12 or 24 volt...... that is the question

Hello,
We are installing an off grid system west of Phoenix, AZ. Which type of panel will provide the most "bang of our buck" a 12 V panel or 24 V panel. We are using both 12 and 24 V inverters. Should we use 12 V panels for 12 V inverter and 24 V panels with a 24 Invervter??? Setting up 3 inverter system with generator back up. Bottom line, if we need to purchase more panels, should we go for the 12V or 24V?????

Comments

  • mike95490mike95490 Posts: 7,723Solar Expert ✭✭✭✭
    Re: 12 or 24 volt...... that is the question

    Everything else being equal, 24V costs less in the long run. (48V even less!) The lower the voltage, the higher the amperage in the wire, which means more losses, and more expensive wire.
    Some controllers will take 80V from a string of panels, and down-convert it to 12/24/48 for charging.
    [ someone else here with one of those things - chime in]
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: 12 or 24 volt...... that is the question

    My thoughts - -
    If you're tending towards a small system with no plans to expand, stick to 12 volts, as many 12 volt items are available for a dime a dozen at discount stores, compared to 24 volt products.
    If however, you're looking at a larger and or expanding system, go for at least 24 volts.
    I started out 12 volts but grew far more than I ever dreamed (for me) and now, until my batteries need replacing, I'm stuck with 12 volts and the related drawbacks of using that voltage in anything but a small system.
    Where am I right now?
    Approx 1000 watts PV; Morningstar TS60; 6, L-16 batteries; 1/2 HP, 120 volt submersible water pump; Chest fridge, CF lights and all the other things to make life comfortable, along with several inverters for the various loads.
    I'm getting by on 12 volts, but especially with the relatively huge load of the pump, I'd be better off with the reduced wiring losses of 24 volts. Knowing what I know now, I'd have started out with 24 volts if I could have afforded it. The cheaper 12 volt products did on the other hand, permit me to get started in solar energy. Then I got addicted and where once I thought almost everything I would ever have would operate directly off 12 volts, now almost everything is run off inverters.! :-D
    All the best and good luck.
    Wayne
  • crewzercrewzer Posts: 1,832Registered Users, Solar Expert ✭✭✭✭
    Re: 12 or 24 volt...... that is the question

    Since you have both 12 V and 24 V inverters, and, I presume, separate 12 V and 24 V battery banks, I'd suggest thinking about going with just "12 V" PV modules. You can alway wire 'em in series to make 24 V, but it's usually tough to rewire a 24 V module for 12 V. Take a look at the Kyocera KC-130... reasonable size and weight, and, due to its high Vmp, it usually delivers good hot weather performance.

    I'd also look for a way to limit your system to just one or two 24 V inverters... this should improve overall efficiency.

    HTH,
    Jim / crewzer
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