A 2kVA Dunlite diesel generator from 1960 .
To a large degree , this power factor is determined by the type of load connected to it . For instance , a phone charger or laptop power supply may have a power factor of one so , theoretically , you could run a 3500W power supply from a 3.5kVA generator , but that would be highly unlikely .
Heating elements , like those found in electric hot water systems , also have a power factor of 1.0 . They are referred to as resistive loads .
Other loads , like the electric motor in a rooftop air-conditioner , are inductive loads and they will have a power factor lower than 1.0 – usually between 0.7 and 0.85 .
Unless you know for sure , you should always assume the power factor of a load running from a generator to be 0.8 when comparing different model generators , regardless of what the specifications may state .
There ’ s another problem that we must understand about generator ratings . That 3.5kVA rating for the generator is , most likely , its peak output rating . It will only sustain that level of output in short bursts . Extended running at those levels will likely trigger the generator ’ s overload protection , or worse , cause it long-term damage .
What you need to look for is the generator ’ s nominal output . This is the maximum output level it can sustain over extended periods of running time without suffering permanent damage .
This will be anywhere between 15 and 25 per cent less than the peak rated output and it is usually only sustainable for four to six hours .
Can you see where this is heading ? Clearly , things are not entirely as they seem . The popular Gentrax 3.5kVA generator has a maximum output of 2800W and that is only for short bursts . Its continuous rated output is actually 3kVA or just 2400W for a 5.5-hour period .
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