Choosing the right diesel generator size for your Tuis means the difference between powering everything comfortably and having a generator that trips breakers or wastes fuel. The most common mistake homeowners make is buying a generator based on square footage or “what the neighbor has” instead of calculating actual electrical load.
This guide provides a step-by-step method to calculate your home’s power requirements, understand starting vs running wattage, and select the optimal diesel generator size.
Stap 1: List Every Appliance You Need to Power
Not everything needs to run during an outage. Separate appliances into three tiers:
| Vlak | Beskrywing | Tipiese vrag |
|---|---|---|
| Vlak 1: Noodsaaklik | Yskas, freezer, put pomp, sump pump, furnace blower, mediese toerusting, ligte, router/modem | 3-5 KW |
| Vlak 2: Comfort | Vlak 1 + window AC or one central AC unit, water heater, mikrogolf, washer, TV, rekenaars | 7-12 KW |
| Vlak 3: Full Home | Everything including central AC, electric oven, electric dryer, pool pump, EV charger | 15-30+ KW |
Stap 2: Calculate Running and Starting Wattage
Every motor-driven appliance (yskas, AC, put pomp, furnace blower) draws 3-7× its running wattage for 1-3 seconds at startup. This starting surge (inrush current) must be covered by the generator’s surge rating.
| Toestel | Hardloop Watts | Begin Watts |
|---|---|---|
| Refrigerator/freezer (21 cu ft) | 700 | 2,200 |
| Chest freezer (15 cu ft) | 500 | 1,500 |
| Sentrale AC (3 ton, 14 SEER) | 3,500 | 6,000-8,000 |
| Venster AC (12,000 BTU) | 1,200 | 3,600 |
| Well pump (1 HP, 230V) | 1,500 | 4,500 |
| Sump pump (1/2 HP) | 800 | 2,400 |
| Furnace blower (1/2 HP) | 800 | 2,400 |
| Electric water heater (4,500W) | 4,500 | 4,500 (resistive) |
| Microwave | 1,200 | 1,200 |
| LED ligte (10 bulbs) | 100 | 100 |
| TV + router + modem | 300 | 300 |
| Electric oven (single element) | 2,500 | 2,500 (resistive) |
| Clothes washer | 500 | 1,500 |
| Electric dryer | 5,500 | 5,500 (resistive) |
Stap 3: Apply the Load Calculation
Formule: Generator KW = (Total Running Watts + Largest Starting Surge) ÷ 1,000 × 1.25 (veiligheidsfaktor)
Example calculation for a 2,000 sq ft home (Vlak 2):
- Running total: Yskas 700 + Vrieskas 500 + Well pump 1,500 + Furnace blower 800 + AC 3,500 + Ligte 100 + Electronics 300 + Microwave 1,200 = 8,600 watt
- Largest starting surge: AC compressor = 7,000 watt (during the 2 seconds the AC starts, everything else is running)
- Total surge requirement: 8,600 + 7,000 = 15,600 watt
- Met 25% veiligheidsfaktor: 15,600 × 1.25 = 19,500 watts → 20 KW generator minimum
Recommended Diesel Generator Sizes by Home Type
| Home Type | Typical Size | Aanbevole kragopwekker | Estimated Fuel (24h @ 75% laai) |
|---|---|---|---|
| Small apartment / tiny home (Vlak 1 only) | 5-8 KW | 8 KW SC Series | 15-20 L diesel |
| Medium home 1,500 vk voet (Vlak 1 + partial comfort) | 10-15 KW | 15 KW YC Series | 30-40 L diesel |
| Large home 2,500 vk voet (Vlak 2, one AC) | 20-25 KW | 20 KW SC or 25 KW YC | 50-65 L diesel |
| Large home 3,000+ vk voet (Vlak 3, dual AC) | 30-50 KW | 30-50 KW SC/YC Series | 70-120 L diesel |
| Estate / farm with outbuildings | 50-100+ KW | 100 KW WC Series | 150-250 L diesel |
Important Considerations
Single-Phase vs Three-Phase
Most homes in North America use single-phase 120/240V split-phase power. Ensure the generator is configured for single-phase output. Drie-fase Kragopwekkers can be used for homes but require a phase converter or careful load balancing, and you’ll only access 58% of the three-phase rating on single phase.
Continuous vs Standby Rating
Diesel generators have two power ratings: Standby (ESP) for emergency use, tipies 100-200 ure per jaar, and Prime (PRP) for unlimited hours at variable load. For home backup, a standby-rated generator is sufficient and more economical. If you expect multi-day outages regularly, choose a prime-rated unit.
ATS (Outomatiese oordragskakelaar)
A properly sized ATS is essential. It must match the generator’s output amperage. Vir 'n 20 KW single-phase generator at 240V: 20,000 ÷ 240 = 83A. Choose a 100A-rated ATS. The ATS also determines whether you can power the entire house (whole-house switch) or only essential circuits (sub-panel with manual or automatic load shedding).
Brandstofberging
Diesel fuel stores well (6-12 months with stabilizer, 18-24 months in underground tanks), anders as petrol. Calculate storage needs: a 20 KW generator at 75% load consumes approximately 4-5 L/uur. Vir 72 hours of continuous outage: 360L minimum. A 500L day tank provides a comfortable buffer.
Gereelde vrae
V: Can I power my whole house with a 20 KW diesel generator?
A: For most 2,000-2,500 sq ft homes with one central AC, yes—with load management. Without load management, a 20 KW generator may struggle if the AC, electric oven, and dryer all run simultaneously. Adding a load-shedding controller ($300-500) automatically prioritizes essential loads.
V: What happens if my generator is undersized?
A: Voltage and frequency sag under overload. Motor-driven appliances (AC, yskas) burn out from low voltage. The generator’s circuit breaker trips. Repeated overload shortens engine life. In worst case, the generator stalls while connected to the house.
V: Is it better to oversize a home generator?
A: Slightly oversizing (20-30%) is good practice. Severely oversizing causes “nat stapeling”—unburned fuel accumulates in the exhaust system because the engine never reaches operating temperature at very light loads. This reduces efficiency and damages the engine. Aim for 50-80% loading during typical outage conditions.
V: How far from the house should a diesel generator be placed?
A: NFPA 37 requires a minimum of 5 feet from any openings (vensters, deure, vents) en 5 feet from combustible walls unless the wall has a 1-hour fire rating. For noise comfort, 20+ feet is recommended. Check local codes—many municipalities have stricter requirements.
V: Do I need a concrete pad?
A: Ja, a reinforced concrete pad is standard. Minimum 4 inches thick, extending 6 inches beyond the generator base on all sides. For larger units (hierbo 30 KW), 6-inch reinforced concrete is recommended. Pre-cast pads are available for smaller units.
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Recommended Home Backup Generators
- SC Series Diesel Generator Set — 20-80 KW, ideal for home backup
- YC reeks diesel kragopwekkers — 20-250 KW, fuel-efficient
