Monocrystalline 400W vs Bifacial Monocrystalline 420W — Solar Panel Comparison
Compare Monocrystalline 400W (20.5% efficiency) vs Bifacial Monocrystalline 420W (21.3% efficiency). Side-by-side cost, payback, output, and specs.
Usage & location
Find on your electricity bill
Panel & battery
15
Panels needed
5.9 kW
System size
$12,390
Net cost (after ITC)
3.7 yrs
Payback period
100% offset$3,321/yr savings5.8 sun hrs/day9,340 lbs CO₂/yr offset
| Monthly usage | 900 kWh |
| Annual usage | 10,800 kWh |
| Peak sun hrs/day | 5.8 hrs |
| System size | 5.93 kW-DC |
| Panels needed | 15 |
| Panel area total | 323 sq ft |
| Annual production | 10,924 kWh |
| Offset | 100% |
| CO₂ offset | 9,340 lbs/yr |
| Equivalent trees | 195 trees/yr |
Monocrystalline 400W vs Bifacial Monocrystalline 420W — head to head
Specifications from manufacturer datasheets.
Cost & payback comparison (900 kWh/month, CA)
Comparison using 900 kWh/month in California (5.8 sun hrs/day).
Efficiency comparison
STC rated efficiency.
Payback period by state (900 kWh/month)
Monocrystalline 400W — payback varies significantly by state electricity rate and sun hours.
Which panel is better?
Bifacial Monocrystalline 420W wins on efficiency (21.3% vs 20.5%) — fewer panels needed for the same output.
Monocrystalline 400W is less expensive (net $12,390 vs $14,994 in CA).
For limited roof space, choose the higher-efficiency panel. For larger roofs where cost matters more, the lower-cost panel offers better value.
Sources & Standards
- Dobos, A. P. "PVWatts Version 5 Manual." National Renewable Energy Laboratory, NREL/TP-6A20-62641, 2014.PV system output estimation methodology (irradiance, system losses, tilt and azimuth)
- National Renewable Energy Laboratory. "National Solar Radiation Database (NSRDB)."Solar irradiance data underlying production estimates