Concrete is one of the hardest surfaces to clean. Driveways, sidewalks, garage floors, and patios collect oil stains, algae and moss, tyre marks, and deeply embedded dirt. A garden hose — or many lighter electric units — simply can’t remove these problems. For real concrete cleaning, you need a heavy-duty gas pressure washer built for high PSI and high flow. In this SIMPSON vs Generac review, we test the best gas pressure washer for concrete scenarios: driveway cleaning, oil stain removal, and large-area surface cleaning in the U.S.
Why concrete needs a heavy-duty pressure washer
Concrete is porous. Tiny holes trap oil, grime, and organic growth. To flush contaminants out, you need both impact (PSI) and volume (GPM). The practical target for real concrete work is:
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PSI: 3,000–4,000+
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GPM: 2.5–4.0
That combination gives the impact to break stains and the flow to wash debris away — the baseline for any concrete pressure washer that’s going to do a professional job.
Quick summary: winner by use-case
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Generac — best for heavy stains, large driveways, and fast flushing power (higher GPM on many models). Ideal if you need the fastest concrete cleaning and commercial-style performance.
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SIMPSON — best for balanced, controlled cleaning, lower noise, and reliable pump stability. Great as a best pressure washer for concrete driveway for homeowners and light pros.
SIMPSON gas pressure washers — why they work on concrete
Brand & build
SIMPSON is known for durable, jobsite-ready machines. Their models targeted at concrete typically feature:
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PSI: ~3,200–4,000
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GPM: ~2.5–3.5
Engine & pump
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Uses reliable OEM engines with smooth throttle response and easy starts — helpful for long runs.
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Professional-grade pumps that hold steady pressure during extended cleaning sessions.
Real-world concrete performance
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Excellent at repeated, controlled passes on oil stains and textured concrete.
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Pairing with a surface cleaner yields very uniform results without streaking.
Best for: homeowners or contractors who want controlled, repeatable results and easier long-term ownership.
Generac gas pressure washers — why they often edge out on concrete
Brand & build
Generac brings generator-level durability to pressure washers. Typical specs for concrete-focused Generac units:
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PSI: ~3,100–4,200
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GPM: ~2.7–4.0
Engine & pump
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In-house engine designs with higher torque and heat tolerance.
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Pumps built to maintain high flow under load — excellent when using surface cleaners or tackling heavy oil.
Real-world concrete performance
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Faster cleaning on large driveways and industrial areas thanks to higher GPM.
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Often clears organic growth and oil stains in fewer passes.
Best for: heavy users, frequent large-area cleaning, and commercial contractors who prioritise speed.
Head-to-head: PSI, GPM, and cleaning speed
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PSI vs GPM: SIMPSON tends to deliver steadier PSI; Generac tends to deliver higher GPM (flushing power).
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Cleaning speed: Generac usually finishes large concrete areas quicker; SIMPSON delivers a more controlled finish for delicate surfaces.
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Surface-cleaner compatibility: Generac’s higher flow spins surface cleaners faster and covers more ground per minute.
How each brand handles common concrete problems
Oil stains
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Generac: Faster removal on first passes (thanks to higher GPM).
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SIMPSON: Requires more passes but leaves a more even finish.
Algae, moss, black mould
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Both brands perform well; use detergent + hot water or a biocide when necessary.
Large driveways & parking pads
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Generac has a time advantage with surface cleaners; SIMPSON gives tighter control for edges and textured concrete.
Maintenance, longevity, and ownership costs
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SIMPSON strengths: reliable pumps, easier vibration control, typically quieter, good spare-part availability.
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Generac strengths: robust engines, built to take heat and longer workloads — may use more fuel under heavy use.
Both require standard maintenance (oil changes, pump protection, winterising). Expect slightly higher fuel consumption for sustained heavy cleaning with Generac.
Noise & operator comfort
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SIMPSON: generally quieter, lower vibration — better for residential jobs where noise matters.
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Generac: louder, more industrial feel — acceptable for contractors and commercial sites.
Best-use recommendations (choose by workload)
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Choose SIMPSON if you: want smoother, controlled cleaning, lower noise, and long-term stability — ideal as a best pressure washer for concrete driveway in residential settings.
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Choose Generac if you: clean large areas frequently, need maximum speed, and face heavy, embedded stains — the better concrete pressure washer for commercial or heavy-use jobs.
Final verdict
Both brands build excellent gas pressure washers for concrete, but your workload decides the winner:
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Heavy stains, large areas, fast results → Generac (higher flow, more aggressive cleaning).
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Residential driveway, smoother control, comfort → SIMPSON (balanced pressure, quieter operation).
FAQ section
Q: Which is better for concrete — SIMPSON or Generac?
A: For heavy, fast cleaning and large driveways, choose Generac; for controlled, quieter residential cleaning, choose SIMPSON.
Q: What PSI and GPM do I need to clean a concrete driveway?
A: Aim for 3,000–4,000 PSI and 2.5–4.0 GPM for reliable results.
Q: Is a gas pressure washer better than an electric one for concrete?
A: Yes — for driveways and heavy stains, a gas pressure washer with higher PSI and GPM is usually required.
Q: Can I use a surface cleaner with SIMPSON or Generac?
A: Yes — surface cleaners work on both. Generac typically covers more area faster due to higher flow.