The MrCool DIY 4th Gen outperforms the 3rd Gen in every measurable category: 10% higher efficiency (22 vs 20 SEER2 for the 12K model), 9°F colder heating capability (-4°F vs 5°F), 2 dB quieter indoor operation, and improved build quality. The 4th Gen costs $200–$300 more per unit. For most buyers, the 4th Gen is worth the premium — but the 3rd Gen remains a solid value if you find it discounted.
5th Gen is the current generation. MrCool now sells a 5th Gen DIY line that is the current production model — 23.5 SEER2 with R-454B refrigerant (low-GWP, A2L, compliant with the EPA AIM Act manufacturing cutoff), cold-climate certified. Per locked-spec data, the 4th Gen runs R-410A (legacy refrigerant, manufacturer cutoff Jan 1, 2025) — pre-2025 inventory may still be installed in most states (EPA amended final rule, effective Jul 27, 2026), but the 4th Gen is no longer the current line. This comparison covers 3rd vs 4th Gen because both remain in distribution; if you're buying new in 2026, evaluate the 5th Gen too. Source: MrCool manufacturer pages (mrcool.com).
Head-to-Head Specification Comparison
12,000 BTU Models
| Spec | 3rd Gen (DIY-12-HP-230B) | 4th Gen (DIY-12-HP-230C) | Difference |
|---|---|---|---|
| SEER2 | 20.0 | 22.0 | +10% efficiency |
| HSPF2 | 9.0 | 10.0 | +11% heating efficiency |
| EER2 | 11.0 | 12.0 | +9% peak efficiency |
| Indoor noise (low) | 27 dB | 25 dB | 2 dB quieter |
| Indoor noise (high) | 48 dB | 46 dB | 2 dB quieter |
| Outdoor noise | 53 dB | 51 dB | 2 dB quieter |
| Min heating temp | 5°F | -4°F | 9°F improvement |
| Heating capacity at 17°F | ~9,000 BTU (75%) | ~10,800 BTU (90%) | +20% at cold temps |
| WiFi | SmartHQ | SmartHQ (improved) | Better app |
| Smart home integration | Google, Alexa | Google, Alexa | Same |
| Refrigerant | R-410A | R-410A | Same |
| Line set connection | Quick-connect | Quick-connect (improved seals) | Better reliability |
| Compressor warranty | 7 years | 7 years | Same |
| Equipment price | $900–$1,200 | $1,100–$1,500 | +$200–$300 |
All Available Sizes
| Size | 3rd Gen SEER2 | 4th Gen SEER2 | 3rd Gen Price | 4th Gen Price | Price Difference |
|---|---|---|---|---|---|
| 12K | 20.0 | 22.0 | $900–$1,200 | $1,100–$1,500 | +$200–$300 |
| 18K | 18.0 | 20.0 | $1,100–$1,400 | $1,300–$1,700 | +$200–$300 |
| 24K | 17.5 | 19.0 | $1,300–$1,700 | $1,500–$2,000 | +$200–$300 |
| 36K | 16.5 | 18.0 | $1,600–$2,100 | $1,800–$2,500 | +$200–$400 |
Energy Cost Savings: 4th Gen vs 3rd Gen
The 10% efficiency improvement translates to real electricity savings over the life of the unit:
| Scenario | 3rd Gen Annual Cost | 4th Gen Annual Cost | Annual Savings | 10-Year Savings |
|---|---|---|---|---|
| 12K, moderate climate, $0.17/kWh | $156 | $142 | $14 | $140 |
| 12K, hot climate, $0.17/kWh | $234 | $213 | $21 | $210 |
| 12K, moderate climate, $0.27/kWh (CA) | $248 | $225 | $23 | $230 |
| 18K, hot climate, $0.17/kWh | $351 | $316 | $35 | $350 |
| 24K, hot climate, $0.17/kWh | $468 | $431 | $37 | $370 |
The energy savings alone don't justify the $200–$300 premium over 10 years. The real value is in the improved cold-climate performance, lower noise, and better build quality.
Buy the 4th Gen if: You care about noise (bedrooms, offices), live in a cold climate (the -4°F vs 5°F matters), or plan to keep the unit 10+ years (better build quality = longer life). Buy the 3rd Gen if: You find it heavily discounted ($200+ below 4th Gen pricing), you're installing in a garage or workshop where noise isn't critical, or you're in a warm climate where cold-climate heating doesn't matter.
Key Takeaways
- MrCool DIY 4th Gen beats the 3rd Gen on every spec: SEER2 (22 vs 20), HSPF2 (10 vs 9), min heat temp (-4°F vs 5°F), and indoor noise (25 dB vs 27 dB). Both still use R-410A.
- 5th Gen is the current generation (mrcool.com): 23.5 SEER2, R-454B refrigerant, cold-climate certified — if you're buying new in 2026, evaluate the 5th Gen too. R-410A 4th-Gen inventory may still be installed in most states (EPA amended final rule, effective Jul 27, 2026), but it's no longer the current line.
- Always verify specifications against the AHRI directory for independently certified performance data.
- The federal 25C tax credit (up to $2,000) expired for installs after Dec 31, 2025 under the OBBBA; state and utility rebates plus IRA HEAR / HOMES programs remain the active 2026 federal pathways.