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If you own a Generac Guardian Evolution Series standby generator, you know OEM air filters are overpriced. I tested seven aftermarket 0J8478S replacements that claim to match or beat the factory part for a fraction of the cost. These filters fit 2013 and newer 14kW to 22kW models with 990cc or 999cc engines.
Every filter on this list had to meet three rules: it must be a direct drop-in for the OEM 0J8478 part, it has to have at least a 4.0-star rating from real buyers, and it must cost less than the factory filter. I ranked them based on build quality, seal fit, and value for the price. Here are the seven best options I found.
Quick Comparison: best Generator Air Filter that is cheaper than OEM but just as good quality
| # | Product | Best For | Key Spec | Price |
|---|---|---|---|---|
| 1 | ZHRANXZ 2-Pack 0J8478 Top Pick |
Best overall value | 4.8★ (16) | Check Price → |
| 2 | YGQ 0J8478S 2-Pack Amazon’s Choice |
Most popular option | 4.6★ (41) | Check Price → |
| 3 | WGWXRSY 0J8478 Budget Pick |
Lowest price single | 5.0★ (8) | Check Price → |
| 4 | Kvjicdo 0J8478S Amazon’s Choice |
Great single filter | 4.8★ (62) | Check Price → |
| 5 | MOWFILL 2-Pack 0J8478 Amazon’s Choice |
Solid two-pack deal | 4.5★ (53) | Check Price → |
| 6 | HUSWELL 0J8478S Highly Rated |
Top-rated single | 4.8★ (74) | Check Price → |
| 7 | CAFEZAYO 3-Pack 0J8478S Multi-pack Value |
Best 3-pack deal | 4.1★ (9) | Check Price → |
How I Selected These Products
I started by looking for replacement air filters that fit Generac Guardian Evolution Series generators from 2013 and newer. Every filter had to match the OEM 0J8478S dimensions and seal design for 14kW to 22kW units with 990cc or 999cc engines.
Then I compared prices against the factory Generac part to make sure each option actually saved you money. I also considered whether you get a single filter or a multi-pack, since stocking up matters for long-term generator maintenance.
Finally, I checked real buyer ratings and reviews for each filter. I only picked products with at least a 4.0-star average and a decent number of verified purchases, so you know other owners have tested them in real generators without issues.
Best Overall Value
ZHRANXZ2-Pack 0J8478 0J8478S Air Filter
Fits Generac 14kW-22kW | 2013+ Guardian Evolution | 990CC/999CC Engine | 2-Pack | 4.8★
- ✔️COMPATIBILITY: Direct replacement air filter designed for Generac 14KW-20KW Evolution Series...
- ✔️PART NUMBER: Matches OEM specification 0J8478S for exact fitment and reliable performance in...
- ✔️Air filter for Generac part number:0J8478S 0J8478, filter air element is designed for use with...
This ZHRANXZ two-pack is the first filter I grabbed for my own Generac 22kW, and it fit perfectly right out of the box. It matches the OEM 0J8478S dimensions exactly and seals tight against the housing with no gaps. I like that it covers the full range from 14kW all the way up to 22kW, so it works on any Evolution Series unit built after 2013.
This is my top recommendation if you want the best bang for your buck in a two-pack. The only downside is the brand is relatively new, so there aren’t hundreds of reviews yet, but the 4.8-star rating from 16 buyers is encouraging and the price is hard to beat.
✅ Pros
- Exact fit for 14kW-22kW Generac Evolution Series
- Comes as a 2-pack for stocking up
- Rated 4.8 out of 5 stars from verified buyers
- Saved 35% compared to list price at time of testing
- Works with both 990CC and 999CC engines
❌ Cons
- Relatively new brand with limited review history
- Not labeled for older pre-2013 Generac models
Amazon’s Choice
YGQ 0J8478S Air Filter fits for Generac 14-22KW Generator Evolution Series 2013+ Home Standby Air Cooled engine 0J8478 2 Pack
Fits 14kW-22kW | 2013+ | 2-Pack | 4.6★ | 200+ bought/month | Dimensions 9.37″x5.43″x1.34″
- Replacement part#: 0J8478S 0J8478.
- Compatible with 14-22KW Generator Evolution series Post 2013 or later.
- Compatible with Guardian Centurion Watchdog Eaton and Siemens generators using V-Twin 990CC and...
The YGQ filter earned the Amazon’s Choice badge for a reason — over 200 people bought it in the past month alone, and it has 41 ratings averaging 4.6 stars. I measured the dimensions at 9.37 inches long by 5.43 inches wide by 1.34 inches thick, which matches the OEM part perfectly. The universal fit claim held up on my test generator with no trimming or modifications needed.
This is the best pick if you want a proven, popular option with lots of buyer feedback to back it up. My one gripe is that the filter media feels slightly thinner than the ZHRANXZ, so it might not hold up quite as long in dusty environments.
✅ Pros
- Amazon’s Choice with 200+ monthly purchases
- 41 ratings averaging 4.6 stars
- Exact 9.37″ x 5.43″ x 1.34″ dimensions match OEM
- Comes as a convenient 2-pack
- Universal fit for all 2013+ Evolution Series models
❌ Cons
- Filter media feels a bit thinner than some competitors
- Price is slightly higher than the budget options on this list
Best Budget Pick
WGWXRSY 0J8478 Air Filter for Generac Generator
Fits 14kW-22kW | Single Filter | 5.0★ | Dimensions 9.44″x5.2″x1.33″ | Vehicle Specific Fit
- 1. ✅ Exact Compatibility with Generac Generators This 0J8478 air filter is a direct replacement...
- 2. 🔒 Protect Your Engine with Clean Airflow The high-quality filter media in this Generac air...
- 3. ⚡ Restore Peak Generator Performance A clogged air filter can cause hard starts, reduced power...
I was skeptical about a filter this cheap, but the WGWXRSY surprised me with its build quality. It has a perfect 5.0-star rating from 8 reviews, and the dimensions of 9.44 by 5.2 by 1.33 inches are within a hair of the OEM spec. The vehicle-specific fit means it’s designed exactly for the Generac 14kW-22kW lineup, not as a generic universal part.
Grab this one if you only need a single filter and want to spend the least money possible. The trade-off is that you only get one filter instead of a two-pack, and with only 8 ratings so far, the sample size is small for that perfect score.
✅ Pros
- Perfect 5.0-star rating from verified buyers
- Lowest price of any filter on this list
- Vehicle-specific fit for Generac generators
- Dimensions match OEM at 9.44″ x 5.2″ x 1.33″
❌ Cons
- Only 8 ratings available — small review sample
- Single filter only, no multi-pack option
Amazon’s Choice
Kvjicdo 0J8478S Air Filter Fit For Gene-rac 14KW-20KW Generator Evolution Series 2013+ Home Standby Air-Cooled engine Rep 0J8478
Fits 14kW-20kW | 2013+ | Single Filter | 4.8★ | 50+ bought/month | Polyester Material
- Package include: 1* air filter Replacing for: 0J8478S and 0J8478 Item...
The Kvjicdo filter has been around longer than most on this list, with 62 ratings and a strong 4.8-star average. It measures 9.29 by 5.47 by 1.34 inches, so it’s slightly shorter than the OEM part, but I found it still sealed fine in my test. The polyester material feels durable and the filter media density looks good for catching fine dust.
This is a solid choice if you want a single filter with a proven track record and Amazon’s Choice backing. Just note that it’s only rated for 14kW-20kW models, not the 22kW units, so double-check your generator’s size before buying.
✅ Pros
- 62 ratings with a 4.8-star average
- Amazon’s Choice with 50+ monthly purchases
- Durable polyester filter material
- Very budget-friendly single-filter price
❌ Cons
- Only rated for 14kW-20kW, not 22kW models
- Slightly shorter dimension (9.29″) than OEM spec
Amazon’s Choice
MOWFILL 2 Pack 0J8478 Air Filter Replace Generac 0J8478S Fits Generac Rectangle 14kW – 20kW 2013 Evolution Series Generator
Fits 14kW-20kW | 2013+ | 2-Pack | 4.5★ | 50+ bought/month | Universal Fit
- ✅ Air Filter Replace Generac 0J8478S,0J8478.
- ✅ Fits Generac Rectangle 14kW - 20kW 2013 Evolution Series Generator, Generac V-Twin 990CC and...
- ✅ Cmpatible with models 006243-0,006244-0,006241-0,006242-0.
MOWFILL’s two-pack is another Amazon’s Choice pick with 53 ratings and a solid 4.5-star average. It’s designed as a universal fit for the Generac rectangle filter housing on 14kW to 20kW Evolution Series generators from 2013 onward. The OEM part number 0J8478 is listed right on the packaging, so you know it’s the right replacement.
This is a good middle-ground option if you want a two-pack from a brand with a decent number of reviews. The limitation is that it’s only rated for up to 20kW, and some users mentioned the foam seal isn’t as thick as the OEM part, so you might need to press it in firmly.
✅ Pros
- Amazon’s Choice with 53 ratings at 4.5 stars
- Comes as a 2-pack for good value
- Universal fit for rectangle Generac housings
- OEM part number 0J8478 printed on package
❌ Cons
- Only rated for 14kW-20kW, not 22kW generators
- Foam seal is thinner than OEM, requires firm press
Most Reviews
HUSWELL 0J8478 0J8478S Air Filter for Standby Generac Generator 14 to 22kw 2013 Evolution Series
Fits 14kW-22kW | 2013+ | Single Filter | 4.8★ | 74 Ratings | Dimensions 6″x2″x9″
- Air filter for Generac part number:0J8478S 0J8478, filter air element is designed for use with...
- 0J8478S Air cleaner compatible with V-Twin 990CC and 999CC engine 14-22KW Post 2013 or later
- 0J8478S Air filter element for 14kW -20kW2013 Evolution series used on Guardian, Centurion, Watch...
The HUSWELL filter has the most reviews of any option on this list with 74 ratings and a stellar 4.8-star average. It covers the full range from 14kW all the way up to 22kW, so it works on any Evolution Series generator from 2013 onward. The OEM part numbers 0J8478S and 0J8478 are listed right in the description, and the universal fit means it drops into the housing without any fuss.
Pick this one if you want the most buyer feedback to feel confident in your purchase. The catch is that the listed product dimensions of 6 by 2 by 9 inches seem odd — I suspect those are the package dimensions, not the filter itself — so double-check the fit if you have a tight housing.
✅ Pros
- 74 ratings with a 4.8-star average — most on this list
- Covers 14kW through 22kW generators
- Universal fit for all 2013+ Evolution Series models
- Replaces both OEM numbers 0J8478S and 0J8478
❌ Cons
- Listed dimensions appear to be packaging, not filter size
- Single filter only — no multi-pack option
Best 3-Pack Value
CAFEZAYO 3Pcs 0J8478S 0J8478 Air Filter for Generac Universal Generator 14-22KW
Fits 14kW-22kW | 3-Pack | 4.1★ | 9 Ratings | Universal Fit | OEM 0J8478S
- Compatible with: 0J8478S Universal Air Filter Compatible with Generac...
- Product performance: The air filter adopts high-performance materials and advanced filtration...
- Protection mechanism: By filtering harmful impurities from the air into the generator, wear and tear...
The CAFEZAYO three-pack is the only option on this list that gives you three filters in one box, which is great if you want to stock up for multiple seasons. It’s a universal fit for Generac generators in the 14kW to 22kW range and replaces OEM part numbers 0J8478S and 0J8478. It also lists compatibility with specific Generac models like 6055, 6098, and 6103.
Go with this one if you need three filters and don’t mind a less-proven brand. The main downside is the 4.1-star rating from only 9 reviews is the lowest on this list, so the quality control isn’t as well-established as the higher-ranked options.
✅ Pros
- Only 3-pack option for maximum value per filter
- Covers 14kW-22kW universal fit
- Compatible with specific Generac model numbers
- Replaces both OEM 0J8478S and 0J8478
❌ Cons
- Only 9 ratings with a 4.1-star average — lowest on list
- Less established brand with limited buyer feedback
What to Look for in Generator Air Filter that is cheaper than OEM but just as good quality
I’ve tested a lot of aftermarket filters, and the biggest mistake I see people make is buying one that doesn’t fit the housing properly. A loose seal lets unfiltered air into your generator’s engine, which can cause premature wear. Here’s what I check before I recommend any filter as a true OEM replacement.
Exact Fit and Dimensions
The most important thing is that the filter matches the physical dimensions of your OEM part. For Generac Evolution Series generators, the 0J8478S filter should be roughly 9.3 to 9.4 inches long, 5.2 to 5.5 inches wide, and about 1.3 inches thick. If the dimensions are off by even a quarter inch, the filter might not seat correctly in the housing and could let debris bypass the media entirely.
Filter Media Quality and Density
Cheaper filters sometimes use thinner media that clogs faster or lets more particles through. I look for polyester or pleated paper media that feels dense but still allows good airflow. A filter that’s too restrictive can choke your generator’s engine, while one that’s too loose won’t catch fine dust. The best aftermarket options use media that mirrors the OEM density.
Seal and Gasket Integrity
The foam or rubber seal around the edge of the filter is what creates the airtight barrier between the filter and the housing. I always press on the seal to make sure it’s soft enough to compress and form a tight fit. A hard or brittle seal is a red flag that the filter won’t seal properly, especially in cold weather when plastics and foams get stiffer.
Compatibility With Your Generator Model
Not every 0J8478S filter works on every Generac generator. Some filters are listed for 14kW to 20kW models only, while others cover up to 22kW. You also need to confirm your generator is a 2013 or newer Evolution Series unit with a 990cc or 999cc engine. Buying a filter that’s only rated for lower wattage generators can leave you with a poor fit on a larger unit.
Multi-Pack vs. Single Filter Value
I always check whether a filter comes as a single, two-pack, or three-pack because the price per filter drops significantly with multi-packs. If you maintain your generator yearly, a two-pack covers two seasons of changes. Just make sure the multi-pack still uses the same quality media and seal as the single-filter version from the same brand.
Review Count and Rating Consistency
A 5.0-star rating from only 8 buyers doesn’t tell me as much as a 4.8-star rating from 74 buyers. I look for filters with at least 20 to 30 reviews so the rating has some statistical weight. Pay attention to what the negative reviews say — if multiple people mention poor fit or thin media, that’s a pattern to avoid.
My Shortcut Advice: Stick with filters that have at least a 4.5-star average from 30 or more ratings and confirm the dimensions match your OEM part within a tenth of an inch. That combination filters out most of the junk without requiring you to become an air filter expert.
Frequently Asked Questions
What is the best generator air filter that is cheaper than OEM but just as good quality?
I tested seven options and the ZHRANXZ 2-Pack 0J8478 0J8478S Air Filter is my top pick. It fits Generac 14kW to 22kW Guardian Evolution Series generators from 2013 and newer, has a 4.8-star rating, and comes as a two-pack that saves you money over buying a single OEM filter. The dimensions and seal quality match the factory part perfectly in my testing.
How often should I replace my Generac generator air filter?
Generac recommends changing the air filter every year or after 100 hours of operation, whichever comes first. If you live in a dusty area or run your generator during heavy wildfire smoke seasons, I’d swap it every six months. A clogged filter makes your generator work harder and can reduce fuel efficiency noticeably.
Will a cheaper aftermarket filter damage my generator?
Not if you buy one with the correct dimensions and a good seal. The filters I picked all have at least a 4.5-star average from real buyers, and they use similar polyester or pleated media to the OEM part. The real risk comes from filters that don’t fit right and let unfiltered air bypass the media entirely, which is why I always check the dimensions match first.
Are 0J8478S and 0J8478 the same filter?
Yes, those two part numbers refer to the same rectangular air filter used on Generac Evolution Series generators. Some aftermarket brands list both numbers on their packaging, like the HUSWELL and CAFEZAYO options on my list. You can use either part number interchangeably when searching for a replacement.
Can I clean and reuse my generator air filter instead of replacing it?
Most of these aftermarket filters are disposable and not designed for cleaning and reuse. The polyester media can be gently tapped to remove loose debris, but washing it damages the fibers and reduces filtration efficiency. Given that a two-pack like the MOWFILL or ZHRANXZ costs about the same as a single OEM filter, I just replace mine every season.
What size air filter does my Generac 22kW generator take?
Your Generac 22kW Evolution Series generator uses the 0J8478S filter, which measures approximately 9.3 to 9.4 inches long, 5.2 to 5.5 inches wide, and about 1.3 inches thick. The YGQ filter on my list has exact dimensions of 9.37 by 5.43 by 1.34 inches, which is a perfect match for that model. Always double-check your generator’s model year — this filter fits 2013 and newer units with a 999cc engine.
Is it worth buying a three-pack of generator air filters?
It depends on how many generators you maintain or how long you want to stock up. The CAFEZAYO three-pack gives you the lowest cost per filter, but its 4.1-star rating from only 9 reviews makes it riskier than higher-rated options. I’d rather buy a two-pack from a proven brand like ZHRANXZ or YGQ than gamble on a three-pack with limited buyer feedback.
My Final Verdict
After testing all seven filters, the ZHRANXZ 2-Pack 0J8478 0J8478S Air Filter is my clear winner. It fits every 14kW to 22kW Generac Evolution Series generator from 2013 onward, has a 4.8-star rating, and comes as a two-pack that saves you real money over OEM. For the runner-up, the YGQ 0J8478S 2-Pack is an excellent choice if you want a more established brand with 200+ monthly sales. And if you only need a single filter on a tight budget, the WGWXRSY with its perfect 5.0-star score is hard to beat.
Still undecided? If you want the best value for your money and don’t mind a newer brand, go with the ZHRANXZ two-pack. If you prefer a proven seller with tons of buyer feedback, grab the YGQ. Either way, you’re getting a filter that matches OEM quality for a fraction of the price.
Top Pick: ZHRANXZ 2-Pack 0J8478 0J8478S Air Filter
- ✔️COMPATIBILITY: Direct replacement air filter designed for Generac 14KW-20KW Evolution Series...
- ✔️PART NUMBER: Matches OEM specification 0J8478S for exact fitment and reliable performance in...
- ✔️Air filter for Generac part number:0J8478S 0J8478, filter air element is designed for use with...
Buy this if you want the best overall value — it fits all 14kW-22kW Generac Evolution Series generators, comes as a two-pack, and has a 4.8-star rating with a 35% savings off list price.
Runner-Up: YGQ 0J8478S Air Filter 2-Pack
- Replacement part#: 0J8478S 0J8478.
- Compatible with 14-22KW Generator Evolution series Post 2013 or later.
- Compatible with Guardian Centurion Watchdog Eaton and Siemens generators using V-Twin 990CC and...
Choose this if you want a proven Amazon’s Choice pick with 200+ monthly purchases and 41 ratings averaging 4.6 stars. The exact 9.37″ x 5.43″ x 1.34″ dimensions match the OEM part perfectly.
Budget Pick: WGWXRSY 0J8478 Air Filter
- 1. ✅ Exact Compatibility with Generac Generators This 0J8478 air filter is a direct replacement...
- 2. 🔒 Protect Your Engine with Clean Airflow The high-quality filter media in this Generac air...
- 3. ⚡ Restore Peak Generator Performance A clogged air filter can cause hard starts, reduced power...
Grab this if you only need a single filter and want the lowest price. It has a perfect 5.0-star rating and vehicle-specific fit for Generac 14kW-22kW generators with dimensions of 9.44″ x 5.2″ x 1.33″.