BenQ W4100i: problems, parts and running costs

Checked: 2026-10-21

Summary

The W4100i is a 4K home theater projector whose recurring complaints are practical rather than fatal: the third HDMI input accepts 4K/120 but renders it at 1080p/120, single-chip DLP throws rainbows onto bright highlights and small text, black level is grey next to dedicated cinema displays, and the fan is audible at 39–41 dBA measured about 3 feet away. Electricity is the only real running cost, roughly $73 a year for three hours a day at an assumed $0.20 per kWh, and there is no lamp to buy. It is worth $2,200 to $2,500, with $2,379 at B&H the best price seen in October 2026, and weak value above about $2,800.

Common problems and fixes

The third HDMI input is not really 4K/120 — HDMI3 takes a 4K/120 signal and renders the picture at 1080p/120, so a 4K/120 console is not the experience the port label suggests; HDMI1 and HDMI2 carry 4K/60 with ALLM and HDMI2 adds eARC. Fast mode is available but drops keystone correction and some processing. [1][2][8]
Rainbow artifacts on bright highlights and small text — ProjectorCentral and What Hi-Fi? both caught red, green and blue flashes on this model, and owners on r/projectors report the same picture on their own units. The effect comes with single-chip DLP and picture presets do not remove it, so look at real content in person if you are sensitive. [8][9][14]
Black level is grey — a calibrated BenQ-supplied unit measured about 1,046:1 on/off contrast in Cinema Normal, far below the 3,000,000:1 figure on the box, which is a dynamic number rather than on/off contrast. [8][11][9]
Fan noise in quiet scenes — BenQ rates 30dB in Normal, but ProjectorCentral measured 39–41 dBA at about 3 feet in Normal and 34–36 dBA in ECO. [2][8]
Color shift in the Dynamic source modes — ProjectorCentral saw red and green shift in Low/High Dynamic on some 4K scenes, and Normal avoided it there; What Hi-Fi? advised a lower Dynamic setting, which weakens HDR punch. [8][9][11]
Default HDR noise reduction smears motion — What Hi-Fi? found the default setting causes smearing and lag in dark, motion-heavy scenes and recommended turning it off. [9]
Clicking during picture-mode changes — an owner thread raises the clicks, and other owners read the sound as an iris or mode-switching noise rather than a fault; without a service diagnosis it is neither a confirmed fault nor a confirmed normal behavior. [16]
Light spill beyond the image — one owner posted a photo of spill on a 150-inch screen while showing a 120-inch image, with lens shift appearing to move the spill; the post does not establish whether the cause is screen mismatch, stray internal light or the mount. [15]

Parts and consumables

QS02 Android TV dongle — $149 in the BenQ US accessory catalog in October 2026; it runs Android 11 rather than Google TV, and some owners find it slow, so a separate streaming box is the alternative. [3][6]
CMG3 universal ceiling mount — $79 in the BenQ US projector shop in October 2026; the W4100i specification lists CM00G3 as the compatible mount, so confirm thread pattern and weight rating with BenQ before ordering. [2][3]
Air and dust filters — no OEM consumer filter cartridge, part number or US cost for the W4100i was found; the manual’s maintenance section covers exterior and lens cleaning and authorized repair only. [1]

Yearly running cost

BenQ lists 330W typical at 110V and under 0.5W in standby. Three hours a day for 365 days works out to 1,095 hours and 361.35kWh, about $72.27 a year at an assumed $0.20 per kWh, with standby adding at most 3.83kWh, roughly $0.77, so about $73 a year in total under those assumptions. Two hours a day at the same rate gives 240.9kWh and about $48.18 a year. There is no lamp and no paid streaming tier to buy; the LED block is rated 20,000 hours in Normal and 30,000 in ECO, which at three hours a day is about 18.3 years of run time on paper, not a promise that brightness, fans or electronics stay undiminished that long. [1][2][8]

When it is a good buy

Store snapshots from October 2026 put the W4100i at $2,499 on BenQ’s own shop, a $500 cut from the $2,999 launch price, at $2,379 on promotion at B&H and at $2,799.99 at Best Buy. Those captures disagree with each other, so check the cart at the store you plan to use. Below about $2,199 is strong value, $2,200 to $2,399 is attractive if B&H’s $2,379 promotion is live, $2,400 to $2,599 is reasonable at BenQ’s $2,499, and $2,800 to $2,999 is weak value while lower prices sit at other authorized retailers. [3][12][13]

Three alternatives to name: the BenQ W2720i at $1,799 in BenQ’s US shop in October 2026 is the better choice for 100–120-inch rooms that do not need this model’s lens shift, with 2,500 rated ANSI lumens, 90% DCI-P3 and only ±5% vertical shift; the BenQ TK710 at $2,199 in the same store in October 2026 is the better pick when bright, fast gaming matters more than 100% DCI-P3 cinema color, with 4.2ms at 1080p/240 and 16.7ms at 4K/60; the Epson Home Cinema 5050UB at $3,799.99 from Epson’s authorized sellers in October 2026 suits a blacked-out theater or someone very sensitive to rainbows, since three-chip LCD has no color-wheel rainbows, at the cost of a replaceable lamp. [3][9][18][19][20]