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₹32,990 buys a Sony 43-inch 4K TV this festive season, wearing a "45% off" badge against a ₹59,900 list price. Buy it at ₹30,240 or less, or wait. PriceHistory's September 2026 listing puts that set's recorded low at ₹28,800, which makes the badge a fake discount in the only sense your wallet cares about: it measures the saving from a price almost nobody paid, while the ₹4,190 gap to the low is what decides whether today is the day.

Why a fake discount survives every festive sale

It survives because the percentage is calculated from a list price the seller chooses, while the figure that decides value, the lowest price buyers recently paid, never appears on the product page at all.

A small badge is no safer. The same PriceHistory page shows an LG 9 kg front-load washer at ₹37,990, a modest 5% off, against a recorded low of ₹33,291: still about 14% above what it has sold for. The iPhone 16e at ₹69,900 carries a 54% premium over its ₹45,338 low. Buying a fridge too? Run this test before the 3-star vs 5-star refrigerator payback question.

The usual advice, compare against MRP, is out of date: MRP is a ceiling on the label, not a price the market sets. India's 2026 e-commerce amendment rules on prior prices push platforms toward showing real pre-sale prices. Until every listing does, a free tracker will.

Our rule, and it is a judgement rather than a citation: buy when the price sits within 5% of the recorded low. For the Sony that ceiling is ₹30,240, missed by ₹2,750. PriceHistory lists a 10% instant discount on SBI cards, which would bring the TV to ₹29,691 and pass, but only if the offer's cap is at least ₹3,299. The cap is not stated.

Four numbers decide how much checking falls on you, from Bar & Bench's 1 September 2026 review of CCPA dark-pattern orders, Storyboard18's June 2025 report on the self-audit advisory and PriceHistory's data from past Great Indian Festival sales.

The fines matter most. Bar & Bench counts seven platforms penalised, at ₹1 lakh to ₹7 lakh each: Zepto and FirstCry for drip pricing, BookMyShow for basket sneaking. For a national festive sale that is a rounding error, so the patterns persist and your own two-minute check is the protection that works.

So the test has to be portable, something you can run on a phone in the minute before you tap Buy.

How do I know if a discount is fake?

Compare the sale price with the item's lowest recorded price on a price history tracker, and treat it as genuine only when it falls within 5% of that low after every card offer and checkout fee is counted.

Read each row as a question to answer before paying.

Two rows carry the decision: the trigger gives a yes or no, and the card cap can turn a near miss into a real deal.

Where do I complain about dark patterns in India?

File with the National Consumer Helpline on 1915 or 1800-11-4000, by WhatsApp or SMS on 8800001915, or at consumerhelpline.gov.in, and attach screenshots, the URL, your cart or order ID, and the date and time.

But the product-page price is not your price until checkout agrees. A LocalCircles survey, reported by the Internet Freedom Foundation in October 2025, found drip pricing the most widespread dark pattern on Indian marketplaces; no sample size is given, so read it as a direction. Look at the final payable amount. Consumer Affairs Minister Pralhad Joshi has called extra cash-on-delivery charges a dark pattern and his department opened a probe, so a late COD fee is reportable.

A pay-later prompt at checkout can add interest to an overpayment; read how credit on UPI is changing what Indians spend before accepting one. Complaints also go through the Jagriti, UMANG or NCH apps, escalating to e-Jagriti.

One grey area remains. Trackers are third-party data with unstated methods, and a recorded low can be a flash price that lasted an hour, or less. Our view: it still beats a list price, but if the low looks like a glitch, use the next-lowest point.

• A countdown timer beside a price the tracker shows as routine.
• A fee, cash-on-delivery included, that appears only on the final screen.
• An item sitting in your cart that you never picked.
• A bank offer whose rupee cap is not shown before you pay.

The decision: this week, before the Diwali sales peak, put every item on your list into a free price tracker and write its 5% ceiling beside it. Buy what dips under it. Let the rest go, whatever the badge says.

₹8,499 buys the cheapest oil-filled radiator on Croma's room heater listing, the Orient Comforter 2,400 W. The Havells Bero 800 W quartz heater on the same page, checked on 8 October 2026, costs ₹1,749. Before you pick, know the one thing the oil heater vs fan heater argument usually skips: your electricity meter cannot tell them apart. Most Indian homes should buy a thermostat fan heater and keep the difference.

Which room heater uses less electricity, oil or fan?

Neither uses less electricity for the same heat, because every electric resistance heater converts all the power it draws into warmth, so an oil radiator and a fan heater of equal wattage cost exactly the same per hour. The US Department of Energy says so plainly on its Energy Saver page about electric resistance heating: such heating is 100% efficient at turning incoming electricity into heat (undated page, retrieved 8 October 2026). So any heater sold as energy saving is describing its thermostat, not its technology.

Oil radiators earn their thrifty reputation honestly, or half honestly, since the reason isn't the one the shop gives. Once the oil is hot, the thermostat clicks the element off and the fins keep shedding stored heat, so the meter rests. A fan heater with its own thermostat does the same thing. Strip that out and your bill comes down to watts, hours and the slab you are billed on. It is the logic behind the 3-star vs 5-star refrigerator payback by state tariff, except that here the efficiency gap is zero, so there is nothing to pay back. Room size, as with matching an air purifier's CADR to a room, changes how long a heater runs, not which type wins.

Delhi's DERC domestic slabs, as listed by Bridgeway Power in April 2026, charge ₹3.00 a unit for the first 200 units and ₹4.50 for the next 200, then rise. Take a fan heater like Morphy Richards' Aristo PTC, rated 2,000 W in Croma's own buying guide, and run it six hours a night for a month. A home already past the 400-unit line pays about ₹2,340 for that heat alone, before the PPAC surcharge. Four numbers decide whether the dearer heater ever earns back its price.

The hours figure is the one to sit with. Spend the radiator's premium on electricity instead and you could run a fan heater every winter evening through December and January and still have some left over. No running saving closes that gap, because none exists.

Oil heater vs fan heater: the seven rows that decide it

The fan heater wins on price and speed, while the oil radiator wins on burn risk and quiet, and those advantages matter mainly when a heater runs unattended through the night. Prices come from the opening's listing; hourly costs use the Delhi slab.

No row shows the radiator saving money. Its one solid win is safety, and it should be priced like a safety purchase. Delhi's bill side has its own sting, because the subsidy is a cliff, not a slope.

Is an oil filled radiator safe to leave on all night?

It is the safer of the two to leave running overnight, because it has no exposed glowing element to burn a child or pet, but only an ISI-marked unit with a working thermostat belongs in a bedroom. Croma's buying guide makes the burn point directly: exposed elements on fan and halogen heaters are unsafe for infants and pets. That argument holds only where someone small or frail sleeps.

The mark is not optional. Under a Bureau of Indian Standards quality control order, every electric room heater, liquid-filled radiators included, must carry the ISI mark (as of 2024, reported by The Tribune in February 2024). An unmarked listing is no bargain, and India's e-commerce rules on fake prior prices let you distrust a too-generous strike-through price.

My view on the grey area, and it is only a view: running any heater all night is the habit worth questioning, more than oil versus fan. Delhi bills also add a PPAC surcharge, reported so inconsistently this year that the only honest rate is the one on your bill. Before you pay, watch for:

• A listing that says energy saving without naming a thermostat.
• An oil radiator bought for short bursts before a bath.
• A fan heater with no tip-over cut-off in a room with toddlers.

So the decision is simple. Unless that card describes your bedroom, buy an ISI-marked PTC fan heater of the Aristo's rating with a thermostat and tip-over cut-off. This week, before the first cold night, pull out last winter's bill, note your monthly units, and add two units for every hour you plan to run the heater.

₹10,990 is the lowest price listed for the Xiaomi Smart Air Purifier 4 Lite, at Croma, according to MySmartPrice's tracker (retrieved 5 October 2026). Buy it for the bedroom. Skip it for an open hall, which needs a second unit or a bigger machine. The deciding number is the air purifier CADR, and most of us read it backwards: as a promise about our room, when it measures the machine.

How much CADR do I need for my room?

You need a CADR, in cubic feet per minute, of at least two-thirds of your room's floor area in square feet, so a 150 sq ft room wants about 100 cfm on a normal day. That is the rule published by AHAM, the Association of Home Appliance Manufacturers, which runs the CADR certification itself. It lets you size a purifier with a tape measure instead of trusting the carton.

Indian listings complicate it. Xiaomi quotes the 4 Lite's output in cubic metres per hour, while AHAM's rule works in cubic feet per minute, and one cfm equals 1.699 m³/h. So the 4 Lite's rated output converts to about 212 cfm. Run that through the normal rule and it suits rooms up to roughly 318 sq ft: a bedroom with ease, a typical living room just about. That conversion is this article's own arithmetic, not a figure Xiaomi prints.

AHAM is stricter for smoke. In a wildfire-grade week it wants smoke CADR to equal the full floor area, not a share of it, which pulls the 4 Lite's comfortable limit down to about 212 sq ft. The usual advice is to buy for the average day. That advice is wrong for North India. October to January is when the machine earns its price, so size it for those weeks.

Four numbers settle the purchase: Xiaomi's spec as MySmartPrice lists it, the GST share in the sticker, the coverage AHAM's smoke rule removes, and the wait since Bar & Bench reported in December 2025 that the Delhi High Court had asked the GST Council to meet "at the earliest" on purifier tax. The running-cost thinking behind our 3-star vs 5-star refrigerator payback by state tariff applies here, as does the festive urge to stretch a budget with credit on UPI and how it is changing Indian spending.

The smoke figure is the one to plan around. A living room the 4 Lite handles in October can fall short on the November mornings you will judge the purchase by.

So which rooms does one unit actually cover?

Air purifier CADR for a bedroom versus a hall

One Xiaomi 4 Lite covers a 120 sq ft bedroom in any week, with headroom to spare, but a 350 sq ft open hall needs two units or a single, much larger machine. Needs come from AHAM; margins are this article's arithmetic. Power assumes 33 W, ten hours a day for 120 days, about 40 units at ₹8 a unit; tariffs vary by state.

The bedroom clears every row; the hall fails both coverage rows, and a second unit helps only if its doorways can be closed.

Is GST on air purifiers 5% or 18% right now?

Assume 18%, the rate the Delhi High Court case was fought over, unless the GST Council's proposed cut to 5% has since been notified; we found reports of the proposal but no notification. PTI reported on 3 January 2026 that the Council was weighing that rate. At 5%, this price would fall by roughly ₹1,200, which sounds like a reason to wait. It isn't, or not yet.

Six days later the Centre told the court that classing purifiers as medical devices cannot decide the GST rate. My read, and it is opinion: any cut will come through a Council notification, and festive sales will not wait for it. If a Diwali listing claims a big markdown, check the 30-day prior price that India's e-commerce amendment rules on dark patterns and prior prices require.

The other traps are physical.

• AHAM's rule assumes 8 ft ceilings. At 10 ft a room holds a quarter more air, so treat the 4 Lite as roughly a 254 sq ft machine on a normal day.
• The filter, not electricity, is the recurring cost; we could not confirm its price, so check mi.com.
• Every figure assumes a closed room.
• A carton's "up to" coverage is not an AHAM figure.

So decide this week. If your bedroom passes all four checks, buy the 4 Lite at the lowest price you find; if it is the hall you want cleaned, price two units against one larger machine before the smog arrives.