How Many Solar Panels Do You Need for a Jebel Hybrid Solar AC? Exact Counts by BTU

How to Size Your Jebel Hybrid Solar Air Conditioner (With Exact Panel Counts)

If you’ve chosen a Jebel Hybrid ACDC mono-split (wall-mounted) unit, you already have half the design solved: the outdoor unit contains a built-in MPPT and DC drive that accepts a PV string directly and blends solar with the AC grid as needed during the day. No external solar inverter is required for daytime operation. Batteries are optional if you want night cooling or outage backup.

This post shows you, step by step, how to (1) choose the right AC tonnage for your room and (2) select the exact number of solar panels for each Jebel capacity (9K / 12K / 18K / 24K BTU), while staying inside the PV input limits.

Part 1 — Pick the Right AC Size (Cooling Tons)

A quick, practical approach:

Base cooling load ≈ Room area (m²) × W/m², then adjust for real-world factors.

• Good insulation, little glass: 70–110 W/m²

• Average insulation (typical): 110–150 W/m²

• Hot roof / big glazing / west sun: 150–200+ W/m²

Adjusters

• Large west-facing window: add +10–20%

• More than two people for long periods: +400–600 W per extra person

• Heat-generating appliances/lighting: +10–15%

Convert to tons:
1 ton = 3.517 kW ≈ 12,000 BTU/h

Quick map (after adjustments)

• Up to 15 m² → 0.75 ton (≈9,000 BTU)

• 16–22 m² → 1.0 ton (≈12,000 BTU)

• 23–35 m² → 1.5 ton (≈18,000 BTU)

• 36–45 m² → 2.0 ton (≈24,000 BTU)

Example: 20 m², average insulation, medium west window, two people
→ base 20 × 130 = 2.6 kW; +15% window = 3.0 kW; +0.5 kW people = 3.5 kW
→ ≈1.0 ton (12,000 BTU) (go 1.5 ton if the roof is extremely hot).

Part 2 — Solar Panel Counts for Each Jebel Model

What the Jebel datasheet tells us (the fields we use)

• PV input window (open-circuit voltage): typically 80–380 VDC

  • On some 24K models the minimum PV Voc is 150 VDC

• PV input current limit: typically ≤ 14 A (up to ≤ 20 A on certain high-capacity units)

• Max power input (electrical): the upper bound the unit can draw at full load (used to select a sensible PV kWp)

We size the PV to land near the unit’s max power input (for strong midday solar contribution), keep the string Voc (in cold weather) within the allowed window, and keep string current ≤ input limit. We wire in series first to meet the voltage window; only parallel if you truly need more power while respecting the current limit.

Panel assumptions used in the calculations

• 550 W: Voc ≈ 49 V, Isc ≈ 13 A

• 580 W: Voc ≈ 50 V, Isc ≈ 13 A

• 650 W: Voc ≈ 50–51 V, Isc ≈ 13–14 A

• Cold-weather Voc rise assumed ~+10% (you must check your local minimum temperature and your exact panel datasheet).

Recommended configurations (my calculations)

Why the 24K gets a bit more kWp: rooftop panels run hot at noon, which lowers real output (see temperature effects below). The slight oversize helps cover heat/soiling losses and reduce grid assist during peak hours.

Temperature & Environmental Effects (What Really Happens on the Roof)

• Panel temperature vs. power (Pmax): As the cell temperature rises above 25 °C, panel power typically drops ~0.35–0.45% per °C. Hot rooftops at noon can easily be 30–40 °C above STC, so a -12% to -18% hit is common. This is why a small PV oversize is smart on larger units.

• Panel temperature vs. voltage (Voc): Heat reduces Voc; cold increases it. That’s why we check cold-day Voc to ensure your series string stays below the 380 V limit (or ≥150 V and ≤380 V on models with a higher minimum).

• Soiling (dust): In dusty seasons, uncleaned panels can lose 10–30% of output. A regular cleaning plan materially improves AC solar contribution.

Do You Need Batteries?

• Daytime solar cooling: No battery required. The Jebel hybrid outdoor unit prioritizes PV and blends with the grid automatically when clouds pass.

• Night cooling / backup: Add a compatible LFP battery and hybrid charger/inverter. Roughly size battery energy as:
  Night kWh ≈ (Average AC input kW) × (night hours) × (duty factor), then divide by (DoD × round-trip efficiency) to pick a usable battery capacity.

Quick Checklist (Copy/Paste)

• Room area (m²), insulation class, glazing/solar gain

• Adjusters (people, appliances, west sun)

• Chosen BTU size from the map above

• Panel wattage & datasheet Voc/Isc

• Series string Voc at your coldest day (stay in window)

• String Isc ≤ PV input limit (typically 14 A; up to 20 A on some 24K)

• Cable sizing (voltage drop ≤ 2–3%), DC isolator/fuses, MC4 quality

• Cleaning schedule and app/monitoring set-up

Final Recommendations (Ready to Build)

• 9K BTU: 2 × 650 W in series (alt: 2 × 600 W)

• 12K BTU: 3 × 580 W in series (alt minimum: 2 × 650 W)

• 18K BTU: 4 × 650 W in series (alt: 4 × 580 W)

• 24K BTU: 6 × 650 W in series (alt: 7 × 550 W)

All of the above keep the PV input voltage within the specified window in cold weather and keep string current within the input limit. If your site is extremely dusty or you want more midday solar share, you may add one extra panel to the 18K/24K scenarios—just re-check cold Voc stays below the upper limit.

Frequently Asked Questions

Is the Jebel unit an inverter AC or just “solar-ready”?
It’s a DC-driven hybrid with a built-in MPPT and power electronics in the outdoor unit. You connect PV directly to it and it blends with the grid; no external solar inverter is needed for daytime.

Can I mix panel wattages or brands?
Avoid mixing within the same series string. Keep identical modules together for proper MPPT behavior.

What if my winter Voc is too high?
Reduce the number of modules in series or choose a panel with lower Voc so your cold-day string Voc is inside the limit.

Can I parallel strings for more power?
Only if necessary. Use a combiner/fusing and keep total PV input current ≤ the datasheet limit.