How can I tell if a generator is big enough?

Question

Could somebody please explain how I can tell the output of a generator.. the one I have looked out says 7-8 kvs( i think that is right)

I am needing power to a mobile home. I will need lighting/tv/computor(maybe but could live without it) and possible a small oil heater ??

Answer 1

I work in the hire industry and i get asked this all the time, 1Kv is approximately 800watts, and 1Kw is 1000watts, now you will be surprised but to just run a kettle you will need more than a 3.5Kva geny, you don't say what you are doing with the geny but a 8Kva would run a kettle and a small microwave, but not a heater at the same time, you could run a TV, fridge and possibly a small heater, give me some more info and i will try to help.........
Right i'm back, lighting is fine, florecent tubes and normal bulbs make hardly any difference, the oil heater is on/off so although it will pull some current 7.8Kva will do it, the problem comes with the computer, a generator although it seems like it does, it does'nt generate a constant stream of electric, it fluctuates with the engine revs, not alot but ever so slightly and this is enough to cause the computer to fail and cause quite alot of damage, your geny might have a filter fitted which will even out the current but check this before pluging in, you might also want to think about getting a "Super silenced" geny these are the same but are contained in a sound proff box (For want of a better word) and make living next to a running geny alot more comfortable, i hope this helps.......................

Answer 2

Unless you have an electric cooker (6-7kW) or an electric shower (8-10kW) then 5kVA should be plenty for a house. All generators have circuit breakers, and the worst that can happen is that the breaker opens and everything suddenly stops working. Add up all the wattages of the individual appliances. If it comes to less than 4000 (allowing for a power factor of 0.8, which is reasonable; filament bulbs and heaters are 1.0, anything with a motor or transformer will be less), you're fine. Just be careful how you wire it in. Best way is to let the meter run out, disconnect the tails from the consumer unit, tape up the ends securely (better: wire them to separate terminals in a heavy-duty junction box, and nothing else) and connect your generator where the meter tails used to go. This way, you can't be powering the whole street (and you're not going to be dishing out nasty surprises to people working on the substation). If you can't wait for the meter to run out, or you are on a bill meter, then you can make the meter tails safe by cutting the seal on the company head and removing the main fuse. But note you *cannot* legally put this back yourself; it's the property of your local electricity supplier. You will have to get them to replace it when you want to go back on the grid, and they may charge for the callout unless you can get them to fit you in between nearby jobs. If you need to switch back and forth often between mains and home-generated power, ask your local electricity supplier about fitting an approved changeover switch. You can buy the equipment they specify from any electrical factor, and get them to make the final connection.

Answer 3

( Spud--1Kv is 1000 volts not 800 watts. 1Kva is 1000 volt/amps which at 240volts is 4.17 amps or 1000 watts.)

Most kettles are about 2.5kw which is 10-11 amps. The generator will be marked as 7 or 8 Kva which means, assuming it's a 240 volt output that it is capable of 7-8000 watts or 30+ amps. You will have to add up your various appliances to see what you need to use at one time to make sure that the total is within the capacity. The computer should be ok as long as the output is stable, the psu should be able to cope with minor fluctuations.

Answer 4

Kva is about a KW - a tiny bit less. That generator will run quite a lot and may use more fuel than you need for your requirements. It will run lights and even an electric fire which takes about three KW. Make sure it is 240V if you are in UK

Answer 5

I have a 5500 watt portable generator for emergency use. It connects via a transfer panel and powers 12 circuits. It will power the refrigerator, freezer, microwave and toaster ovens, furnace, well and septic pumps, most lighting, television, computer, and a few wall outlets. Not everything can operate simultaneously, but we can carry on with most normal activities.
I'd expect you would have no problem with a 7.8kVA generator to power most of your home.
Have a look at my generator page for other safety and connection ideas.
http://members.rennlist.org/warren/generator.html

Answer 6

Its actually saying 7.8 kva
Little learning. maybe, you are used to WATTS as a rating on a lamp, this is a pure product of AMPS XVOLTS. AMPS X VOLTS = WATTS.
That is true when you are dealing with DC (like your car battery) or a purely RESISTIVE load on AC (for example, a lamp or convector heater.) But, as soon as an INDUCTIVE load on AC(anything with a motor, like a fridge or vacuum cleaner) is in the discussion, we start talking of the POWER factor, which is 0.8 for an inductive load.
Thus, your 7.8 kva genny will supply 7.8 kv for heaters etc, but only 7.8 X 0.8 for inductive loads.(6.24 kva)
My suggestion from experience .is to derate the genny by 0.6, 7.8X0.6 kva, this will allow for the start current on inductive motor, which is of the order 8 XNormal full load. Thus, if the fridge normally runs on 2 amps, the instantaneous load on start may be 16 amps.

Answer 7

I use this chart.
http://www.yamaha-motor.com/outdoor/generator/sizing.aspx
You should allow for a greater load than you expect when you buy a generator.