A DG calculator, short for Diesel Generator Calculator, is a digital tool used to determine the appropriate capacity of a diesel generator needed to power a specific load. It takes into account factors such as total running load, starting load, power factor, and startup multipliers to deliver a precise kilowatt (kW) output. This ensures that the generator is neither undersized (leading to overload) nor oversized (leading to inefficiency). It plays a vital role in energy planning for homes, industries, construction sites, and critical facilities.
Detailed Explanations of the Calculator’s Working
The DG calculator functions by analyzing both steady-state and transient electrical demands. It requires inputs such as the total running load in kilowatts (kW), additional starting loads (especially for motors or compressors), the starting factor (based on equipment type), and the system’s power factor. By combining these values, the tool estimates the generator size required to handle startup surges and continuous operation without stress. This approach minimizes errors, avoids system underperformance, and helps comply with safety standards and energy regulations.
Formula with Variables Description
Generator Capacity (kW) = (Total Running Load (kW) + (Starting Load (kW) * Starting Factor)) / Power Factor
- Total Running Load (kW): Continuous load the generator must supply.
- Starting Load (kW): Additional temporary power needed during motor/compressor startup.
- Starting Factor: Multiplier based on equipment type (usually ranges from 2 to 7).
- Power Factor: Typically 0.8 for most generators (accounts for inefficiencies in AC systems).
Reference Table for Common Generator Sizing Estimates
| Application Type | Running Load (kW) | Starting Factor | Suggested DG Size (kW) |
|---|---|---|---|
| Small Office (Basic AC) | 5 | 3 | 25 |
| Medium Factory | 25 | 2.5 | 100 |
| Large Commercial Building | 50 | 2 | 150 |
| Residential House | 3 | 2 | 8 |
| Data Center (Sensitive Load) | 40 | 1.5 | 90 |
Example
Suppose a facility has a total running load of 40 kW and a motor with a starting load of 20 kW. The starting factor is 2.5 and the power factor is 0.8. Applying the formula:
Generator Capacity = (40 + (20 * 2.5)) / 0.8
= (40 + 50) / 0.8
= 90 / 0.8
= 112.5 kW
So, the recommended diesel generator capacity is approximately 113 kW.
Applications
Industrial Backup Systems
Factories and manufacturing plants often run heavy machinery that requires high starting loads. DG calculators ensure backup generators can handle surges without tripping or stalling.
Commercial Installations
Retail centers, hospitals, and corporate offices need uninterrupted power. Proper sizing using a DG calculator ensures continuity during outages, protecting sensitive equipment.
Residential and Emergency Use
For home use, especially in disaster-prone areas, a DG calculator helps homeowners choose the right generator capacity for appliances, HVAC systems, and emergency lighting.
Most Common FAQs
The power factor accounts for the efficiency with which electrical power is converted into useful work. Since most generators operate at a power factor of 0.8, ignoring this can lead to underestimating the generator size, resulting in overloads and reduced lifespan.
Yes, although it is designed for diesel generators, the basic principles of load estimation apply to petrol and gas generators. However, always adjust for fuel type-specific performance and load-handling characteristics.
Oversizing results in higher fuel consumption, unnecessary capital expenditure, and reduced efficiency. Generators operating at low loads frequently can suffer from “wet stacking,” leading to soot build-up and performance issues.
Starting factors vary by equipment type. Motors typically range from 2 to 7. Consult the manufacturer’s specifications or use standardized charts available in electrical design manuals for accurate inputs.