Where 28 Joules Comes From: We Put the Ulike Air 10 on a Power Meter and Measured It

In all the years of IPL contract manufacturing, clients ask about energy almost every day. The market is full of brands shouting 28 joules, 32 joules, even higher — each one louder than the last, and it does sound intimidating. But an energy number only means something next to the treatment window; look at the number alone and you can’t compare across devices. Picking a machine by the biggest number alone leads customers astray — and in the worst case, it can make them suffer for it.

This claim is backed by real measurements. We didn’t just read spec sheets. We bought a Ulike Air 10 — the acknowledged benchmark model on the market — and put it on an Ophir Nova II laser power and energy meter. The instrument’s screen is still a 320x240 black-and-white LCD and it looks unimpressive, but it’s what laboratories and manufacturing plants around the world use to measure energy. After the test, our view on energy changed.

The Numbers We Actually Measured

The Ulike Air 10’s advertised energy is genuinely high. Here’s what we measured across its four levels.

Level	Measured Energy (Joules)
Level 1	9.50 J
Level 2	14.93 J
Level 3	17.74 J
Level 4 (SHR)	29.60 J

Focus on level 4. The 29.60 joules that jumped up on the meter is the total energy of four rapid flashes added together. In SHR (Super Hair Removal) mode, every trigger fires four pulses in a row. The brand takes that sum for its marketing number, claiming a maximum of 28 joules; we measured 29.6. What they usually don’t make clear is that this figure adds four flashes together — a completely different concept from the energy of a single flash.

Is that misleading? To put it politely, it’s creative marketing. And it works: consumers buy machines by the big number.

The Metric That Matters Is Energy Density (J/cm²)

The energy density math works differently. When dermatologists and clinical researchers talk about IPL efficacy, their unit is energy density — the energy actually delivered per square centimeter of skin. Total joules don’t even make the list in their discussions.

The reason isn’t hard to grasp. A machine that puts out 30 joules with a large treatment window spreads the energy out, so each square centimeter gets less. Another machine with only 20 joules total but a small window can deliver more per square centimeter.

There’s exactly one formula: energy density (J/cm²) equals total energy (J) divided by the treatment window area (cm²).

Energy density determines how much intensity the light still has when it reaches the follicle — enough to push the follicle into the catagen phase or not. Only when the follicle enters catagen does hair actually reduce. Clinical studies show a single low-fluence IPL pulse of about 9 J/cm² can trigger this transition. Home device data shows persistent hair reduction of up to 80% one year after the final treatment.

How High Should Energy Go?

Most brands won’t volunteer this: too much energy hurts.

The human pain threshold for IPL is real. In clinical treatments, certain procedures use fluences of 16 to 29 J/cm² — but that’s trained professionals operating, with cooling systems and precise control. Even then, the 14 to 22 J/cm² range needs careful management.

At home, with no professional watching, pushing energy too high brings two problems. One is pain: if the user is in too much discomfort to keep going, the machine’s energy means nothing — an unfinished course is wasted. The other is risk: when energy exceeds what the user’s skin type can take, burns, blistering, and hyperpigmentation are all side effects recorded in the literature.

A 2022 systematic review states the conclusion clearly. It included 37 clinical trials, 19 of them randomized controlled trials, and explicitly recommends home IPL for hair removal, with few adverse events across all devices. A well-designed IPL is safe and effective — the key is the balance between efficacy and safety. The devices with the best outcomes tend to be the ones users can tolerate and keep using. The machine with the biggest number doesn’t necessarily have the best outcome.

Real feedback from our clients lands in the same range. For most users, even with sapphire cooling, the maximum total output they can tolerate is around 18 to 19 joules. Push past that and the cooling can’t hold back the discomfort — sticking with the course becomes hard.

Some brands keep pushing higher. What they’re fighting for is a war on the spec sheet. Brand owners can weigh it themselves: do you want to sell a machine customers actually finish the course with, or a machine customers are afraid to turn on?

How to Spot Inflated Energy Claims

When vetting IPL suppliers, keep an eye out for these three signals.

First, total energy reported without window size. A brand reports 28 joules but won’t tell you the treatment window size — that’s basically hiding the energy density. Push for the J/cm² at each energy level.

Second, combined multi-pulse marketing. The Ulike Air 10 is a ready-made example — the energy of several flashes summed into one advertised number. Ask whether that figure is per single flash or per whole burst.

Third, no independent test data. Anyone can write numbers on a spec sheet. Ask to see optical output reports measured with a calibrated power meter — like the Ophir Nova II we use. If they can’t produce one, they’re probably not measuring the number they advertise.

The FDA has explicit labeling requirements. Section 502 of the Federal Food, Drug, and Cosmetic Act puts it directly: if a label is false or misleading in any respect, the device is deemed misbranded. Yet many brands still operate in the gray zone, reporting an impressive-sounding total energy that reflects neither real performance nor real safety.

What We Do

iShine doesn’t play the numbers game. Our machines are all tested on professional equipment — the same Ophir Nova II we used to measure the Ulike Air 10. We report the true single-flash energy output, and the energy density is calculated properly against the actual window area.

We also listen to real users. Feedback from thousands of consumers points to the same conclusion: total output beyond 18 to 19 joules brings more discomfort than benefit. That’s why our maximum output is set around 18 joules. We could build higher — but after testing and asking around, this is the position where efficacy and comfort both hold up.

Sapphire contact cooling is standard on our machines; studies show it noticeably improves comfort during treatment. Cooling presses the skin surface temperature down, energy goes into the skin as usual, and thermal damage to the epidermis is minimized.

The result is a machine that works — and one users are genuinely willing to keep using.

A Few Last Words

If you’re building a brand and choosing an IPL manufacturing partner, don’t let the biggest number on the spec sheet carry you away. Four questions are worth asking face to face.

• What’s the energy density (J/cm²), or are you only quoting a total joule figure?
• Was that number measured per single flash, or summed across a whole burst?
• What independent testing has been done?
• What do real users say about comfort and whether they can finish the course?

The brands that win over the long term deliver results their customers can tolerate and keep using. However flashy the number, it’s worthless if the customer can’t keep going.

iShine has tested all the leading models on the market. We know what they measure — and what they don’t say. Our machines are built on real data and real user feedback. If you want to compete with Ulike, we probably know more about their energy output than most of their own customers.