Mono vs poly solar panel — the short answer
Monocrystalline panels win in 90% of cases. Higher efficiency (21-23% vs 17-19%), more compact, retain output longer, perform better in heat and diffuse light. Polycrystalline costs 10-15% less, but that gap shrinks fast when you account for lower output per square metre.
There are situations where poly still makes sense — temporary installations on a tight budget, or large ground-mount arrays where space is not a constraint. We will break down both types with real numbers.
How mono and poly panels are made
The difference starts at the silicon ingot stage.
- Monocrystalline — silicon is grown using the Czochralski method into a cylindrical ingot with a single crystal lattice. The ingot is then sliced into wafers. The uniform structure means lower resistance to electron flow, hence higher efficiency. Visually — black or dark blue cells, traditionally with clipped corners (now often full-size).
- Polycrystalline — silicon is melted and poured into a square mould where it crystallises randomly, forming many small crystals. Simpler process = cheaper production. Visually — blue cells with a distinctive "frost" pattern.
Mono costs more to produce, but the price gap for finished panels has narrowed from 30-40% in 2018 to 10-15% today.
Specification comparison
| Parameter | Monocrystalline | Polycrystalline |
|---|---|---|
| Efficiency | 21-23% | 17-19% |
| Temperature coefficient | -0.30 to -0.35%/°C | -0.38 to -0.42%/°C |
| Annual degradation | 0.3-0.5% | 0.5-0.7% |
| Output per m² | 195-215 W | 155-175 W |
| Diffuse light performance | Better | Worse |
| Performance warranty | 25-30 years (80-87%) | 20-25 years (80%) |
| Typical wattages | 400-700 W | 250-340 W |
| Price per watt | $0.18-0.24 | $0.15-0.20 |
The 3-5% efficiency gap means poly needs 20-30% more roof area for the same output. On a residential roof where every square metre counts, that is often the deciding factor.
Temperature coefficient — why it matters
In Ukraine, roof surfaces reach 60-70°C in summer. The panel operates at 45-55°C (20-30 degrees above the standard test condition of 25°C).
Calculating losses for a 500 W panel:
- Mono (-0.32%/°C): 500 x 0.32% x 30°C = 48 W loss → real output ~452 W
- Poly (-0.40%/°C): 500 x 0.40% x 30°C = 60 W loss → real output ~440 W
A 12 W difference per panel. Across 20 panels that is 240 W, and over a summer season roughly 36 kWh extra.
Degradation: after 25 years
- Mono: first year -2%, then 0.3-0.5% annually. After 25 years — 85-90% of original output.
- Poly: first year -3%, then 0.5-0.7% annually. After 25 years — 77-83%.
For a 10 kW system that means: mono still generates like 8.5-9 kW after 25 years, poly like 7.7-8.3 kW.
When poly still makes sense
- Temporary installation (under 5 years) — construction sites, temporary cabin power.
- Large ground-mount arrays — where space is unlimited and cost per watt is king.
- Budget under 20,000 UAH — if you need something now and cannot stretch to mono.
But finding new polycrystalline panels on the market is getting harder. Major manufacturers (JA Solar, Longi, Trina Solar, Canadian Solar) have almost entirely switched to mono. What is still sold as "poly" is mostly old stock.
Our recommendation
Monocrystalline 500 W panels with TOPCon technology — for residential use this is the best balance of price, output, and longevity. Browse models in our solar panel catalog.
For an off-grid capable system, add a hybrid inverter and LiFePO4 battery. Not sure about sizing? First calculate how many panels you need.
Frequently Asked Questions
Is it true that poly works better in cloudy weather?
No, that is a myth. Tests show mono generates 5-8% more in diffuse light than poly of the same wattage. The uniform crystal structure converts weak light more effectively.
What is the lifespan difference?
Both types last 25-35 years. But mono retains 85-90% output after 25 years, while poly retains 77-83%.
Can I mix mono and poly panels?
Technically yes, but it is not advisable. Different characteristics in one string drag performance down to the weakest panel. Put mono on a separate string or MPPT input.
Why are poly panels cheaper?
Simpler production: silicon is poured into a mould and crystallises randomly. No Czochralski crystal-growing step, which takes more time and energy.
Is HJT worth the premium over standard mono?
HJT delivers up to 25% efficiency and the lowest temperature coefficient. The 20-30% premium makes sense for large systems (10+ kW) and hot climates. For a standard 5 kW home system, TOPCon is a more balanced choice.
