When it comes to HID lighting, the ballast is one of the most misunderstood components in the entire system. We get questions about them constantly, so we pulled a range of units off our shelves (from budget options all the way up to OEM Denso, Mitsubishi, and Matsushita ballasts, plus the Morimoto XP35 and XP55) to break down what actually separates a good ballast from a bad one. At the end of the day they all do the same fundamental thing, but that does not mean they perform the same or carry the same level of quality. This hid ballast comparison is our hands-on look at what matters and why.
What an HID Ballast Actually Does
Let’s start with the basics because it frames everything else. Every ballast we tested takes a 12 volt input from your vehicle and produces a high voltage output that fires and sustains an HID xenon bulb. That is the job. Whether you are running a bargain unit or a premium OEM ballast, the underlying task is identical. Where they differ is in warmup speed, hot restrike capability, weather resistance, efficiency, and how accurate they are in terms of actual light output. Depending on what you spend, all of those variables can swing quite a bit.
At TRS we carry a wide range, everything from really affordable low end ballasts to the Morimoto XP35 and XP55, Mitsubishi’s fourth gen D2S ballasts, Denso’s classic D2S slim ballast, and the Matsushita (Panasonic) gen four ballast as well. Having them side by side is the best way to understand the tradeoffs. If you are shopping for a factory-style replacement, you can browse our OEM HID ballast replacements (Matsushita, Denso, Mitsubishi) to see the exact units we reference here.
Weather Resistance: Why OEM Ballasts Are Not Waterproof Out of the Box
Here is the first thing a lot of people miss. All the original equipment ballasts were designed to be mounted underneath or within an original equipment headlight assembly. Because of that, they do not have much resistance against moisture intrusion on their own. They were never intended to sit exposed in an engine bay. If you mount one somewhere it can get wet, you are asking for trouble unless you take extra steps.
We can get around that limitation by potting the ballast, which is something we offer. Potting extends the warranty and basically makes them bombproof against moisture. But they do not come that way out of the box, so you have to be aware of where you mount them. The Morimoto XB35 and XB55 ballasts are a different story. They are 100 percent potted and waterproof right out of the box, which is exactly what you want if the ballast might end up somewhere damp.
Generic aftermarket ballasts are hit or miss on this front. Sometimes the case is waterproof but there is no potting inside, so it is not really the most reliable setup. That is one of the reasons we lean on units we can vouch for. If you want to compare potted options directly, you can shop aftermarket HID ballasts and see which ones come sealed from the factory.
Reliability and Serviceability
A ballast is a high voltage device, and any electronics placed in a harsh environment (under the hood, subject to heat and vibration) are subject to failure. The good news is that the reliable units are genuinely reliable. The OEM ballasts we carry rarely need replacement for anything outside of moisture damage. They are designed for original equipment manufacturers to last around 2,000 hours, and unless something major happens to them, they pretty much keep going.
The XP35 and XP55 ballasts, even though they are aftermarket, are also super reliable. We have been selling them since November, and in that time they have settled at a failure rate of about 0.06 percent. That is extremely low for an aftermarket ballast, and it is out of roughly 50,000 ballasts already sold. Compare that to the typical no-name aftermarket ballast that comes with zero warranty, and the difference in confidence is night and day. You pay for what you get.
The Two Main Components: Ballast Computer and Igniter
Inside every ballast there are two main components: the ballast computer and the igniter. The ballast computer is what lives inside the big shell. The igniter is the part that produces the high voltage to strike the bulb. On most units, the igniter sits externally. The Denso is one exception, as it houses the igniter inside. But any OEM ballast or well-designed aftermarket ballast with an external igniter is built so that igniter is replaceable, because it is the part that produces high voltage and is therefore more subject to failure.
On the Matsushita it is replaceable, on the Mitsubishi it is replaceable, and on the Morimoto ballast it is replaceable too. On a cheap aftermarket ballast with a non-replaceable igniter, once that igniter goes bad you are out of luck. That single design choice can be the difference between a quick fix and tossing the whole unit. If you want to go deeper on matching igniters to bulbs, our guide to HID ignitor compatibility covers the details.
Swappable Igniters on the Morimoto Ballast
One thing we really like about the Morimoto ballast is that because the igniter is replaceable, there are two different versions available. One is made for D2S bulbs and the other is made for H series bulbs. Both are directly compatible with the same ballast computer, so if you decide to change your setup down the road, you can swap igniters instead of buying an entirely new ballast.
That flexibility is genuinely useful for anyone who bounces between projects or changes bulb types. It is a level of adaptability you simply do not get from a factory ballast, which is locked to whatever configuration the automaker chose.
Wattage Output: 35 Watt OEM vs Higher Output Aftermarket
For people customizing headlights, the ability to choose a higher output ballast (such as a 50 or 55 watt unit) is often a big draw. You are never going to get that from an OEM ballast like the Matsushita, Denso, or Mitsubishi. Those are fixed at 35 watts. If you want more output, you have to look to an aftermarket ballast.
The Morimoto standard XP35 is 35 watts, just like the OEM units. If you want more output, you look to the XP55. The same goes for generic aftermarket ballasts. It is very common to see 55 watt aftermarket ballasts advertised, but whether or not they are accurate in terms of that output is hit or miss. With a cheap high wattage ballast, you might realistically see anywhere from 40 to 50 watts of actual output rather than the number on the box. That is why matching a quality computer to a quality igniter matters so much. If you want the reliable 35 watt route, the AMP: XB35 2.0 35w HID Ballast is a solid pick, and for the higher output option you can check the D2S: XB55 2.0 50w Ballast on Morimoto’s site.
Hot Restrike Capability
When we talked about igniters earlier, one of the most important factors is the amount of voltage that igniter produces. In cold weather, the natural capability of an igniter is decreased because of the low temperature. That is why it is important to make sure you are getting a ballast with a strong enough igniter. A good way to judge that is hot restrike capability.
Hot restrike refers to an igniter’s ability to refire an already hot HID bulb after it has been turned on and off repetitively. That is genuinely hard for a ballast to do. To demonstrate it, we compared a well-known OEM ballast like the Matsushita against the Morimoto and simply flashed them on and off frequently to show the strength of the igniters on each.
If you have ever flashed your high beams and noticed the HID bulb hesitate to relight, that is hot restrike in action. A stronger igniter refires faster and more consistently, and it holds up better when temperatures drop. It is one of the least discussed but most practical measures of ballast quality.
Which Ballast Is Right for You?
If your goal is a factory-faithful replacement that mounts inside the headlight housing and lasts for years, the OEM Denso, Mitsubishi, and Matsushita units are proven performers. Just remember they are not waterproof unless potted, and they are locked at 35 watts. For a plug-and-play OEM-style system, the Denso/Matsushita D2S OEM HID System at Headlight Revolution is a good reference for what a complete factory-grade kit looks like.
If you want out-of-the-box waterproofing, a swappable igniter for D2S or H series bulbs, and the option for higher wattage, the Morimoto XP35 and XP55 make a strong case. With a 0.06 percent failure rate across roughly 50,000 units, they have earned our trust in a way most aftermarket ballasts never do. Whichever direction you go, buy the ballast to match how you plan to mount it and how much output your build actually needs.
Frequently Asked Questions
What does an HID ballast actually do?
An HID ballast takes a 12 volt input from the vehicle and converts it into a high voltage output needed to power an HID xenon bulb.
Are OEM HID ballasts waterproof out of the box?
No, OEM ballasts like those from Denso, Mitsubishi, and Matsushita were designed to be mounted inside an original headlight assembly, so they do not have built in moisture resistance unless they are potted separately.
What is hot restrike capability and why does it matter?
Hot restrike capability refers to a ballast igniter’s ability to refire an already hot HID bulb after it has been turned on and off repeatedly, which is difficult to do and depends on the strength of the igniter, especially in cold weather.
Can aftermarket ballasts provide higher wattage output than OEM ballasts?
Yes, OEM ballasts like the Matsushita, Denso, and Mitsubishi units are fixed at 35 watts, but aftermarket options like the Morimoto XP55 offer higher wattage output, and many generic 55 watt aftermarket ballasts exist though their actual output accuracy varies.
Is the igniter replaceable on the Morimoto ballast?
Yes, the Morimoto ballast has a replaceable external igniter, and there are two versions available, one for D2S bulbs and one for H series bulbs, both of which are directly compatible with the same ballast computer.
Meet the Experts Behind The Retrofit Source
Tyler Jordan – Technical Writer
Tyler works directly with the TRS product R&D team, bringing over a decade of automotive aftermarket lighting experience to every article. An avid enthusiast with hundreds of personal installations under his belt, his content is built on hands-on knowledge from the workbench, not spec sheets.
Caleb Morgan – Marketing Manager
Caleb brings over a decade of automotive lighting industry experience and works with TRS customers daily on the front lines. With hundreds of personal lighting installations and a direct feedback loop from real buyers, his content addresses the questions and problems that actually matter.
