Punjab's Smog Season vs Your Solar Panels: Why Winter Output Drops 40–60% and How to Size Around It

• By Best Solar Company PK
• 23 Jul, 2026
• Solar Guides
• 7 min read

Every October, a grey lid settles over central Punjab. From roughly mid-October to late January, Lahore, Multan, Faisalabad and Gujranwala sit under a mix of crop-burning smog, industrial haze and dense river-valley fog. It looks unhealthy — and it is — but if you own solar panels, it also quietly eats your electricity generation for three to four months. Many homeowners who sailed through summer with a zero bill are shocked when the January bill lands at Rs 15,000 or more.

The good news: this is predictable, and you can design around it. Let's look at exactly how much output you lose, why it matters far more under the new 2026 rules, and how to size your system so winter bills still stay near zero.

How much output you actually lose

Across Pakistan, December and January generation runs roughly **40–60% below** the July–August peak. Only about 35% of a system's annual output is produced between the September and March equinoxes; the other 65% comes in the sunnier half of the year.

In smog-hit Punjab the winter dip is at the harsher end of that range, for four stacked reasons:

• **Shorter days and a low sun angle** — the sun sits low in the southern sky, so light travels through more atmosphere and strikes a flat panel at a poor angle.
• **Smog and haze** scatter and absorb sunlight even when it isn't fully overcast, shaving irradiance on "sunny" days.
• **Dense fog** in December–January can black out the first several hours of daylight entirely; on a bad fog morning in Lahore, a system may produce almost nothing until 11am.
• **Soiling** — smog deposits a sticky film of soot and dust on the glass. Uncleaned panels in a smoggy city can lose an extra 15–25% on top of everything else.

In real numbers: a well-installed 10 kW system in Lahore might push **50–55 units a day in June** but only **18–25 units a day** through the worst of Dec–Jan smog. That is the gap you have to plan for.

Why 2026 changed the maths completely

This used to matter less. Under the old net-metering regime, you could "bank" surplus summer units against the grid at a 1:1 value and draw them back in winter, so an annual match was enough.

That era is over. Under **NEPRA's Prosumer (Net-Billing) Regulations notified on 9 February 2026**, new solar consumers no longer get 1:1 banking. Instead:

• Electricity you **export** is bought at a low buyback rate — around **Rs 8–11 per unit** for new prosumers (existing net-metering consumers were grandfathered at the older Rs 25.32).
• Electricity you **import** from the grid is billed at your full slab rate — commonly **Rs 37–55 per unit before taxes**, and higher once GST and fuel adjustments are added.
• The system-size cap dropped from **150% to 100% of your sanctioned load**.

The takeaway is blunt: **a winter unit you import can cost 4–6 times what a summer unit you export earns you.** Oversizing to dump cheap surplus onto the grid in summer no longer pays. The winning strategy now is to generate — and use — as much of your own power as possible, precisely when smog is trying to stop you. See our net-billing explainer for the full rule change.

Sizing so winter bills stay near zero

Here is a practical, five-step approach we use for Punjab customers.

**1. Size to your winter day, not your summer day.** Add up the units you actually consume during daylight in December — geyser, washing, pumps, daytime fans and lights. Divide by a conservative winter yield of about **2.5–3 units per kW per day** (versus 5+ in summer). A home needing 20 daytime units in January therefore needs roughly **7–8 kW**, not the 4–5 kW a summer-only calculation would suggest.

**2. Push toward your 100% load cap.** Since you can no longer install 150%, install as close to your full sanctioned load as the rules allow. Every extra panel is winter insurance, and surplus summer generation still earns something rather than nothing.

**3. Add storage for the fog window.** A 5–10 kWh lithium (LFP) battery lets you capture your limited midday winter generation and use it that same evening instead of importing at Rs 50+. In a net-billing world, self-consumption beats export, so batteries pay back faster than they did under old net metering. Our home battery guide walks through sizing.

**4. Shift heavy loads to the midday window.** Run the washing machine, iron, water pump and dishwasher between about 11am and 3pm, when even a foggy day gives you your best output. This one behavioural change can cut winter import dramatically at zero cost.

**5. Fight soiling and the sun angle.** Clean your panels every 2–3 weeks through smog season — recovering 15–20% of lost output for the price of a bucket of water is the cheapest "upgrade" you will ever make. If you have adjustable mounts, steepening the tilt for winter (closer to **45°** in Lahore, versus a ~30° annual setting) captures more of the low winter sun.

A worked example

Take a Multan household with a 400 sq. yd. home, a 12 kW sanctioned load and Rs 28,000 summer-zero bills already achieved on an 8 kW system. In smog season their output halves and the January bill creeps back to Rs 12,000. Upgrading toward the 12 kW cap (about **7 extra 585W bifacial panels at ~Rs 26,000 each**, roughly Rs 180,000 in panels plus balance-of-system) plus load-shifting typically brings that January bill back under Rs 2,000–3,000 — a payback measured in a couple of winters, not decades.

Frequently Asked Questions

**Does smog really reduce solar output, or just fog?** Both do, through different mechanisms. Fog physically blocks the sun for hours at a stretch, while smog haze scatters and dims light all day and coats your panels with soot. Together they are why Punjab's winter dip is worse than a clean-air city at the same latitude.

**How many extra panels do I need for winter?** As a rule of thumb, size around **25–35% more capacity** than a summer-only calculation suggests, and get as close to your 100% sanctioned-load cap as the net-billing rules permit. The exact number depends on your December daytime usage.

**Is it still worth going solar after the 2026 net-billing change?** Yes — but the payback now comes from **avoiding expensive grid imports**, not from selling surplus. With import slabs at Rs 37–55+ per unit, every unit you generate and use yourself is worth far more than the Rs 8–11 export rate. Self-consumption and storage are where the savings live.

**Should I add a battery just for smog season?** If your winter bills spike badly, yes. A modest LFP battery captures scarce midday winter output for evening use and shields you from the highest import slabs. Under net billing, storing your own power beats exporting it cheaply.

**When should I clean my panels in winter?** Every two to three weeks during October–January, and after any light rain that leaves muddy residue. Smog soiling is one of the biggest — and cheapest to fix — sources of winter loss.

Plan for the fog, and Punjab's fifth season stops being a nasty billing surprise. Talk to our team about a winter-first system sizing for your Lahore or Multan home.

**Sources:** NEPRA net-billing regulations 2026 (Profit), NEPRA new metering rules (Mettis Global), Summer vs winter generation (MaxGreen Energy), 585W bifacial panel prices (Pakistan Solar Traders), 2026 tariff slabs (Bill.com.pk / LESCO), Lahore smog "fifth season" (Frontiers)

Best Solar Company PK designs and installs reliable solar systems in Rawalpindi, Islamabad, Lahore, Multan, Taunsa Sharif and Karachi. Contact us for a free survey and the best advice for your home or business.