green solar calculator or the methodology in our solar payback period guide.
Common Sizing Mistakes Buyers Make
We see the same six errors in roughly 70% of the pre-installation conversations we have. Each one is avoidable with a 10-minute check before signing the quotation.
-
1
Sizing on summer bills only. Summer AC load inflates the bill; winter consumption is half. Use the 12-month average, not May–June peaks. Oversizing by 30% is the most common error.
-
2
Picking 4 kW instead of 3 kW. The ₹78,000 subsidy ceiling sits at 3 kW. Choosing 4 kW costs the same per-kW as 3 kW but adds zero extra subsidy — you pay full retail for the fourth kW.
-
3
Ignoring sanctioned load on the bill. A 5 kW system on a 3 kW connection gets rejected at DISCOM feasibility. File the load enhancement first — 15–25 days — and submit Suryaghar after.
-
4
Skipping a shadow study. A water tank, parapet, or neighbouring building can cut output by 15–25%. Site survey before order, not after delivery.
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5
Going above 10 kW residential. You lose NMM eligibility in most states and fall into gross metering — exports pay APPC ~₹3.35/kWh instead of saving retail ~₹7/kWh. Roughly 35% worse economics.
-
6
Sizing for future EV without verifying timeline. If the EV is two years away, install for current load now and add an extension array later — extra capacity sitting idle erodes payback by 4–6 months.
Watch out
Vendors sometimes push a 4 kW or 5 kW quote on a 3 kW bill because the project margin is higher. Run the bill-to-kW thumb rule yourself before any conversation — if your bill divides to 3 kW, accept 3 kW. The subsidy economics will not improve at 4 kW.
3 vs 5 vs 10 kW — Side-by-Side Verdict
The pros and cons table below collapses the full comparison into a single view. Use it as the final sanity check before signing.
| Dimension | 3 kW | 5 kW | 10 kW |
|---|---|---|---|
| All-in cost (pre-subsidy) | ₹1.65–1.85 L | ₹2.60–2.85 L | ₹5.50–6.50 L |
| Net out-of-pocket | ₹87K–₹1.07L | ₹1.82–₹2.07L | ₹4.72–₹5.72L |
| Subsidy captured | ₹78,000 (full) | ₹78,000 (capped) | ₹78,000 (capped) |
| Generation/month | ~450 kWh | ~750 kWh | ~1,500 kWh |
| Roof needed | ~300 sqft | ~500 sqft | ~1,000 sqft |
| Sanctioned load | 3 kW | 5 kW | 10 kW |
| Bill range fit | ₹2,500–4,500 | ₹4,500–7,500 | ₹7,500–15,000 |
| Payback (avg) | 28–32 mo | 36–42 mo | 48–60 mo |
| NMM eligibility | Yes | Yes | Yes (cap) |
Pros and cons summary
- Pro Full ₹78K subsidy density
- Pro Lowest absolute payback
- Pro Default sanctioned load fits
- Con Caps generation at ~450 kWh
- Con Tight for 2-AC homes
- Pro Handles 2 ACs comfortably
- Pro Sub-linear BOS cost
- Pro 750 kWh/month buffer
- Con Subsidy stays at ₹78K
- Con Needs 5 kW sanctioned load
- Pro Full villa/EV/pool coverage
- Pro NMM cap — best of residential
- Pro 1,500 kWh/month generation
- Con Subsidy density lowest
- Con Payback drifts to 5 yrs
Verdict. Pick 3 kW unless something specific pushes you up — a bill consistently above ₹4,500/month, a confirmed second AC, or a villa-scale roof. The subsidy is densest at 3 kW, the payback is shortest, and the sanctioned load almost always matches by default. Step to 5 kW when consumption truly demands it. Step to 10 kW only when the bill, roof, and sanctioned load all unambiguously support it.
How Heaven Green Energy Sizes Home Solar
Heaven Green Energy is MNRE-empanelled and operates across Gujarat, Rajasthan, Maharashtra, Karnataka, and Tamil Nadu. We’re ranked #1 on the PM Suryaghar national portal by installation volume. Sizing every project follows the same 4-input matrix above, applied to your actual bill, roof, budget, and sanctioned load.
What you get when you book a site survey:
- 12-month bill analysis with seasonal correction (avoids summer-only sizing errors).
- Drone or measured-roof shadow study with hourly irradiance modelling.
- Three quotation tiers — 3 kW, 5 kW, 10 kW — with side-by-side payback so you can pick.
- ALMM-listed tier-1 panels (Adani, Waaree, Tata) and BIS-certified inverters as standard.
- End-to-end PM Suryaghar paperwork — portal submission, DISCOM feasibility, net meter inspection, DBT (Direct Benefit Transfer) tracking.
- 25-year performance support with O&M (Operations & Maintenance) contracts.
Explore the services that match your project:
- Residential Solar — 1–10 kW rooftop systems with full PM Suryaghar handling.
- Solar Calculator — see the right size for your bill in 60 seconds.
- Contact us — free site visit and quotation.
Why sizing accuracy matters more than brand selection. Across the residential installations we have completed in 2025, the single biggest predictor of customer satisfaction at the 12-month mark was sizing accuracy, not panel brand. A correctly sized 3 kW system on a ₹3,200/month bill outperforms an oversized 5 kW system on the same bill — because the 5 kW exports ~35% of its generation at APPC, eroding the payback math. We tier every quotation around the matrix output and never push a larger size unless the bill, roof, and sanctioned load all support it. If your bill grows in two or three years (a new EV, a second AC), we add a tied-in expansion array rather than oversizing upfront — it preserves the subsidy efficiency on the original system and keeps your cash deployment matched to your actual load curve.
Frequently Asked Questions
Is a 3 kW solar system enough for an average Indian home?
Yes — for a two- or three-bedroom home with one inverter AC, refrigerator, washing machine, ceiling fans, and LED lighting, a 3 kW system generates ~450 kWh/month which covers 90–95% of typical consumption. The ₹78,000 PM Suryaghar subsidy makes 3 kW the densest rupee-of-subsidy-per-rupee-spent option. Homes with two ACs running long hours should step up to 5 kW.
Why does the PM Suryaghar subsidy stop at ₹78,000?
The MNRE subsidy formula is ₹30,000/kW for the first 2 kW plus ₹18,000/kW for the third kW, summing to ₹78,000 at exactly 3 kW. Beyond 3 kW, no additional central subsidy applies for individual residential consumers. The intent is to spread limited subsidy budget across more households rather than concentrate it in larger installations.
Can I install 10 kW solar on a residential connection?
Yes, in most states. 10 kW is the residential net metering cap under the MNRE Solar Rooftop Phase 2 framework — Gujarat, Rajasthan, Maharashtra, Karnataka, and Tamil Nadu all permit 10 kW residential NMM. You’ll need 10 kW sanctioned load on your DISCOM bill, ~1,000 sqft of shadow-free roof, and ~₹4.72–₹5.72 lakh post-subsidy. Beyond 10 kW you fall into gross metering, which worsens economics by roughly 35%.
How much roof area do I need for 3 kW vs 5 kW vs 10 kW solar?
Modern N-type TOPCon panels (580–620 Wp) need roughly 100 sqft per kW of shadow-free roof, including walkway and edge buffers. That’s 300 sqft for 3 kW, 500 sqft for 5 kW, and 1,000 sqft for 10 kW. Tilted mounting structures used in regions with low summer sun (like the Konkan belt) may need 10–15% more. Always do a site survey before ordering — a parapet or water tank in the wrong place can reduce usable area by 20%.
Does the ₹78,000 subsidy apply to 5 kW and 10 kW systems too?
Yes — the ₹78,000 subsidy applies to any system of 3 kW or larger for individual residential consumers. The amount is capped at ₹78,000; it does not scale with system size beyond 3 kW. So a 5 kW or 10 kW system gets the same ₹78,000 subsidy as a 3 kW system. RWAs and group housing societies use a separate slab — ₹18,000/kW for common-area loads.
What’s the payback period for 3 kW vs 5 kW vs 10 kW home solar in 2026?
Post-subsidy payback runs 28–32 months for 3 kW, 36–42 months for 5 kW, and 48–60 months for 10 kW, depending on city. Jaipur and Ahmedabad sit at the lower end of every range because of higher peak sun hours; Mumbai sits at the higher end because of cloud cover. All three sizes pay back inside the 25-year panel warranty by a wide margin — the difference is whether you recover the cost in 2.5 years or 5 years.
Can I upgrade from 3 kW to 5 kW or 10 kW later?
Yes, but you cannot re-claim the PM Suryaghar subsidy on the additional kW — the subsidy is one-time per consumer. The extra capacity is added at full retail cost. You’ll also need to enhance your sanctioned load with the DISCOM and update the net metering agreement. Most homeowners who anticipate higher future consumption (EV, additional AC) install the larger size upfront — the marginal economics are better than retrofitting.
Does sanctioned load on my electricity bill limit my solar size?
Yes — your installed solar capacity cannot exceed the sanctioned load on your DISCOM bill without a load enhancement. A 3 kW sanctioned-load connection can install at most 3 kW solar. To go higher, file a load enhancement application with your DISCOM (15–25 days) before submitting Suryaghar. Heaven Green coordinates load enhancement and PM Suryaghar applications in parallel to minimise total delay.
