Generator Sizing Calculator
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Generator Sizing Calculator
Find the right generator for your power needs with our quick, practical tools. Start by working out your total electrical load, then convert that figure into the generator capacity you’ll need. You can also estimate fuel consumption and runtime to plan more efficiently.
Use the calculators below to accurately size your generator, determine the required power, and estimate its runtime under various conditions.
Load Calculator
Enter running watts, starting watts, and quantity. The result includes a built-in 20% safety margin for the recommended generator size.
| Running Watts | Starting Watts | Quantity | Remove |
|---|---|---|---|
Peak Starting Load: -- W
Recommended Generator Size: -- kW (includes 20% margin)
Approx. kVA (at 0.80 PF): -- kVA
kW ↔ kVA Converter
Convert between kW and kVA using power factor. Default PF is 0.8.
Fuel Consumption Calculator
Estimate how much fuel your generator will use per hour at different load levels.
Runtime Calculator
Estimate how long your generator can run before refuelling based on fuel tank size and operating load.
How to Use These Calculators to Choose the Right Generator
Selecting the right generator size is about balancing power demand, efficiency, and fuel use. The four calculators above work together to give you an accurate recommendation and help you plan real-world performance.
Work Out Your Total Load
Start with the Load Calculator to find the combined running and starting wattage of everything you need to power.
If your setup includes items like fridges, pumps, or compressors, remember these draw extra current when starting.
Tip: Add roughly 20% headroom to your total to allow for future equipment or unexpected peaks. The result gives you your total required power in kW.
Convert kW to kVA
Generators are rated in kVA, not kW.
Use the kW ↔ kVA Converter to turn your total load into the generator capacity you need.
Typical power factor (PF) = 0.8
Example:
40 kW÷0.8=50 kVA40\,kW \div 0.8 = 50\,kVA40kW÷0.8=50kVA
That means you’ll need at least a 50 kVA generator to handle the load safely.
Tip: Always round up to the next available generator size to avoid overloading during peak demand.
Estimate Fuel Consumption
Once you know the generator size, use the Fuel Consumption Calculator to see how much fuel it will use at different loads (25%, 50%, 75%, and 100%).
This helps you budget running costs and compare models.
Tip: Generators operate most efficiently between 50–80% load. If your typical use is far below that range, a smaller generator may be more economical.
Check Runtime
The Runtime Calculator estimates how long your generator can operate before refuelling.
Enter your tank capacity and fuel usage from the previous step to see the expected runtime at different loads.
Tip: Short runtime? Choose a larger tank or consider a more efficient generator model.
Step | Tool | Output | Why It Matters |
1 | Load Calculator | Total kW | Your power demand |
2 | kW ↔ kVA Converter | Generator capacity | Matches generator rating |
3 | Fuel Consumption Calculator | Litres per hour | Helps estimate running cost |
4 | Runtime Calculator | Operating hours | Checks tank suitability |
Before You Finalise Your Generator Choice
These calculators are designed to give a reliable estimate based on typical power factors and usage patterns, but real-world requirements can vary. Factors such as motor starting currents, altitude, ambient temperature, and load type can all affect generator performance.
For precise sizing and professional advice, it’s always best to speak with a specialist.
At Canning Generator Solutions, our team can assess your exact power needs and recommend the right generator for your site or application.
WHY CHOOSE US?
Why Choose Canning Generator Solutions?
In short, we get the job done. When power generation and energy management are neglected, the consequences can be disastrous. It’s critical to have a team that responds proactively to potential issues, and our personal, tight-knit values means you can expect exactly that.
Tailored Services
Every client and project is different, so we prioritise clear communication to develop a rich understanding of each client’s needs.
Responsive
When our services are needed, every second counts. That’s why we guarantee a four-hour response to our clients nationwide, bolstered by our dedicated team of service engineers operating 24/7.
Proactive
While our industry often reacts to emergencies, our ethos is to anticipate and mitigate issues before they escalate. We like to get involved early to better plan and optimise your power.
Honest
The relationships we build with clients are hugely important to us, so we operate with transparency, earning your trust through fair pricing and honest advice.
Reliable
With extensive experience in the commercial power sector, our dedicated team of engineers always find the right solution.
Family Values
It’s not just about business, we genuinely care about our clients and maintain close, respectful relationships with them. Your power really is our priority.
FAQs
Frequently Asked Questions
How accurate are these generator sizing calculators?
The results are accurate enough for initial planning, using common power factors and load assumptions. For final sizing, it’s always best to have a professional confirm based on your exact equipment and site conditions.
What power factor should I use?
Most generators and equipment are rated around 0.8 power factor, which is standard for general commercial and industrial use. Only adjust this if you have specific data from your equipment supplier.
How much extra capacity should I allow?
A 20% safety margin is built into our calculator recommendations to account for startup loads, power fluctuations, and future expansion.
Why do diesel and petrol generators have different fuel consumption rates?
Diesel engines are typically more efficient and use less fuel per kVA than petrol engines, especially under sustained loads. That’s why diesel generators are preferred for long-running or commercial applications.
For accurate recommendations, we suggest reaching out for a site review.
What is the difference between kW and kVA?
kW (kilowatts) measures real power, which is the power doing actual work.
kVA (kilovolt-amperes) measures apparent power, which is the total power drawn.
Because of efficiency losses, most systems operate at about 0.8 power factor, meaning 100 kW is roughly equal to 125 kVA.
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