Home Generator Size Calculator
Select appliances, add a buffer, and get the best PRAMAC match.
Home Generator Size Calculator
Select appliances, add a buffer, and get the best PRAMAC match.
1) Basics
2) Add appliances
3) Your load
4) Recommended models
Appliance Library
Frequently Asked Questions – Generator Size Calculator
-
The size of generator you need depends on the total wattage of the appliances you want to power. Use our free Generator Size Calculator above to add appliances such as fridges, lights, heating, and computers. The calculator will show you the total load in kVA and recommend the most suitable PRAMAC generator model.
-
Each appliance has a running wattage and sometimes a higher starting (surge) wattage. Add up the running watts of all appliances you want to power, and include a 20–25% buffer for surge loads. Our calculator does this automatically to save you time.
-
kW (kilowatts) is the actual power used by your appliances, while kVA (kilovolt-amperes) is the apparent power rating of the generator. In most UK homes a power factor of 0.8 is used, meaning a 10 kVA generator provides around 8 kW of usable power.
-
For essential home backup (fridge, lights, boiler, internet, small appliances), a 3–5 kVA generator is often sufficient. For whole-house backup including heating, air conditioning or electric ovens, you may need a 7–10 kVA generator or more. Always size slightly above your maximum requirement for reliability.
-
Yes, many UK homeowners use portable generators for backup power. Models like the Pramac ES4000 or PMi2000 provide reliable portable solutions. For seamless automatic switching, a standby generator with transfer switch is recommended.