GarageVac byInterVac

Buyer's guide

Most of the numbers on a vacuum box are not measurements.

Peak horsepower, watts, kPa, CFM, air watts. Four of those describe something real. One of them describes almost nothing, and it is the one printed largest. Here is how to tell them apart in about five minutes.

InterVac Design Corp · Palm City, Florida

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The wall decides. Not the box.

Before comparing any two vacuums, there is one piece of arithmetic that settles a surprising number of arguments: a vacuum cannot deliver more power than the outlet gives it.

A standard North American household circuit is 120 volts. Multiply volts by amps and you get watts — the total electricity available. Divide by 745.7 and you get horsepower. That result is the ceiling before the motor turns any of it into heat, noise and vibration, which is where most of it actually goes.

1320WElectricity available
1.77hpCeiling, before any losses
~1.2hpRealistic at the shaft
3.7×Claim vs the ceiling

Even on a dedicated 15-amp circuit — 1,800 watts — the absolute ceiling is 2.4 horsepower of electricity, and a real motor never converts all of it. So when a wet/dry vacuum that plugs into a normal outlet is sold as 5, 6 or 6.5 horsepower, that figure is not describing anything the machine does in your garage. It cannot. The wall will not supply it.

Nobody defines this number

Air watts, water lift and airflow all have established test methods behind them. "Peak horsepower" has none. No standards body specifies how it must be measured, no regulator requires it to mean anything in particular, and there is no obligation on a manufacturer to state the conditions the figure was taken under.

A number with no definition cannot be compared between two products, because the two companies quoting it are not necessarily measuring the same thing. That is not a conspiracy — it is just what happens to a figure nobody is required to standardise. The arithmetic above is the only check available to you, and it is enough.

The five numbers

What each one actually measures

Listed worst to best — by how much each tells you about cleaning your garage.

Peak horsepower

HP · unregulated

A momentary output figure, typically taken on a bench with the motor unrestricted — no hose, no filter, no bag — at a draw the machine never sustains in use. No standards body defines how it must be measured, which is why the numbers drifted upward for years.

It describes a condition that does not exist while you are vacuuming.

Tell If horsepower is the biggest number on the box and no air-watt figure appears anywhere, the horsepower is doing the work that a real measurement would have done.

Watts / amps

W or A · input

What the motor draws out of your wall. This is a measure of consumption, not of performance — the electric bill, not the result. Two vacuums drawing identical wattage can differ enormously in what reaches the end of the hose, depending on the air path, the filter and the seal quality.

Useful for one thing: checking the unit will not trip your circuit.

Tell A higher wattage with no airflow figure often means power is being lost inside the machine, not delivered at the nozzle.

Sealed suction

inches of water lift · kPa · Pa

How hard the machine pulls with the end of the hose completely blocked. It is a real, standardized measurement and it matters — it is what lifts a coin off a floor mat or pulls sand out of carpet pile.

But it is measured at zero airflow, which is not how anyone vacuums. A machine can post strong sealed suction and still move very little air once the hose is open.

Convert freely 1 inch of water lift = 249.09 Pa. So 110″ of water lift is 27.4 kPa. Any two products quoting either unit can be compared directly — see the converter below.

Airflow

CFM · cubic feet per minute

The volume of air moved per minute. Airflow is what carries debris up the hose once it has been lifted. High suction with low airflow gives you a machine that grips but does not clear.

Also a real measurement — but on its own it is only half the picture, and it is usually quoted at the motor rather than at the end of a hose with a filter and bag fitted.

Ask Measured where — at the motor, or at the end of the hose with everything installed? The two figures are not close.

Air watts

AW · the useful one

Suction and airflow combined into a single figure describing work delivered — at the end of the hose, with the filter and the bag in place. It is the closest thing the industry has to a measure of what the machine actually does for you.

It is also the one number that a bigger motor alone will not raise. Restrict the air path, use a filter that chokes, seal the joints badly, and air watts falls no matter how many watts you feed it. That property is exactly what makes it useful to a buyer — and exactly what makes it inconvenient to publish if the design does not support it.

The question that ends the comparison "What is your air-watt rating?" It costs a manufacturer a morning on a test rig to answer.

Free tool

Suction unit converter

Manufacturers quote sealed suction in whichever unit flatters them — inches of water lift in North America, kilopascals almost everywhere else. They measure the same thing. Put in whatever a spec sheet gives you and compare like for like.

110inches H₂O
27.4kPa
27,400Pa
3.97PSI
274mbar

Before you buy

Five questions worth emailing a manufacturer

Any of these can be answered in a sentence by a company that knows its own product. Watch what happens when one cannot be.

  1. 1What is the air-watt rating? If the answer is a wattage or a horsepower figure, the question was not answered.
  2. 2What micron does the filtration actually capture, and is that a HEPA-rated element or HEPA-style? "HEPA" without a micron figure is a word, not a specification.
  3. 3How far does the unit project from the wall, and what does it weigh? Both determine whether it can live in a two-car garage without being in the way — and neither is usually printed.
  4. 4What does emptying it involve? A sealed bag leaves the machine closed. A bin or a reusable cloth bag has to be opened, and whatever you collected goes back into the air of the room you are standing in.
  5. 5Where is it manufactured, and where do replacement parts ship from? "Designed in the USA" and "made in the USA" are different claims, and the second one has rules attached.

For the record, here are ours

514 air watts. 110″ water lift (27.4 kPa). HEPA-type filtration rated to 0.3 micron. Projects 4″ from the wall. 9 lb. Sealed disposable bag, roughly four months per bag. Housing injection-molded in Palm City, Florida; some components sourced globally. Parts ship from the same building.

We publish these because we can. If a competitor publishes an air-watt figure, send it to us and it goes straight into our comparison table — that table exists to be kept accurate, not to be won.

Further reading, including InterVac's own write-ups on this: why horsepower ratings are misleading and why horsepower isn't relevant to vacuums.

Now go compare something.

Our numbers are on the table next to three competitors', with every source dated.

See the comparison →