What Size Generator Do I Need?

Ok so you’ve made the decision to purchase a generator. Personally I say well done. They are a great investment and can come in very handy as a back up power supply when remote area camping. Trouble is which one do you buy and what size does it need to be?

Let’s tackle the second question first. Generators are pretty much all rated in KVA or Kilo-Volt Amps. That not really very useful when all your 240v appliances are rated in Watts and KVA does not necessarily equal Watts.

To convert KVA to Watts, you need to multiply the KVA rating of the generator by the quoted 'power factor' of the generator. This should be stated in the specifications but is rarely stated in the advertising blurb. Honda quote a power factor of 1.0 so a 2KVA Honda generator will have a max capacity of 2000 watts. Whereas a Fuji generator has a power factor of 0.8 so a similar 2KVA rated unit is actually only rated at a maximum 1,600 watts.

The other thing many buyers overlook is the KVA rating quoted is generally peak, not sustained capacity. A Honda 2KVA will not last long if it’s made to continuously run a 2000w air conditioner for an extended period of time. Its continuous rating is actually only 1600 watts. Quite a bit less. What’s more, that continuous rating is only for a maximum of 3.4 hours.

So that expensive Honda EU20i generator your mate bought is only good for 1600 watts for no more than 3.5 hours…! Exceed any of that and you will start to do damage to the generator and shorten its life.

With that in mind, you need to now determine which generator will meet your real power needs. To do that, you need to determine what appliances you have and how many of them you may want to have on at one time. Here’s a list of some equipment we carry and their individual power rating in Watts.

Appliance Power Rating
Ibis Air Conditioner 1600w
Surburban Water Heater 1440w
CTek Battery Charger 25 amp 600w
Tetford 3 way Fridge 150w
Space Heater 1500w
Electric Blanket 120w
2 x Phone chargers 6w
Laptop PC power supply 60w
Microwave Oven 950w
Electric cooktop element 1000w
Electric Kettle 2400w
Electric Toaster 950w
Induction cooktop (twin plate) 2400w
Turbo Convection Oven 1400w

Now you will never likely need to run all your appliances at once but you can see from the above table, that the Honda EU20i will only run the air conditioner and nothing else. That may not be a problem if you don’t intend to run the air conditioner when you’re away from mains power. But if you do and you want to be able to charge your house batteries as well, you will need a bigger generator.

On the other hand if you only want to recharge your batteries, recharge a couple of phones and run your laptop for a while, you will only need about 700 watts capacity in your generator and most 1kva generators will manage that with ease. Just make sure the unit you buy is a pure sinewave inverter generator. That way you can run all your appliances including sensitive computer equipment.

Now that you’ve determined how big the generator needs to be, you can now choose what type you want. They are generally either Petrol, 2 Stroke or Diesel. I would avoid 2 stroke generators. They are old tech and produce a lot of fumes. Diesel are great but are seldom small enough to be contained in the average camper trailer or caravan. A petrol generator is probably the best all round option.

Now you have to choose a brand name or go for a cheaper unit. For many, Honda represent the best in quality generator products and I cannot argue with that. I had a small Honda for years and it never skipped a beat. Other brands with good reputations include Yamaha, Kipor and Hyundai. You also have a range of lesser known brands that you may be able to pick up at your local hardware or auto accessory stores. I have a Black Ridge generator I got from SupaCheap Auto which has been as reliable as my Hondas was.  Finally, you can get a cheap brand of the internet, with Fuji-Micro and Gentrax being very popular.  Again, I have a Fuji Micro 4.4kva generator that I got for our caravan and it has worked perfectly on the few occasions I've needed to use it.

What you chose will depend on your budget and the capacity you can get for that budget. For my thinking, getting an expensive brand name for something that you may use very rarely is false economy. A 2kva Honda generator can cost around $1,900. A similar rated Gentrax generator costs around $440 or $560 for a 4.4kva unit with double the capacity. At those sort of prices, you can afford to replace it 3 or 4 times for the cost of one brand name unit.


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