How Many Solar Panels Do You Need? Size Your System by Electricity Bill
Find out exactly what size solar system you need in UP based on your UPPCL electricity bill. Simple formula + real cost examples to avoid oversizing.
Most people who contact us about solar start with the same question: "Kitne kW ka system lagana chahiye?" And the honest answer is — it depends on how much electricity you actually use.
Not on what your neighbour installed. Not on what some random YouTube video recommended. Your electricity bill tells you almost everything you need to know.
This guide will walk you through the math, step by step. By the end, you'll know what size system fits your household — and you can head over to your city's pricing page for an exact cost quote.
Step 1: Find Your Monthly Unit Consumption
Your UPPCL electricity bill shows a number labelled "Units Consumed" or "kWh" — that's the number you need. If your bill shows a billing period that isn't exactly one month (sometimes it's 28 days, sometimes 35), adjust accordingly. But for most people, the printed number is close enough.
If you have your bill handy, look at it now. If not, here's a rough guide based on typical Indian household profiles:
Small household (2-3 people, fans, lights, one fridge, no AC): 100–200 units/month
Medium household (4-5 people, fans, lights, fridge, washing machine, TV, 1-2 ACs used 6-8 hours/day in summer): 250–500 units/month
Large household (5+ people, multiple ACs running long hours, geyser, submersible pump, double-door fridge): 600–1,200+ units/month
Don't have your bill? Check the UPPCL app or website — it shows your last 6 months of consumption history. You want the average, not the peak summer month and not the mild winter month. Take at least 4-6 months of bills across different seasons and average them out. Summer bills in UP are typically 40-60% higher than winter bills because of AC and cooler usage, so if you only look at your June bill, you'll oversize your system.
What You're Actually Paying Per Unit
Before we get to sizing, it helps to understand what you're paying. The Uttar Pradesh Electricity Regulatory Commission (UPERC) sets domestic tariffs under the LMV-1 rate schedule. For urban domestic consumers, the current telescopic slab structure looks like this:
| Monthly Consumption | Energy Charge per Unit |
|---|---|
| 0–150 units | ₹5.50 |
| 151–300 units | ₹6.00 |
| Above 300 units | ₹6.50 |
(Source: UPERC LMV-1 Urban Domestic schedule. Tariffs for FY 2026-27 were approved unchanged from the prior year via UPERC order in July 2026. Fixed charges of ₹110 per kW of sanctioned load per month apply separately. Rural domestic rates start lower at ₹3.35/unit for the first 100 units.)
On top of these energy charges, there's a 5% electricity duty and a small meter rent (~₹20/month). So a household consuming 400 units/month is effectively paying around ₹2,400–₹2,600 in energy charges alone, plus fixed charges.
The important thing to notice is that the more you consume, the more expensive each additional unit gets. This means solar saves you the most expensive units first — the ones at the top of the slab.
Step 2: Convert Units to System Size — The Simple Formula
Here's the rule of thumb that works reliably across Uttar Pradesh:
Monthly units consumed ÷ 120 = System size in kW
Where does 120 come from? According to data from the National Institute of Solar Energy (NISE) and the Global Solar Atlas, Uttar Pradesh receives a Global Horizontal Irradiation (GHI) of 4.8 to 5.4 kWh/m²/day, translating to roughly 4.5 to 5.2 peak sun hours per day across most districts.
In practice, after accounting for real-world system losses — inverter conversion efficiency (~96%), wiring and connector losses (~2%), soiling and dust accumulation (~3-5%), and panel temperature derating (~5-10% in UP's summer heat) — a 1 kW rooftop system generates approximately 4.0 to 5.0 kWh (units) per day. Over a month, that works out to about 120 to 150 units per kW installed.
(Source: NISE solar resource assessment data; Global Solar Atlas by World Bank/Solargis — globalsolaratlas.info. System loss factors based on MNRE performance ratio benchmarks of 78%–82% for rooftop systems.)
We use 120 as the divisor (not 135) because it builds in a conservative margin. Panels lose a little efficiency each year (typically 0.5–0.7% annually per manufacturer datasheets), dust accumulates between cleanings, and some months are cloudier than average. It's better to have a system that covers your consumption comfortably than one that falls just short.
⚡ Quick reference:
150 units/month → ~1.25 kW (round up to 2 kW)
300 units/month → 2.5 kW (round up to 3 kW)
500 units/month → ~4.2 kW (go with 5 kW)
750 units/month → ~6.25 kW (go with 7 kW)
1,000 units/month → ~8.3 kW (go with 8 kW or 10 kW)
You'll notice we round up to standard system sizes. That's because inverters and panel arrays come in fixed configurations — you can't install a 4.2 kW system. The standard residential sizes available are 1 kW, 2 kW, 3 kW, 4 kW, 5 kW, 6 kW, 8 kW, and 10 kW.
Worked Examples with Real UP Household Numbers
Note: Unit (kWh) consumption — not the rupee amount on your bill — is the primary sizing input. The ₹ figures in the examples below are illustrative only to help you relate to the cost, and are not a sizing method in themselves.
Example 1: A family in Varanasi with a ₹2,200 monthly bill
A typical Varanasi household paying around ₹2,200/month in energy charges is consuming roughly 250–300 units. At the UPERC urban domestic rate, 300 units would cost: first 150 units × ₹5.50 = ₹825, next 150 units × ₹6.00 = ₹900, totalling ₹1,725 in energy charges — plus ₹110 fixed charge per kW of sanctioned load, electricity duty, and meter rent, bringing the total bill to roughly ₹2,000–₹2,300.
Using our formula: 280 units ÷ 120 = ~2.3 kW
Recommendation: A 3 kW on-grid system covers this comfortably. Based on NISE generation benchmarks, it'll generate around 360–405 units/month on average across the year — enough to bring the variable energy charges down to near-zero through net metering.
The 3 kW size also hits the sweet spot for subsidy: it qualifies for the full ₹78,000 central subsidy from MNRE plus ₹30,000 UPNEDA state top-up (more on subsidies below).
→ Check 3kW system price in Varanasi
Example 2: A joint family in Lucknow with a ₹4,000 monthly bill
A Lucknow family paying ₹4,000/month in energy charges is likely consuming around 500–550 units. At the UPERC urban rates, 500 units would cost: 150 × ₹5.50 + 150 × ₹6.00 + 200 × ₹6.50 = ₹825 + ₹900 + ₹1,300 = ₹3,025 in energy charges. With fixed charges and duty, the total reaches ₹3,500–₹4,000.
Using our formula: 520 units ÷ 120 = ~4.3 kW
Recommendation: A 5 kW on-grid system is the right fit. It generates roughly 500–675 units/month depending on the season. If consumption spikes in peak summer, the shortfall gets drawn from the grid as usual — and the surplus generated in winter and spring gets banked as net metering credits.
→ Check 5kW system price in Lucknow
Example 3: A large bungalow in Noida with an ₹8,000+ monthly bill
This household is consuming around 1,000–1,100 units/month across multiple ACs, geysers, and a submersible pump. At the UPERC rate, 1,000 units would cost: 150 × ₹5.50 + 150 × ₹6.00 + 700 × ₹6.50 = ₹825 + ₹900 + ₹4,550 = ₹6,275 in energy charges, reaching ₹7,200–₹8,200 with fixed charges and duty.
Using our formula: 1,050 units ÷ 120 = ~8.75 kW
Recommendation: A 10 kW on-grid system is the best fit. Under UP rules, rooftop systems up to 10 kW are exempt from requiring a No-Objection Certificate (NOC) from the State Electrical Inspector (Source: UPNEDA FAQ), making it a practical threshold. Separately, remember that your actual system size is capped by your sanctioned/contracted electrical load, not by a fixed net-metering ceiling. Based on NISE generation data for the Noida/NCR region, this system will generate roughly 1,200–1,500 units/month in good months — generation should be checked against the household's full annual consumption, not just peak months.
→ Check 10kW system price in Noida
Step 3: Check if Your Roof Can Handle It
The formula gave you a number, but your roof has to agree. Here's what matters:
Shadow-free area needed per kW: roughly 80 to 100 sq ft (about 7.5 to 9.3 sq metres). This assumes modern mono-PERC or TOPCon panels in the 540–580 Wp range. Each panel measures approximately 2.27 m × 1.13 m (~27.6 sq ft), but you need to add space for inter-row tilt spacing (to prevent row-to-row winter shading at 24°–26° tilt angle), maintenance walkways (500–600 mm minimum), and clearance from parapets, water tanks, and staircase rooms.
(Source: Standard industry sizing norms based on BIS mounting standards and MNRE technical specifications for rooftop solar.)
| System Size | Approx. Number of 550W Panels (DC array capacity) | Shadow-Free Roof Area Needed |
|---|---|---|
| 1 kW | 2 panels | 80–100 sq ft |
| 2 kW | 4 panels | 160–200 sq ft |
| 3 kW | 6 panels | 240–300 sq ft |
| 5 kW | 9–10 panels | 400–500 sq ft |
| 10 kW | 18–20 panels | 800–1,000 sq ft |
The key word here is shadow-free. If your roof has a water tank, staircase headroom (mumty), dish antenna, or a taller neighbouring building casting shadows for part of the day, that area doesn't count. Shadows don't just reduce output from one panel — in a string inverter setup (which most residential systems use), a shadow on even one panel drags down the whole string.
If your roof is smaller than what your electricity consumption demands, you have two choices: install the maximum your roof allows and reduce your bill partially, or switch to higher-wattage panels (like 580W bifacial modules) that squeeze more capacity into less space. Our site survey will assess this and recommend the right layout.
Roof type matters too. RCC (pucca concrete) roofs are ideal — panels mount directly on a raised mounting structure. Tin or sheet roofs need special clamp-based mounting. Sloped tile roofs work but cost a bit more to install. Ground-mounted systems are possible but less common in residential settings and not always eligible for the residential net metering category.
How Sunlight Hours in UP Affect Your System
According to the Global Solar Atlas (World Bank/Solargis), Uttar Pradesh receives a Global Horizontal Irradiation (GHI) of 4.8 to 5.4 kWh/m² per day, which corresponds to approximately 4.5 to 5.2 peak sun hours per day across most districts. This is a decent solar resource — not as high as Rajasthan (5.5–6.5 kWh/m²/day GHI), but significantly better than most of Europe or the northeast Indian states.
(Source: Global Solar Atlas — globalsolaratlas.info; NISE Solar Radiation Resource Assessment)
The generation varies by season. Based on NISE monitoring data for the Indo-Gangetic plain:
- Pre-monsoon and summer (March–June): Peak output — roughly 4.8 to 5.5 units per kW per day. Long days and high irradiance.
- Monsoon (July–September): Moderate output — roughly 3.2 to 4.0 units per kW per day. Cloud cover and rain reduce generation, but panels still produce on overcast days (they respond to diffuse light too).
- Winter (November–January): Lower output — roughly 2.8 to 3.8 units per kW per day. The Indo-Gangetic plain's dense winter fog and smog reduce irradiance noticeably, and the lower sun angle shortens effective generation hours. By February, output recovers to 4.2–4.8 units/kW/day.
The annual average is what matters for system sizing, because UPPCL net metering works on a billing-cycle basis — surplus units generated in sunny months get credited against shortfall in cloudy months. So you don't need to size for the worst month. You size for the annual average.
This holds true across UP — whether you're in Agra, Gorakhpur, Meerut, Jaunpur, or Prayagraj. The solar irradiance variation within the state is roughly 10-15%, which is well within the safety margin our formula already builds in.
What About Household Appliance Load?
Some people approach sizing from the other direction: adding up every appliance wattage and calculating total load. That method works in theory, but it's unnecessarily complicated for most homes. Here's why.
An on-grid solar system doesn't need to power all your appliances simultaneously. It feeds electricity into the grid through your meter, and your appliances draw from the same grid. So the question isn't "can my system power 3 ACs at once?" — the question is "does my system generate enough total units over the month to offset what I consume?"
That said, appliance awareness helps in two situations. First, if you're about to add a major load — like installing a new AC, a water heater, or an EV charger — you should account for that expected increase when sizing your system. A 1.5-ton split AC running 8 hours a day adds roughly 250-290 units/month to your bill (based on a typical 3-star or efficient inverter unit drawing 1.0–1.2 kW). Note that this varies depending on the AC's ISEER rating and room size. Second, if you're going off-grid or hybrid (with battery backup), then instantaneous load matters because the inverter and batteries must handle the peak draw.
For on-grid systems (which are what most residential customers install because they qualify for subsidy and net metering), stick with the bill-based formula. It's simpler, more accurate, and doesn't require you to count every tube light.
Common Sizing Mistakes to Avoid
Mistake 1: Sizing for summer peak only
Your June bill might show 800 units because the ACs ran nonstop. But your December bill might be 250 units. If you install an 8 kW system to cover the peak, you'll be generating way more than you need for 8 months of the year. On-grid net metering does carry forward credits, so excess isn't "wasted" exactly — but surplus units beyond your annual consumption are settled at the much lower Average Power Purchase Cost (APPC) rate, not the retail rate you pay. According to UPERC net metering regulations, this settlement rate is significantly lower than the ₹5.50–₹6.50/unit you save by self-consuming. So massive oversizing means you're investing capital for electricity you sell back cheaply. Size for the annual average instead.
Mistake 2: Undersizing to save money
A 2 kW system is cheaper than a 3 kW system, obviously. But if your actual consumption needs 3 kW, the 2 kW system will only offset part of your bill, and you'll keep paying the rest to the DISCOM — at rates that increase regularly with UPERC tariff revisions. The per-kW cost of solar is actually lower at larger sizes (a 5 kW system costs less per kW than a 2 kW system), so there's a natural economy of scale working in your favour. Don't undersize just to keep the upfront number low.
Mistake 3: Ignoring future consumption growth
If you're building a new floor, planning to add ACs, or expecting your family to grow, size for where your consumption will be in 2-3 years — not where it is today. Adding capacity later is possible but more expensive than getting it right the first time (you may need a new inverter, additional wiring, and a fresh net metering application with the DISCOM).
Mistake 4: Copying your neighbour's system size
Your neighbour's 3 kW system works great for their family of three. But your family has two ACs and a submersible pump. Copying their system size without checking your own bill will leave you disappointed. Always start from your own consumption data.
Mistake 5: Confusing panel wattage with system size
"I want 6 panels" isn't a useful specification. Six 330W panels give you ~2 kW. Six 545W panels give you ~3.3 kW. The system size (in kW) is what determines how much electricity you generate — not the number of panels. Always think in terms of kW, not panel count.
How Subsidies Affect Your Sizing Decision
Under PM Surya Ghar Muft Bijli Yojana, residential homeowners in UP receive a two-part subsidy:
Central Financial Assistance (CFA) from MNRE:
- ₹30,000 per kW for the first 2 kW = ₹60,000
- ₹18,000 per kW for the next 1 kW (2 to 3 kW) = ₹18,000
- Total central CFA for a 3 kW system: ₹78,000 (capped; no additional CFA above 3 kW)
State Top-up Subsidy from UPNEDA (UP Solar Energy Policy 2022):
- ₹15,000 per kW, capped at ₹30,000 maximum
Combined total subsidy for a 3 kW system in UP: ₹1,08,000
For systems above 3 kW (say 5 kW or 10 kW), the subsidy remains flat at ₹1,08,000 — it doesn't increase further.
(Source: MNRE PM Surya Ghar Operational Guidelines — pmsuryaghar.gov.in; UPNEDA state subsidy notification under UP Solar Energy Policy 2022 — upneda.org.in)
What this means for sizing: there's a strong financial incentive to install at least 3 kW if your consumption supports it. At 2 kW, you get ₹60,000 (central) + ₹30,000 (state) = ₹90,000. Going to 3 kW unlocks another ₹18,000 in central subsidy — bringing the total to ₹1,08,000. But going from 3 kW to 5 kW adds no extra subsidy, so you're paying the full incremental cost yourself. That's still worthwhile if your consumption justifies it, since the electricity savings are real. But it changes the payback math.
For the complete subsidy breakdown, eligibility criteria, required documents, and step-by-step application process, see our detailed PM Surya Ghar subsidy guide.
Eligibility requirements (per MNRE guidelines): You must have a residential (domestic) electricity connection with UPPCL, own the property, have a structurally suitable roof, and install solar panels through an empanelled vendor. Note that for the PM Surya Ghar subsidy, panels must meet two distinct requirements: they must be ALMM-listed (the approved models list), and they must strictly comply with DCR (Domestic Content Requirement), meaning both cells and modules are manufactured in India. Be aware that MNRE tightened ALMM List-II cell certification requirements in June 2026. Always explicitly confirm both DCR and ALMM compliance with your installer before proceeding. The subsidy is disbursed directly to your bank account via DBT after net meter commissioning and DISCOM inspection.
FAQ
That depends on the wattage of the panels you choose. With 545–550W mono-PERC panels (which are the most commonly installed in India right now), you need 5–6 panels for a 3 kW system. With older 330W panels, you'd need 9–10. The panel count is less important than the total system capacity in kW — that's what determines your monthly generation.
You can, but there's usually no financial reason to. Under UPERC net metering regulations, surplus units beyond your annual consumption are settled at the Average Power Purchase Cost (APPC) rate — which is significantly lower than the ₹5.50–₹6.50/unit retail rate you pay. So oversizing means you're generating electricity that you sell back at a fraction of what you'd pay for it. Size your system to match your consumption, not exceed it significantly.
(Source: UPERC (Rooftop Solar PV Grid Interactive Systems Gross/Net Metering) Regulations)
Neither — use the annual average. Take your last 12 months of bills (or at least 4-6 months covering different seasons), add up the total units, and divide by the number of months. This gives you the most accurate baseline. Net metering carries credits forward, so surplus generation in sunny months offsets shortfall in cloudy or low-consumption months.
The sizing formula above works the same for your panel array, regardless of whether you add batteries. Batteries are sized separately based on how many hours of backup you want and what load you need to run during a power cut. For example, if you want to run 2 fans, a few lights, a fridge, and a WiFi router (roughly 500W) for 4 hours of backup, you'd need about a 2.5 kWh battery bank. Your Ensolvar site surveyor will help you calculate this if you opt for a hybrid system.
Yes. South-facing roofs get the most sunlight in India and are ideal — panels are mounted at a fixed tilt of 24°–26° (matching UP's latitude range of 25°N–29°N) facing true south. East or west-facing roofs work too but generate about 10-15% less over the year. North-facing roofs are the worst for solar and are generally avoided. If your roof faces east-west, you might need a slightly larger system to compensate for the reduced output per panel.
(Source: MNRE technical guidelines for rooftop solar orientation)
A correctly sized on-grid system can eliminate most of the variable energy charge on your bill, though fixed charges (₹110 per kW of sanctioned load per month for urban domestic), electricity duty (5%), and meter rent (~₹20/month) remain.
The PM Surya Ghar subsidy application requires property ownership documents, and the installation involves fixing panels permanently to the roof. If you rent, you'd need your landlord's written consent and cooperation. The subsidy and net metering benefits are tied to the electricity consumer account, which would need to be in the applicant's name. Practically speaking, this arrangement is uncommon — solar is primarily a homeowner investment.
Ready to Find Out Exactly What You Need?
You now have a solid idea of what kW system matches your household. The next step is a free site survey — we'll check your roof, confirm the layout, verify shade conditions, and give you an exact quote with brand options (Tata, Adani, Waaree, and other ALMM-listed panels).
Get in touch on WhatsApp or call us directly. There's no charge for the consultation and no obligation.
Once you know your system size, check the exact pricing for your city:
Or browse all service locations to find your district.
Data Sources Referenced in This Article
| Data Point | Source |
|---|---|
| Solar irradiance & peak sun hours in UP | Global Solar Atlas (World Bank/Solargis) — globalsolaratlas.info; NISE Solar Radiation Resource Assessment — nise.res.in |
| Generation per kW (4.0–5.0 kWh/day) | MNRE performance ratio benchmarks (78–82% PR); NISE monitoring data for Indo-Gangetic plain |
| System loss factors | MNRE Technical Specifications for Grid-Connected Rooftop Solar PV Systems |
| UPPCL domestic tariff slabs (LMV-1) | UPERC Tariff Order (FY 2026-27) — uperc.org |
| PM Surya Ghar subsidy slabs | MNRE Operational Guidelines — pmsuryaghar.gov.in |
| UPNEDA state top-up subsidy | UPNEDA notification under UP Solar Energy Policy 2022 — upneda.org.in |
| Net metering surplus settlement | UPERC (Rooftop Solar PV Grid Interactive Systems Gross/Net Metering) Regulations |
| Roof area per kW | BIS mounting standards; MNRE technical specifications for rooftop solar |
| Panel tilt angle (24°–26°) | MNRE guidelines; latitude-based optimization for 25°N–29°N |
| AC consumption estimate (1.5T, BEE 3-star) | BEE (Bureau of Energy Efficiency) star label energy consumption data |
| Panel degradation rate (0.5–0.7%/year) | Manufacturer datasheets (IEC 61215 / IEC 61730 certified modules) |
