How big a generator do I need?

Discussion in 'Off Topic [BG]' started by megadan, Jul 23, 2009.

  1. Hey TB, hope you can help me with your collective smarts.

    We're thinking about taking a trip down to the camp next weekend, it's on the lake, no neighbors for miles around.

    I want to take some gear and have a little weekend jam session.

    To get over acoustic drums, I'd probably want to power at least:

    -one small (Peavey powered head and 2 12" monitors) PA system.
    -one decent sized bass amp (probably my GK1001RB through a 1x15)
    -two tube guitar amps (15" combo and a 4x10 stack)
    -lots of misc. small devices: 3 - 4 keyboards, pedals, drum machines, etc.

    Generator rentals are pretty reasonable ($30 - $50 a day from what I'm seeing), but I have no idea what size I would need to run all that stuff. The options in my price range are around 2500 - 5000W
    You can see my choices here:

    How do I know what size I need?

    Thanks in advance.
  2. kesslari

    kesslari Groovin' with the Fusion Cats Staff Member Gold Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
  3. Hi.

    Usually the generator size is calculated by the max power draw of the individual components. Then multiplied by 2.

    For example:

    PA ~ 300W
    Bass ~ 400W
    Guitars ~ 2*300W
    Misc ~ 500W

    The rated RMS output of the amps would be half of that, or the needed power twice the output of the amp. Which ever way You want to look at it.

    When You have the power consumption, 1800W in above scenario, double it. That's because the generators usually are rather slow to react to the voltage draw changes and that obviously can harm the amps and/or pop the fuses.

    You're playing in the dark???

    Lighting draws huge amounts of power and can bring even a decent size generator to its knees.

  4. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois

    I'd estimate the absolute maximum total number of watts used .

    small PA - 1,200 w
    bass amp - 1,000 w
    2 guitar amps - 400 w
    misc devices 200 w

    I would say the most you'd need is total - 2,800 w.

    I know from experience that I can power my own band which is about equivalent in output to yours, with a 2,500 w generator through a single power distributor/voltage regulator that was rated at 1,800 w.

    But make sure you include a margin of error for power surges in the generator and also in case you decide you need to run lights or something else.
  5. Thanks all. Looks like around 3000 - 4000W is what I would need.

    most of the jams would be during the day, so lights shouldn't be too much of a problem. Maybe one or two regular household lamps.

    Is there anything obvious I'm missing? I've never done this before.

    Most generators have one or two 20A 120V outlets, or a 30A outlet, plus a big 240V for household stuff that I wouldn't use.

    Is it safe to say that if we can power all our gear off a single 15A outlet in a cottage (an unrelated trip) that we should be ok to power off a generator with a 20A outlet?

    Put another way: is any generator with a 20A outlet presumably large enough to power our gear?
    My mind is missing the connection between wattage and current; I know the math and formula's I'm just having a hard time wrapping my head around. I'm used to thinking in A's, like, I have a 200mA boss adaptor and 3 40mA pedals to power. Can I use this same logic and just scale up for a this application? If I keep it under 20A am I ok?
  6. Philbiker

    Philbiker Pat's the best!

    Dec 28, 2000
    Northern Virginia, USA