By Martin Harris.

1 HP vs 2 HP Dust Collector: Which One You Actually Need

A 1 HP dust collector is enough if you roll it to one machine at a time on a short hose and your biggest tool needs about 400 CFM. Buy a 2 HP collector if you want fixed ductwork, if the collector will sit more than a few feet from your tools, or if you own a drum sander, a planer 15 inches or wider, or a miter saw with a hood. On paper, the 2 HP class has close to three times the airflow. Once hose and duct are attached, the gap shrinks, but it still decides which jobs each size can handle.

HP is horsepower, the size of the motor. CFM is cubic feet per minute, the amount of air the collector moves. If you want a number for your own tool list, my what size dust collector do I need calculator gives you one in a few clicks. This page explains what that number means when you are choosing between the two most common sizes.

Two collectors side by side

To compare fairly, I picked two single-stage bag collectors from the same maker and the same product line. The Grizzly G1163P is a 1 HP unit, and the Grizzly G1029Z2P is its 2 HP sibling. These are the numbers from Grizzly's machine data sheets.

Source: Grizzly Industrial machine data sheets for the G1163P and G1029Z2P. Manufacturer ratings. Delivered airflow is lower.

Two lines matter most. Rated airflow is almost three times higher on the 2 HP unit. Max static pressure is about 50 percent higher. Static pressure is the resistance a fan can pull against, measured in inches of water column (in. w.c.). A collector with more of it keeps moving air through longer hose, more elbows, and finer filters. My guide to dust collector static pressure explains why that second number often matters more than the first.

Rated CFM vs what reaches the tool

Rated CFM is measured with nothing restricting the fan. Max static pressure is measured with the inlet fully blocked, so no air moves at all. Real use falls somewhere in between. Woodcraft's article on dust collection for a one man shop measured airflow through real hose and duct, and it shows what each size does in practice:

Source: Woodcraft, Dust Collection for the One-Man Shop. Different collectors than the Grizzly models above.

On a short hose, the classes are closer than the box suggests. The 1 HP unit delivered about 420 CFM, and the 1.5 HP unit about 500. That is roughly 65 percent of the 1 HP rating and 42 percent of the 1.5 HP rating. Bigger fans lose a larger share of their rated number once any hose is attached.

With longer duct, the bigger motor pulls ahead. The 1 HP collector fell under 300 CFM through a 25 foot run, while the 2 HP collector held 570 CFM through about the same length. The duct material was different in those two runs, PVC for one and metal for the other, so treat it as a rough comparison. The pattern still matches what the static pressure numbers predict.

Match the collector to your tools

Your biggest tool sets the target. Here is how the common tools split, using the recommended figures from my dust collector CFM chart:

• Within reach of a 1 HP on a short hose: cabinet table saw (400), bandsaw (400), router table (350), small benchtop sander (350), drill press (350), and a 6 or 8 inch jointer (400 to 450).
• 2 HP territory: a 15 inch or larger planer (550), drum sander (600+), miter saw with a hood (550+), CNC router (550 to 650), and a cabinet saw with an overarm guard (550 to 600).

A 12 inch planer at 450 CFM sits right on the line. A 1 HP collector with a very short hose can keep up with it for chips. If you plane a lot, or if the planer is where you would want the collector to live, go 2 HP. These figures are for chip pickup and moderate fine dust capture. Bill Pentz, whose research site many woodworkers use as a reference, targets about 1,000 CFM at many stationary tools for aggressive fine dust control, which is beyond both sizes once duct is attached.

Your shop layout decides it too

• One hose, collector on wheels. A 1 HP fits this well. You roll the collector next to the tool and keep the hose short, which is the setup where the 1 HP class does its best. My best portable dust collector picks cover this style.
• Fixed duct to several tools. Go 2 HP. Duct adds length, elbows, and wyes, and each piece eats static pressure. A 1 HP collector with a 7.2 inch maximum has little left for a real duct run.
• Two machines running at once. Neither size does this well. Woodcraft found that a 2 HP collector fell under 300 CFM with two gates open on metal duct, and the article advises looking at 3 HP or bigger if you often run two machines together.
• Tight floor space. The 1 HP Grizzly takes a 14 by 14 inch footprint. The 2 HP model takes about 33 by 21 inches and stands 78 inches tall. Measure your corner and your ceiling height before you order.

Wiring and power

Power is often the real deciding factor in a garage. The 1 HP Grizzly comes wired for 120 volts, draws 7 amps, needs a 15 amp circuit, and plugs into a standard household outlet. It can also be rewired for 240 volts.

The 2 HP Grizzly runs on 240 volts only. It draws 9 amps, needs at least a 15 amp circuit, and uses a 6-15 plug, which has a different blade shape than a household plug. Many garages have no 240 volt outlet. Some 2 HP collectors run on 120 volts, though. Harbor Freight's 2 HP dust collector is built for a 120 volt circuit. Read the manual for the exact circuit size before you buy any collector.

If you need a new 240 volt circuit, hire a licensed electrician. Adding a circuit usually means work inside your electrical panel, and many areas require a permit. My guide to dust collector 240V wiring covers what to ask for so the electrician installs the right outlet the first time.

Filtration is a separate question

Motor size does not decide how much fine dust comes back out of the bag. In the Grizzly pair above, the 1 HP unit ships with a 30 micron bag and the 2 HP unit with a 2.5 micron bag. A micron is a tiny unit of length, 1/25,400 of an inch. Bill Pentz treats particles under 10 microns as the fine, breathable dust, so a 30 micron bag lets a lot of it through. You can upgrade the bag on either size. My comparison of 1 micron vs 5 micron filter bags covers the options.

Upgrades cost static pressure, though. A finer filter resists airflow more than a coarse bag, and Oneida suggests budgeting about 2 in. w.c. for a cyclone separator. On a collector with 7.2 inches of maximum static pressure, a separator and a fine filter take a large share of the total. A 2 HP collector has more room for both.

My recommendation

• Pick 1 HP if you use one tool at a time, you're fine rolling the collector to each machine, your biggest tool needs 450 CFM or less, and you only have 120 volt outlets.
• Pick 2 HP if you want ductwork, you own a tool that needs 550 CFM or more, you plan to add a separator or a finer filter, or you already have a 240 volt circuit (or choose a 120 volt model).
• Look past 2 HP if you run two machines at once, or you want fine dust capture near the Pentz target of 1,000 CFM.

If you land on 2 HP, my best 2 HP dust collector roundup compares the options. One 2 HP option worth a look is the Grizzly G0548ZP 2 HP canister collector, which trades the bag for a pleated canister filter. My Grizzly G0548ZP review has the details. For how the collector choice fits with duct, filters, and air cleaning in a small space, see my complete guide to small shop dust collection.

For specific 1 HP units with listed specs and current prices, see the POWERTEC 1 HP review and the WEN collector review.

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