KVA vs. KW How to Correctly Size a Backup Generator for UK Commercial Properties
                     KVA vs. KW: How to 
Correctly Size a Backup 
Generator for UK 
Commercial Properties
Understanding the 0.8 Power 
When it comes to safeguarding your business operations against an unpredictable grid, finding the 
best emergency power source in the UK is only Fhalaf thec battloe. Trhe real challenge begins when you look at the 
technical spec sheets of industrial plant machinery. Many property managers mistakenly assume that if their 
facility draws 80 kW of power during peak operations, they simply need to buy an 80 kW generator.
At Blades Power Generation, we see this exact sizing error all the time, and it frequently leads to overloaded 
systems, tripped switchgear, or damaged electronics. To keep your business running smoothly, you must 
understand the vital difference between Kilowatts (kW) and Kilovolt-Amperes (kVA).
The easiest way to understand the difference is that kVA represents total apparent power, while kW is the actual 
working power that performs physical tasks.
In standard UK commercial electrical engineering, three-phase generators are designed based on an assumed 
power factor of 0.8. This decimal represents the efficiency of your building's electrical system.
The mathematical relationship is straightforward:
kW=kVA×0.8
kVA=0.8kW 
Therefore, if your data logs show your facility requires a true working load of 80 kW, your backup plant actually 
needs to be rated for at least 100 kVA. If you buy a unit rated at 80 kVA, you will only have 64 kW of actual 
working power available, meaning your systemwill immediately overload when the mains power drops.
Account for Large Starting Inrush 
Another crucial factor we always remLinod oaur dcliesnts about is the inductive load spike. 
Equipment with heavy electric motors, such as commercial air conditioning, 
industrial water pumps, and large passenger lifts, requires up to three times more 
current to start up than they do to run continuously.
If your backup system isn’t sized in kVA to absorb these temporary startup spikes, 
your emergency supply will instantly stall out the moment it takes on the building’s 
load.
The Blades Rule of Thumb: Always calculate your peak concurrent kW demand, 
convert it to kVA, and add a 20% safety margin to handle future business expansion 
and motor starting currents.
Once you have sized your engine correctly, you need a smart way to bridge the gap 
during a blackout. An automatic changeover switch is the ideal solution here, 
monitoring the grid line-by-line and seamlessly transferring your critical kVA load to 
the generator within seconds of a failure.
Don't leave your site's operational resilience to guesswork or risky shortcuts. View 
our latest technical range at Blades Power Generation or contact our Gloucestershire 
engineering team today for an accurate, bespoke load evaluation.
Thank You
[email protected]
Sales: +44 (0)1453 799655 / 821322
Devereaux Crescent ,Ebley, England, 
GL5 4PX
United Kingdom