Professional Tool Reviews for Pros

Hitachi EC99S Twin Stack Compressor Review

HItachi EC99S Twin Stack Compressor
PTR Review
  • Build Quality 10.0
  • Design 9.0
  • Performance 9.0
  • Value 9.0

The team really did a nice job designing the Hitachi EC99S Twin Stack Compressor. Features like the carry handle and 105 on/135 off switch really help with productivity and it has the look and feel of a compressor designed to last.

Overall Score 9.3 (out of 10)

Hitachi is so well known for the quality of their nailers that you’d think compressors would be a natural part of their lineup. While there are several on the market, compressors aren’t the kind of product that you see come out every six months or a year like many cordless tools. When I learned that the Hitachi EC99S Twin Stack Compressor was being launched, I had to get my hands on it to replace the aging pancake model I’d been working with.


Compressors aren’t necessarily the prettiest part of your arsenal, but there’s a lot more going on under the housing in modern units than meets the eye. This mainly takes the form of thermal overload protection and the Hitachi EC99S includes it. Should the motor begin running too hot, it will automatically shut down before it gets hot enough for damage to set in.

Other features are also designed to maintain durability. The 15-amp motor is a direct drive induction design. The regulators include locking mechanisms to ensure the proper pressure is delivered to your tools. Hitachi went with steel encased, industrial level pressure gauges on this model.

One nice feature Hitachi built in is a 105 on/135 off switch. This flips the compressor back on before you start getting too low a pressure and begin firing your nails too shallow.

Many modern small compressors are now oil-free, but the Hitachi EC99S isn’t in that class. The included 15W40  synthetic oil will get you going, however. That feeds into a cast iron pump.

HItachi EC99S Twin Stack Compressor Oil and Dipstick

Non-slip, no mar rubber feet are found on the lower frame. There’s a standard ball valve drain cock at the base of the tank that makes pressure release simple.

Pro Tip

Always drain your compressor at the end of each day. Moisture in the air becomes trapped in the tank and can begin to rust it from the inside – especially if you live near the coast where salt is in the air as well.

Hitachi EC99S Twin Stack Compressor Specifications

  • Model: Hitachi EC99S
  • Power Source: 120V AC
  • Motor: 15-amp, 2.0 horsepower direct drive
  • Max Pressure: 135 PSI
  • Max CFM: 3.1 @ 90 PSI
  • Tank Style: Twin stack
  • Tank Capacity: 4.0 gallons
  • Coupling Sockets: 1
  • Lubrication: 15W40 oil
  • Weight: 52.9 pounds
  • Price: $179.00
  • Warranty: 1 year

First Impressions

Out of the box, the physical design of the Hitachi EC99S struck me. Compressors aren’t normally something you think of as streamlined, but this one looks good. The coloring is nice (matching the pneumatic nailers) and gives it a more subtle look than the bright green found on the cordless tools might offer.

HItachi EC99S Twin Stack Compressor Quick Connect

The carry handle centered above the compressor is as near perfect as you can get for a 53-pound tool. It really makes the compressor easier to handle with one hand, though the weight is still something I’m not in a hurry to pick up and move every ten minutes.

There’s just a single universal quick coupler, so you’ll be working solo with this unit unless you add a splitter. My first thought was that I’d like a to have a second on it, but the reality is that when I’m working on my remodeling projects, I’m usually trimming or framing on my own.

Real World Performance

One of the first things most Pros consider when they turn their compressor on for the first time is the noise level. You have to know what to expect if you’re called out to a school, office building, or other structure that may be occupied while you’re working. The Hitachi EC99S doesn’t claim to be a low noise model, but it’s actually on the quieter side for this class. Just don’t expect it to be quiet enough to work inside while your client catches a Sunday afternoon nap.

HItachi EC99S Twin Stack Compressor Profie

From there it’s all about performance. I love the 105 PSI on switch. At no time did I fall short on air pressure as each nail slammed into pressure treated pine with confidence. You’ll notice that the compressor cycles a little more frequently but for a shorter duration to make it happen.

Recharge rate is solid with this model. From dead empty to 135 PSI, it took just over 1 minute, 20 seconds (1:22 by my watch). Once I drained it to 105 PSI, it filled back up right at 20 seconds.

I read several reviews where users had an issue with the Hitachi EC99S Compressor popping the fuse every time it turned on. All of my work has been off of 20-amp breakers and I haven’t run into this problem so far.

The vibration in this unit seems to be lower than other compressors I’ve used. The direct drive motor and rubber feet certainly help reduce it. The build quality comes across as very solid, so what little vibration is there transfers to the feet where the rubber absorbs it.


The team really did a nice job designing the Hitachi EC99S Twin Stack Compressor. Features like the carry handle and 105 on/135 off switch really help with productivity and it has the look and feel of a compressor designed to last. I think we’d all love our compressors to be an oil-free design. However, I’ll put up with the routine maintenance in order to get the kind of quality that Hitachi seems to have built in to this unit.

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Larry Morris

How far should oil be up on dip stick on ec99s hitachi air compressor

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