MERV vs HEPA FiltersWhich is Best for Your Home?
HEPA captures 99.97% of particles. MERV 13 captures 50-75%. But HEPA costs 10x more and won't fit your HVAC. Here's what UK homeowners actually need.
Quick Comparison
| Filter Type | Efficiency @ 0.3µm | HVAC Compatible | Typical Cost |
|---|---|---|---|
| HEPA (H13/H14) | 99.97% | ❌ No | £200-800 (purifier) |
| MERV 16 | ~95% | ⚠️ Specialised | £30-50 |
| MERV 13 | 50-75% | ✅ Yes | £15-30 |
| MERV 11 | 35-50% | ✅ Yes | £10-20 |
| MERV 8 | ~20% | ✅ Yes | £5-15 |
H13 HEPA = What MERV Rating?
HEPA and MERV use different rating systems, but they can be compared. Here's the official conversion:
| HEPA Class | Efficiency @ 0.3µm | MERV Equivalent | Typical Use |
|---|---|---|---|
| H14 (Medical HEPA) | 99.995% | MERV 18-20 | Hospitals, cleanrooms |
| H13 (True HEPA) | 99.97% | MERV 17-18 | Air purifiers, medical |
| E12 (EPA filter) | 99.5% | MERV 16-17 | High-end commercial |
| E11 (EPA filter) | 95% | MERV 15-16 | Commercial HVAC |
Key takeaway: When shopping for air purifiers, "H13 HEPA" or "True HEPA" means the filter is equivalent to MERV 17-18. Anything marketed as "HEPA-type" or "HEPA-like" typically falls short of this standard (often MERV 13-15).
🎯 What Does Each Filter Catch?
Particle Size Reference
0.06-0.12 µm: Viruses (including COVID-19)
0.3 µm: Bacteria, combustion smoke
1-3 µm: Lead dust, auto emissions, mold spores
3-10 µm: Dust mite allergens, pet dander
10-100 µm: Pollen, visible dust
100+ µm: Hair, sand, textile fibres
HEPA Catches
- ✓ Viruses (99.97%)
- ✓ Bacteria (99.97%)
- ✓ Fine smoke (99.97%)
- ✓ All allergens (99.97%)
MERV 13 Catches
- ✓ Bacteria (50-75%)
- ✓ Smoke (50-75%)
- ✓ Mold spores (85%+)
- ✓ Pollen & dust (90%+)
MERV 8 Catches
- ✓ Pollen (85%+)
- ✓ Dust mites (65%+)
- △ Mold spores (20%)
- ✗ Fine particles
📊 Efficiency by MERV Rating
| MERV Rating | 0.3-1.0 µm | 1.0-3.0 µm | 3.0-10.0 µm |
|---|---|---|---|
| HEPA (17-20) | ≥99.97% | ≥99.97% | ≥99.97% |
| MERV 16 | ≥95% | ≥95% | ≥95% |
| MERV 14 | ≥75% | ≥90% | ≥95% |
| MERV 13 | ≥50% | ≥85% | ≥90% |
| MERV 11 | ≥35% | ≥80% | ≥90% |
| MERV 8 | ≥20% | ≥65% | ≥85% |
Source: ASHRAE Standard 52.2. Efficiency measured using standardised dust spot test with carbon/cotton particles.
🧮 Real-World Example
If 10,000 particles at 0.3 microns (the hardest size to filter) pass through each filter:
But here's the key: With multiple air changes per hour (ACH), MERV 13 filters the entire room volume 5-6 times per hour. Even at 75% efficiency, after 5 passes you've removed 99.9% of particles. That's why ACH matters as much as filter rating.
💷 Cost Comparison (UK 2026)
HEPA Air Purifier
- Unit cost: £200-800
- Replacement filters: £50-100 each
- Filter life: 6-12 months
- CADR: 150-400 m³/h typical
- Coverage: 20-40m² per unit
Best for: Medical needs, immune-compromised individuals, maximum virus protection
DIY MERV 13 Purifier
- Build cost: £149-200
- Replacement filters: £15-30 each
- Filter life: 3-6 months
- CADR: 600-1,400 m³/h
- Coverage: 60-100m² per unit
Best for: Allergies, hay fever, general air quality, cost-conscious households
5-year cost comparison: HEPA purifier = £600-1,300. DIY MERV = £250-400. MERV delivers 3-4x the CADR at 1/3 the cost.
🎯 Which Filter Should You Choose?
Choose MERV 8-11 if:
- • Standard home/office use
- • General allergen reduction (pollen, dust, pet dander)
- • HVAC compatibility is critical
- • Budget is primary concern
Choose MERV 13 if: ⭐ Recommended
- • Hay fever or allergy sufferers in household
- • Near busy roads or pollution sources
- • Wildfire smoke protection needed
- • Best value for comprehensive air cleaning
Choose HEPA if:
- • Medical facilities, cleanrooms, laboratories
- • Immune-compromised individuals
- • Maximum virus/bacteria protection required
- • Using standalone air purifiers (not HVAC)
🛒 Get Started with MERV Filtration
For most UK homes, MERV 13 delivers excellent air quality at a fraction of HEPA cost. Our DIY kits and pre-built purifiers use 3M Filtrete MERV 13/16 filters with proven performance.
MERV vs HEPA FAQs
What is the difference between MERV and HEPA filters?
HEPA filters capture 99.97% of particles at 0.3 microns (the hardest size to filter). MERV 13 captures 50-75% at the same size. HEPA equals MERV 17-20. The key difference: HEPA needs dedicated air purifiers while MERV 13-16 works in standard HVAC systems.
Is MERV 13 as good as HEPA?
No, but it's good enough for most homes. MERV 13 captures 50-75% of 0.3 micron particles vs HEPA's 99.97%. For allergens (pollen 10-100µm, dust mites 100-300µm), MERV 13 achieves 90%+ capture. HEPA is only necessary for medical-grade filtration or immune-compromised individuals.
Can I use a HEPA filter in my HVAC system?
Usually not. HEPA's dense construction creates high airflow resistance that most residential HVAC systems can't handle without modifications. MERV 13-16 is the practical limit for home HVAC. For HEPA filtration, use dedicated standalone air purifiers.
What MERV rating should I use for allergies?
MERV 11-13 is ideal for allergies. MERV 13 captures 90%+ of pollen (10-100µm), dust mites (100-300µm), and mold spores (3-30µm). This provides excellent allergy relief while remaining compatible with most HVAC systems.
Which is more cost-effective: MERV or HEPA?
MERV is significantly more cost-effective. MERV 13 filters cost £15-30 and fit standard filter slots. HEPA purifiers cost £200-800 for the unit plus £50-100 per replacement filter. DIY Corsi-Rosenthal boxes with MERV 13 filters cost £149-200 and deliver 1000+ CADR.
Related Resources
Health Conditions Hub
Air quality guides for asthma, allergies, COPD & more
Filter Science Explained
How HEPA, MERV & CADR ratings actually work
ACH Calculator
Calculate air changes per hour for your room in 10 seconds
Best Air Purifier for Asthma
NHS-aligned guide to reducing asthma triggers by 60-95%