Formula Used
Steady load: Running watts + future watts
Surge load: Running watts + largest starting watts + other surge watts + future watts
Required watts: Surge load × (1 + reserve percent ÷ 100)
Derated generator rating: Required watts ÷ usable factor
Usable factor: 1 - total derating percent ÷ 100
Recommended kVA: Recommended watts ÷ power factor ÷ 1000
Runtime: Fuel tank liters ÷ fuel use liters per hour
Single phase current: VA ÷ voltage
Three phase current: VA ÷ (√3 × voltage)
How to Use This Calculator
Enter the steady running watts for all connected loads. Add the highest starting load from motors, pumps, compressors, or refrigerators. Include other surge loads when multiple devices may start together. Add reserve margin for safety. Enter site altitude, temperature, fuel data, voltage, and phase type. Press the calculate button to view the result above the form.
Example Data Table
| Load Item |
Running Watts |
Starting Watts |
Notes |
| Refrigerator |
700 |
2200 |
Motor surge included |
| Lights |
500 |
0 |
Resistive load |
| Water pump |
1200 |
3000 |
Use largest start value |
| Tools |
1100 |
500 |
Intermittent load |
Power Suite Generator Planning
A power suite generator calculator helps you match supply to real load. It studies running watts, starting surge, power factor, reserve margin, and site derating. These values matter because a generator rarely works in perfect conditions. Motors, pumps, compressors, and tools can demand much more power during startup. Heat and altitude can also reduce available output.
Why Generator Sizing Matters
A small generator may trip, stall, or damage connected equipment. A large generator can waste fuel and run below an efficient load range. Good sizing finds a balanced rating. It gives enough surge support without buying too much capacity. The method also helps compare continuous demand with short peak demand. That makes planning safer for homes, workshops, events, farms, and mobile work sites.
Important Inputs
Running watts describe the steady load after equipment is operating. Starting watts describe the short surge needed by inductive devices. Power factor converts real power into apparent power. Reserve margin gives space for future loads and measurement error. Derating adjusts the result for altitude and temperature. Runtime estimates fuel planning from tank size and hourly consumption.
Physics Behind The Result
The calculator uses power relations used in electrical physics. Real power is measured in watts. Apparent power is measured in volt amperes. The generator must handle the larger requirement after surge and derating. When power factor is lower, apparent demand rises. When derating is higher, the selected generator rating must increase.
Practical Use
List each appliance before using the form. Add nameplate values when available. Use measured wattage for better accuracy. Put the highest single motor surge into the largest surge field. Add reserve for uncertain loads. Review the load percentage to avoid constant overload. The result is a planning estimate. Always check local codes, transfer switch rules, and manufacturer data before installation.
Reading The Output
Recommended watts show the minimum corrected rating. Recommended kilovolt amperes help when labels use apparent power. Surge headroom shows extra startup space. Fuel runtime gives a basic operating estimate. The status note explains whether the chosen generator looks undersized, balanced, or oversized. Use that note with judgment, not as a final engineering approval. Update loads whenever tools, appliances, or site conditions change during each season.
FAQs
What is a power suite generator calculator?
It estimates generator size using running load, surge load, power factor, reserve margin, derating, and fuel runtime. It helps compare demand against a selected generator rating.
Why are starting watts important?
Motors and compressors may need much higher power during startup. Ignoring starting watts can make a generator stall, trip, or fail to start connected equipment.
What does power factor mean?
Power factor compares real power with apparent power. Lower power factor increases kVA demand, so the generator may need a larger apparent power rating.
Why does altitude reduce generator output?
Higher altitude reduces air density. Engines may receive less oxygen, so combustion and output can drop. The calculator applies a basic altitude derating estimate.
Why does temperature matter?
High temperature can reduce engine and alternator performance. It may also affect cooling. The calculator adds a simple temperature derating allowance.
What reserve margin should I use?
A reserve margin of 15% to 25% is common for planning. Use more when loads are uncertain, motors are heavy, or future equipment may be added.
Can this calculator replace an electrician?
No. It is a planning tool. Use it before discussing final wiring, transfer switches, grounding, breaker ratings, and local rules with a qualified professional.
What is a good load percentage?
Many generators work best when not constantly overloaded. A moderate running load with surge headroom is usually better than operating near the limit.