Generator Size Calculator
- Add running watts of loads used together
- Allow for the largest motor's starting surge
- kVA = watts ÷ 1,000 ÷ power factor
- Add a spare margin
Generator Size Calculator
Example figures only: replace them with your own. Results update as you type.
Starting factor and power factor are editable estimates; check the motor's rating plate and the generator maker's guidance.
Find Your Running Watts
Read the watts on each appliance's rating plate (or volts × amps). Count only what runs at the same time. Pumps, fridges, chillers and compressors are motors: they need extra power to start.
Generators
DAYLIFF DG1200S 1 kVA Petrol GensetKSh 26,100
DAYLIFF DG3800ST 2.8 kVA Petrol GensetKSh 50,370
DAYLIFF DG7500P 6 kVA Petrol GeneratorKSh 123,980| Product | Price |
|---|---|
| DAYLIFF DG1200S 1 kVA Petrol Genset | KSh 26,100 |
| DAYLIFF DG3800ST 2.8 kVA Petrol Genset | KSh 50,370 |
| DAYLIFF DG7500P 6 kVA Petrol Generator | KSh 123,980 |
Current listed prices incl. VAT (updated 4 October 2026).
Backup for water and dairy: backup generator guide. Solar instead? solar pump vs generator calculator.
Frequently asked questions
How do I calculate what size generator I need?
Add running watts, allow for the largest motor's starting surge, divide by the power factor and add a margin.
How many kVA to run a water pump?
It depends on the pump's power and starting surge; enter it in the calculator.
What is the difference between kVA and kW?
kW is real power; kVA is apparent power. kW = kVA × power factor.
Why do pumps need a bigger generator?
Motors draw a surge of power when starting.