Generator + Hybrid Inverter Integration: Expert Guide 2026

Integrating a genset with a hybrid inverter is the ultimate solution for guaranteeing a 100% reliable power supply, even in the event of a prolonged power cut. This technical guide is aimed at professional installers and informed private individuals who want to master the subtleties of sizing, wiring, frequency stabilisation and preventive maintenance of a hybrid solar installation with genset backup.

Unlike a simple grid connection, interfacing with a genset requires an in-depth understanding of mechanical regulation (engine speed), electrical regulation (AVR/Inverter) and inverter synchronisation protocols. An error in sizing or parameter setting can lead to connection refusals, untimely shutdowns, or even damage to the equipment.

🔧 Section 1: Engineering sizing of the generating set

1.1 Rigorous sizing formula

Sizing a genset to supply a hybrid inverter follows a precise formula:

With :

• _Battery load (W) = Load current × Battery voltage
  Example: 80A × 48V = 3840 W
• Pbypass_consumers (W) = Power of priority loads supplied directly
  Example: 3000 W (lighting, fridge, pump)
• _Ksafety = 1.35 (empirical safety coefficient)

1.2 Explanation of the 1.35 coefficient

⚠️ CRITICAL WARNING: The 1.35 factor is NOT an arithmetic product of cos φ (load power factor). It is an empirical operational safety coefficient that covers :

Why 1.35 and not cos φ?

• ❌ C ommon error: Applying a cos φ = 0.8 to all loads → unnecessary oversizing.
• ✅ Technical reality:
  • Resistive loads (radiators, hot water tanks): cos φ = 1.0 (no derating).
  • Hybrid inverters on battery load: cos φ ≈ 0.95-0.98 (quasi-unity)
  • Inductive loads (motors, pumps): cos φ = 0.7-0.85 (specific derating)
• ✅ Conclusion: The 1.35 is an overall operational safety margin, not a simple product of power factors.

1.3 Example of a Rigorous Calculation

Detailed calculation:

1. Pcharge_battery = 80A × 48V = 3840 W
2. _Pbypass = 3000 W
3. _{Total active power} = 3840 + 3000 = 6840 W
4. Pgroup_required = 6840 × 1.35 = 9234 VA ≈ 10 kVA

✅ Recommended generator set: 10-12 kVA diesel 1500 RPM

1.4 Quick Sizing Table

⚡ Section 2: Choice of Generator Type

2.1 Comparison 1500 RPM vs 3000 RPM

✅ Professional recommendation: For integration with a hybrid inverter and regular use (>10 hours/month), give preference to a 1500 RPM diesel genset. The initial extra cost (×2) is amortised in 2-3 years thanks to its durability and energy efficiency.

2.2 Type of control: AVR vs Inverter

⚠️ CAUTION INVERTER GENERATORS: Although theoretically superior in terms of stability, some Inverter generators generate parasitic harmonics that are incompatible with the synchronisation of hybrid inverters. Solution: Insert a resistive buffer load (1000-2000W) between the genset and the inverter to "smooth" the waveform.

🔌 Section 3: Wiring and Electrical Protection

3.1 Connection Architecture by Inverter Brand

⚠️ SOFAR HYD ABSOLUTE RULE: Before any connection of a genset, you MUST disable the Grid Feed function in the inverter menu. Major risk: Power injection into the genset → destruction of the genset AVR and the inverter output stage.

3.2 AC Cable Section (Group → Inverter)

⚡ Battery wiring → inverter: To connect Pylontech US5000 batteries to the inverter, use 2×25mm² cables to minimise ohmic losses :

3.3 Neutral and earthing system

Mandatory configuration :

• ✅ Generator set: Chassis ground → Local earth (30Ω max post) + Isolated neutral (no N-PE bridging on the set)
• ✅ Hybrid inverter: Earth connected to general building earth (equipotential)
• ✅ Type A 30mA differential upstream of the inverter (mandatory for personal safety)
• ❌ NEVER bridge neutral and earth on the generator side (risk of untimely differential tripping)

🎛️ Section 4: Hybrid Inverter settings

4.1 Deye SUN-xK-SG parameters (via LCD screen or Solarman)

📖 Official documentation: Refer to the Deye UPS with Pylontech batteries Commissioning Guide for detailed procedures.

4.2 WKS / Voltronic parameters (via LCD or WatchPower)

⚠️ WKS specificity: The integrated dry relay has 3 contacts(NO / Common / NC) enabling direct control of the genset start (connection to starter contactor or genset auto-start terminal block).

🔄 Section 5: Frequency Stabilisation Procedure

5.1 Synchronisation issues

Modern hybrid inverters require an extremely stable frequency (±0.5 Hz around 50.0 Hz) to accept connection. However, a generator set at no load or under load has a fluctuating frequency (48-52 Hz) due to :

• ⚙️ Mechanical inertia: Unstable engine speed at low load.
• ⚡ A VR regulation: Response time 100-300ms → transient oscillations.
• 🔥 Engine temperature: Variable speed during warm-up phase

5.2 "Ghost Load" technique

Principle: Connect a pure resistive load (radiator, resistive ballast) directly to the genset BEFORE connection to the inverter to mechanically stabilise the motor.

Phantom load sizing :

• ✅ Group 5-8 kVA → 1000-1500W
• ✅ Group 8-12 kVA → 1500-2500W
• ✅ Group 12-20 kVA → 3000-5000W

5.3 Progressive rise in load current

⚡ FIELD PROCEDURE (Deye SUN-xK-SG):

1. Step 1: Start generator at no load → Wait 3-5 min (temperature rise).
2. Step 2: Set Gen Charge Current = 10A → Connect inverter
3. Step 3: Check inverter display: "GEN Connected" + "50.0 Hz" + "230V".
4. Step 4: Gradually increase current: +10A every 2 minutes
   • 10A → 20A → 30A → 40A → 50A → 60A → 80A (max)
5. Step 5: Monitor voltage/frequency at each level:
   • ✅ Voltage: 220-240V stable
   • ✅ Frequency: 49.5-50.5 Hz stable

⚠️ If frequency unstable (>±1 Hz): Reduce load current by 20A and keep phantom load connected.

🛠️ Section 6: Physical Installation and Nuisances

6.1 Ideal Location of the Generator

6.2 Noise Reduction

Additional solutions:

• 🔇 So undproof enclosure: -10 to -15 dB(A) (mandatory in residential areas)
• 🔇 Anti-vibration blocks: -5 dB(A) (ground vibration reduction)
• 🔇 Reinforced exhaust silencer: -8 dB(A)
• 🔇 Acoustic screen (wall, dense hedge) : -5 dB(A)
• ⏱️ Timetable: 8am-8pm operation only (neighbourhood-friendly)

🔧 Section 7: FIELD DIAGNOSTICS AND TROUBLESHOOTING (ULTRA-EXHAUSTIVE)

This section provides a comprehensive troubleshooting guide to quickly identify and resolve common generator/hybrid inverter integration problems. Each symptom is analysed with its probable causes, diagnostic tests and costed solutions.

7.1 Systematic Diagnostic Methodology (5 steps)

7.2 PROBLEM #1: Abnormal Genset Smoke

"A black-smoking genset consumes 15-25% more fuel and loses 10-20% power. Cleaning the air filter and injectors immediately improves performance."
- Michel Dubois, authorised ITC Power Belgium technician

7.3 PROBLEM #2: Impossible or difficult to start

🌳 DIAGNOSTIC DECISION TREE (follow in order):

STEP 2: Electrical diagnosis (starter does not turn).

STEP 3: Mechanical/Fuel Diagnosis (starter runs, engine won't start)

⚙️ DIESEL CIRCUIT PURGE PROCEDURE (air in circuit) :

1. Locate fuel filter bleed screw (usually on top of filter)
2. Fill diesel tank (minimum 10 litres)
3. Open fuel tap
4. Slightly unscrew bleed screw (1-2 turns)
5. Operate manual pump (if present) or starter by jerking for 5 sec.
6. Wait for diesel to flow without bubbles (30-60 sec)
7. Tighten bleed screw firmly
8. Test start

7.4 PROBLEM #3: Voltage Unstable or Out of Tolerance

7.5 PROBLEM #4: Frequency Unstable or Out of Range

🔧 ENGINE IDLE RATE ADJUSTMENT (adjusting screw access) :

1. Locate idle stop screw (usually on carburettor or injection pump).
2. Start no-load generator → stabilise for 5 min
3. Measure multimeter frequency (Hz mode)
4. If frequency <49 Hz : Turn stop screw clockwise 1/4 turn → increase idle speed
5. If frequency >51 Hz : Unscrew stop 1/4 turn anticlockwise → reduce idle speed
6. Wait 30 sec for stabilisation between each adjustment
7. Target: 50.0 Hz ±0.3 Hz at no load
8. Then test with 30% load → frequency must remain 49.5-50.5 Hz

7.6 PROBLEM #5: Inverter Connection Refusal (Error Codes)

📟 DEYE UPS ERROR CODES (SUN-xK-SG series) :

🔧 CHECKLIST QUICK TROUBLESHOOTING (connection refusal) :

7.7 PROBLEM #6: Generator overheating

7.8 PROBLEM #7: Excessive Fuel Consumption

📊 MEASUREMENT METHOD CONSUMPTION (field):

1. Fill the tank to the brim (visual mark).
2. Note the hour meter index (or stopwatch)
3. Run the generator for 2-4 hours with a known load (e.g. constant 3 kW)
4. Stop → Fill tank to brim with graduated jerry can
5. Calculate: Consumption (L/kWh) = Volume added (L) ÷ [Power (kW) × Time (h)]
6. Example: 4L added after 2h at 3kW → 4 ÷ (3×2) = 0.67 L/kWh → ⚠️ abnormal, maintenance required

"A well-maintained unit (clean filters, regulated injection) consumes 15-20% less fuel than a neglected unit. Preventive maintenance pays for itself in 6-12 months of regular use."
- Sophie Lemaire, Kompak Belgium technical trainer

🛡️ Section 8: Rigorous preventive maintenance

8.1 Interval Maintenance Planning

8.2 Long-term storage (>3 months without use)

⚠️ IMPERATIVE PROCEDURE (to avoid damage to diesel + battery) :

1. Option A - Complete draining:
   • ✅ Drain fuel tank (manual pump)
   • ✅ Run engine until stopped due to lack of fuel (empty circuit)
   • ✅ Store drained diesel in opaque jerry can (6 months max)
   • ✅ Advantages: No risk of fuel degradation
   • ❌ Disadvantages: Time-consuming re-commissioning (filling + air purge).
2. Option B - Fuel stabilisation:
   • ✅ Fill tank to 95% (limit condensation).
   • ✅ Add stabilising additive + biocide (e.g. Liqui Moly Diesel Protect, €15-25 / 300mL for 75L)
   • ✅ Run for 10 mins to diffuse additive
   • ✅ Advantages: Immediate restart possible
   • ⚠️ Disadvantages : Diesel usable 12-18 months max (then oil change compulsory)
3. Engine oil change:
   • ✅ Change oil even if <200h (oil in contact with air oxidises)
   • ✅ Fill with new oil (avoids internal corrosion)
4. Starter battery:
   • ✅ Disconnect negative (-) terminal (prevents slow discharge)
   • ✅ Recharge to 100% before storage
   • ✅ Recharge every 3 months (to maintain battery health)
   • ⚠️ If battery >4 years old: consider preventive replacement (€40-80)
5. Mechanical protection:
   • ✅ Complete exterior cleaning (degreaser + water)
   • ✅ Dry thoroughly (compressed air)
   • ✅ Spray WD-40 or CRC on exposed metal parts
   • ✅ Cover with breathable tarpaulin (not waterproof plastic → condensation)
   • ✅ Raise 10-15cm (pallets) to avoid ground humidity

🔄 PUT BACK INTO SERVICE AFTER STORAGE :

1. Reconnect battery → Check charge (>12.5V)
2. Check oil level (top up if necessary)
3. If Option A (fuel change): Fill tank + bleed air from circuit
4. If Option B (stabilisation) : Check diesel age (if >18 months → drain)
5. No-load start test → Allow to warm up for 5-10 min
6. Connect progressive load (1kW → 3kW → nominal)
7. Monitor temperature, oil pressure, smoke
8. If normal operation 30 min → Ready for inverter connection

8.3 Recommended spare parts in stock

For maximum autonomy in the event of a breakdown, keep in stock:

💰Spare parts stock budget: 150-300 € (5-12 kVA group) - Immediate ROI in the event of a breakdown (avoids technician travel 80-150 €).

💰 Section 9: Economic analysis OPEX (Operating Cost)

9.1 Cost per kWh Produced (Detail by Item)

9.2 Group vs Grid vs Battery Only Economic Comparison.

📊 Scenario: Mains outage 4h during winter (consumption 3 kW continuous)

✅ ECONOMIC CONCLUSION:

• Short term (<4h): Battery only = optimal solution (cost + comfort)
• Medium term (4-12h): Hybrid battery + 1500 RPM diesel generator = best compromise
• Long term (>12h or frequent power cuts): 1500 RPM diesel generator essential
• Resilience: invaluable in the event of long power cuts (storms, regional power cuts)

"The genset is not an economic competitor to the grid, it's an insurance policy for energy autonomy. Its ROI is measured in peace of mind and business continuity, not just in euros/kWh."
- Jean-Marc Lejeune, Wattuneed Technical Director

❓ Section 10 : In-depth FAQ (20 Field Questions)