The right air filter keeps your AC healthy. Here's exactly what we recommend — and why
The filter is the single easiest thing a homeowner can do to protect their HVAC system. Wrong filter, wrong schedule, or no filter at all — and you’re looking at dirty coils, reduced airflow, and repairs that didn’t need to happen. Here’s what to buy, how to read the ratings, and when to change it.
What We Recommend - Standard white pleated filter, MERV 8 to MERV 10. That's it.
We get asked about filters constantly. Customers want the best possible filtration — and that’s understandable. But the filter with the highest rating is not always the best filter for your AC system. Here’s why we recommend what we do.
What to buy
Standard white pleated filter — MERV 8 to MERV 10
- White pleated polyester media — not fiberglass, not electrostatic, not high-MERV thick filters
- MERV 8 is our minimum — below this a filter does very little to protect the system
- MERV 10 is the upper end for most homes — better filtration without hurting airflow
- Catches dust, pollen, pet dander, and household particles
- Replace on schedule — a dirty pleated filter becomes just as restrictive as a high-MERV filter
- Buy the correct size — measure your filter slot opening, not an old filter that may have shrunk
What to avoid
High-MERV filters — MERV 13 and above
- High-MERV filters catch more particles — but restrict airflow significantly more
- Your system is designed to move a specific volume of air. Too much resistance and airflow drops
- Reduced airflow causes the evaporator coil to freeze, losing all cooling capacity
- On older systems with standard blower motors, high-restriction filters can noticeably reduce CFM
- Thick 4" media filters can be fine — only with the right filter cabinet and system design
- The "better filtration" argument only holds if your system can pull air through it
Understanding MERV: The Industry Standard Rating
When you shop for air filters online or at most hardware stores, you’ll see a MERV rating on the packaging. Here’s what it means and how to use it.
What MERV stands for
MERV stands for Minimum Efficiency Reporting Value. It’s the official industry-standard rating system for air filters, developed by ASHRAE — the American Society of Heating, Refrigerating, and Air-Conditioning Engineers — back in 1987. The scale runs from 1 to 16, with higher numbers indicating a filter that captures smaller particles more effectively.
What MERV measures
MERV ratings measure how effectively a filter captures particles across a range of sizes — from large visible particles like dust and lint all the way down to fine particles like mold spores, pet dander, and some smoke. The testing is standardized and conducted by independent third parties, which is why MERV is recognized across the entire HVAC industry — by manufacturers, contractors, and building engineers worldwide.
| MERV | Airflow impact | What it catches | Best for | Our take |
|---|---|---|---|---|
| 1-4 | Excellent | Large dust and lint only | Nothing useful — "boulder catchers" | Fiberglass panels. Protects equipment from large debris only. Do not use. |
| 6-7 | Very good | Dust, pollen, mold spores | Budget-conscious with no allergies or pets | Minimal. We recommend stepping up to MERV 8. |
| 8 | Good | Dust, pollen, pet dander, mold | Most Las Vegas homes — our minimum | The starting point for real system protection. Our recommendation. |
| 10 | Good | All MERV 8 plus finer dust | Homes with pets, mild allergies, dusty environment | Our preferred range. Better filtration, still safe for most systems. |
| 11-12 | Fair | Fine particles, some smoke | Allergy households — with the right system | Use with caution. Higher static pressure — verify your system can handle it. |
| 13+ | Poor–Fair | Very fine particles, bacteria | Medical-grade needs only | Not for standard residential use. Can restrict airflow and cause coil freeze. |
Understanding FPR: What You See at Home Depot
If you’ve shopped for filters at Home Depot, you may have noticed that their filters don’t always show a MERV rating on the front. Instead they show an FPR number — and it can be confusing when you’re trying to compare.
What FPR stands for
FPR stands for Filter Performance Rating. It’s a rating system created by Home Depot specifically for the filters sold in their stores — including their Honeywell and HDX branded filters. It’s not an industry standard and doesn’t appear on filters sold elsewhere. FPR runs on a scale from 4 to 10, with 10 being the highest filtration level.
How Home Depot grades their filters
Home Depot uses a weighted formula to calculate FPR. The rating factors in how well the filter captures large particles (60% of the score), how well it captures small particles (30% of the score), and how much weight the filter gains over its lifetime as it loads up with debris (10% of the score). FPR filters are also color-coded to make picking one off the shelf faster:
| FPR Rating | Color code | Home Depot label | Best for | Notes |
|---|---|---|---|---|
| FPR 4–5 | Green | Good | Basic dust and lint | Minimum filtration. Fine for very clean homes with no pets or allergies. Not our recommendation for Las Vegas. |
| FPR 6-7 | Red | Better | Households with pets or mild allergies | Moderate filtration. Reasonable airflow. OK for most systems. |
| FPR 8-9 | Purple | Best | Allergy households, better particle control | Good filtration. Check your system can handle the added static pressure. |
| FPR 10 | Black | Premium | High-filtration needs | Highest FPR level. Similar restrictions as high-MERV. Use with caution on standard systems. |
FPR vs MERV — the conversion chart
When you’re standing at Home Depot looking at an FPR-rated filter and trying to figure out what MERV that equals, use this chart. Note that FPR 5 is the one to look for — it equals MERV 8, which is our minimum recommendation.
| MERV Rating | FPR Rating | FPR Color | Our take |
|---|---|---|---|
| MERV 6 | FPR 4 | Green | Below our minimum recommendation — skip this one |
| MERV 8 | FPR 5 | Green | Our minimum — the filter to grab if you want to protect your system |
| MERV 10 | FPR 6-7 | Red | Upper end of our recommended range — good balance of filtration and airflow |
| MERV 11 | FPR 8 | Purple | Use with caution — check your system can handle the added static pressure |
| MERV 12 | FPR 9 | Purple | Higher restriction — not recommended for most standard systems |
| MERV 13 | FPR 10 | Black | Not recommended for standard residential systems |
Shopping at Home Depot? Look for FPR 5 (Green label) for a MERV 8 equivalent — our minimum recommendation. FPR 6 or FPR 7 (Red label) gives you MERV 10 — our preferred range for most Las Vegas homes.
If the filter only shows an FPR number and no MERV rating, use the conversion chart above to find the right one.
One important note about FPR:
FPR is a proprietary rating created by Home Depot — it is not verified by independent third-party testing the way MERV is. That doesn't make it wrong, but it does mean MERV is the more reliable and universally comparable standard. When in doubt, look for a filter that shows its MERV rating directly on the packaging.
Why Airflow Matters as Much as Filtration
Most homeowners assume a higher rating always means a better filter. That’s true for filtration — but not for your HVAC system as a whole.
Every filter creates resistance
To catch smaller particles, a filter needs denser media. Denser media creates more resistance to airflow — measured in inches of water column. Your HVAC system has a total external static pressure budget — essentially the maximum resistance the blower can work against and still move the right amount of air. Most residential systems are designed around 0.5 inches of water column total. A high-MERV filter alone can consume more than half that budget before you account for your ductwork, coils, and grilles.
Low airflow damages your system
When airflow across the evaporator coil drops below what the system needs, the coil gets too cold — below freezing. Moisture in the air freezes on the coil surface, ice builds up, airflow drops further, and the system loses all cooling capacity. A clogged or overly restrictive filter is one of the most common causes of a frozen evaporator coil and is one of the leading contributors to low suction pressure that looks like a refrigerant problem but is actually an airflow problem.
The bottom line:
A MERV 8 to MERV 10 pleated filter changed on schedule protects your system better than a MERV 13 filter that restricts airflow or stays in too long. Both filtration and airflow matter. Choose a filter that respects both.
When to Change Your Filter in Las Vegas
Las Vegas is a high-particulate environment. Desert dust, construction, and long AC runtimes mean your filter loads up faster here than most places.
Our schedule for Las Vegas:
Summer — June through September: Every 30 days.
Your system runs nearly continuously. More runtime means more air through the filter and faster loading. A filter that's fine in October can be clogged solid by mid-July.
Off-season — October through May: Every 60–90 days.
The system runs less. Check it at 60 days — if it looks grey and loaded, replace it. If it's still relatively clean, another 30 days is fine.
Quick visual check
| Check | What it means |
|---|---|
| Hold to light | Can't see light through the media → replace. A new white pleated filter is translucent. A clogged one is solid grey or brown. |
| Check color | White or light grey = still has life. Dark grey, brown, or black = replace now. |
| Feel airflow | Noticeably weaker airflow from a supply vent than usual → check the filter before calling for service. |
| Electric Bill | An unexplained jump in your power bill in summer is sometimes a sign the blower is working harder against a clogged filter. |
How to Find the Right Filter Size
Before you buy, you need the correct size. Filter sizes are printed on the side of your existing filter in Length × Width × Depth format — for example 16×25×1 or 20×20×4. The depth matters — a 1″ slot cannot accept a 4″ filter.
To find your size:
- Check the cardboard frame of your existing filter — dimensions are printed on the side
- Measure the filter slot opening if the filter has been removed or the label is unclear
- If you have multiple return grilles, check each one — some homes use different sizes
- Use the slot size, not the labeled filter size — manufactured filters run slightly smaller than nominal
What We Check at Every Maintenance Visit
Every Orange Air maintenance visit includes a filter inspection. We’ll tell you the condition of your existing filter and recommend what to buy before the next visit.
- Filter condition — visual inspection, MERV or FPR rating, and how loaded it is
- Airflow check — restricted airflow patterns that indicate the filter has been hurting system performance
- Filter size confirmation — if you're unsure what to buy, we note the exact dimensions
- Coil inspection — a long-running dirty filter often leaves deposits on the evaporator coil, which we clean if needed
Frequently Asked Questions
What's the difference between MERV and FPR?
MERV (Minimum Efficiency Reporting Value) is the official industry-wide standard used by HVAC manufacturers, contractors, and engineers. It's independently tested and recognized everywhere. FPR (Filter Performance Rating) is a system created by Home Depot for filters sold in their stores. It's not independently verified the same way MERV is, but it gives you a useful way to compare filters within their product line. When buying at Home Depot, FPR 5 equals roughly MERV 8 and FPR 6-7 equals roughly MERV 10 — our recommended range.
Why does Home Depot use FPR instead of MERV?
Home Depot created FPR to make filter shopping simpler for consumers in their stores. Their color-coded system — green, red, purple, black — is easy to read off the shelf without doing any research. The tradeoff is that it's proprietary and harder to compare against filters sold elsewhere. If a filter shows both an FPR and a MERV number on the label, use the MERV number to compare against other brands.
Can I use a MERV 13 filter for better air quality?
You can, but we don't recommend it for most standard residential systems. MERV 13 restricts airflow significantly more than MERV 8 or 10. If your system wasn't designed for that level of static pressure, you'll get reduced airflow — which can lead to a frozen evaporator coil over time. If indoor air quality is a high priority, talk to us about whether your system can support a higher-MERV filter or whether a separate air purification solution makes more sense.
What about thick 4" or 5" media filters?
Thick media filters can work well — but only if your system has the right filter cabinet for them. A large surface area keeps static pressure low even at higher MERV ratings. If your system was designed for a 1" filter, a 4" filter in an adapter may not give you the benefit you expect. Ask us at your next visit whether your system is a good candidate.
Does it matter which direction the filter goes in?
Yes. The arrow on the filter frame shows the direction of airflow — it should point toward the air handler or furnace, away from the return. Installing it backward reduces its effectiveness and can cause it to collapse into the blower over time.
My system has two return grilles. Do I need a filter at both?
If both returns connect to the same air handler, there should be a filter at each one. Unfiltered air through any return means dust reaches the evaporator coil directly. Let us know at your next visit if you're unsure.