The DEWALT 18/20V MAX is an interesting machine that has many innovations that would otherwise be quite appealing except that the machine isn't very good at, well, vacuuming. The MAX struggled in both the wet and dry vacuuming analyses, as well as much of the convenience evaluation. That said, this machine does have one heck of a battery life, and it accommodates both 18 and 20-volt batteries. However, it is so poor at picking-up unwanted debris that the value of these components is moot.
DEWALT DCV581H Review
Pros: Long battery life, HEPA rated filter, well-designed floor attachment
Cons: Poor suction, poor airflow, loud
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Our Analysis and Test Results
The main features that make this model a standout in its cohort are its effective floor tool attachment, long runtime, a battery adaptor that allows one to use either an 18 or 20-volt DEWALT battery cell and an auxiliary power cord. Unfortunately, the accolades stop there. More notable is this model's exceptionally poor suction and airflow, which means it's not very good at vacuuming. Added to the poor vacuuming is a super-high price, providing good reasons to look elsewhere for a cordless shop vacuum.
At 39 minutes, 40 seconds of runtime on a 20-volt, 5 amp-hour battery, the DEWALT 18/20V MAX offers one of the longest-lived batteries in the class. A real positive to be sure. It's also an advantage that the machine has an 18-volt adaptor that will allow the user to run either battery type. Additionally, the DEWALT has an auxiliary power cord — a nice touch for prolonged jobs.
Another advantage that the DEWALT offers is a floor attachment tool that works well on hard surfaces. Despite this model's minimal suction and airflow, the gaps in the contact surface of this attachment allow the air to keep moving, and the unwanted liquid or debris to shoot up into the canister.
The overriding problem with the 18/20V MAX is that its motor is greatly underpowered for the tasks it's intended to tackle. We could go into all the vacuuming tests that this machine flopped. However, it's more telling to state the machine's suction and airflow stats. We tested the unit's suction — which is measured in the number of cubic inches of water lift the motor can produce. The DEWALT checked in at an abysmal 16 inches water lift. Yikes!
This machine's airflow is also quite low. The manufacturer's rating is 31 cubic feet per second, a rate that is at the bottom of the class. Contrary to popular belief, suction alone does not a good vacuum make. It is the combination of suction and airflow that moves unwanted items from the floor up into the vacuum canister. So, the fact that this model has poor suction and airflow goes a long way in explaining why it performed poorly in the majority of our wet and dry vacuuming evaluations.
To put it bluntly, we do not find the DEWALT 18/20V MAX to be a very good deal. This machine is at the top of the class in price, but it is at the bottom of the class in performance. Many models on the cordless wet/dry vacuum market cost less and clean better.
The DEWALT 18/20V MAX is a sharp-looking machine with the option of using either an 18 or 20-volt DEWALT battery cell or an auxiliary power cord. It also has an effective floor attachment that works well on hard surfaces where the competition flounders. However, these features do little to mitigate this machine's utter lack of vacuuming power. Exacerbating this performance shortfall is a hefty price tag. It is our opinion that one can do much better than this machine for a lot less money.
— Nick Miley and Austin Palmer