new to solar,help with design

i am just getting started with solar and want to set up a system.we average about 59 kwh a day. i am unsure about a grid tie or battery. what i have read it is easier to grid tie and not have to mess with batterys. is this true. how many panels do i need? and what size? i live in texas so sun is not a prolbem. like i said i am new to solar and just trying to learn. please help


  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: new to solar,help with design

    59kWhr/day? ... well a gridtie system would be about 12kW of solar panels or about 100K installed .. add another 20K for batterys if you want to have backup abilities for that type of load

    Conservation is your first thing to look at and replacing energy hogs like older AC units ...
  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
    Re: new to solar,help with design


    Design system after optimal appliance and HVAC efficiencies are in place/replaced.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
    Re: new to solar,help with design

    If you choose Grid Tie--you will also need to check with your local utility to make sure that Grid Tie is allowed and what type of billing plan you have (1 year net metering is usually the best).

    You can also check if they offer Time of Use billing and see if the times work well with your solar power generation.

    A battery based Off Grid system would add quite a bit of expense to your system (you would probably need to replace your batteries every ~7-10 years) and would probably never be worth the money unless you have multiple power outages per year, or some other special issues with the costs/availability of Grid Power.

    Just as a very rough guess (without rebates, just cost of system divided by years of use and power generated; assuming retail costs and labor), your Grid Tie power will be in the range of ~$0.25 per kWHour, and an Off Grid system would be $0.50 to $1.00 / kWhr or more.

    You can check here for basic information on rebates, tax breaks, and net metering laws for Texas (plans differ by city and utility).

    Generally, only Grid Tied systems are eligible for rebates and tax breaks. Also, Grid Tie with 1 year net metering allows you to really shift your power generation/consumption across seasons--Off Grid, you can only store about 3 days of power with batteries--so there is significant power "lost" between seasons (or even during poor weather). Plus, you will probably still need a generator and fuel to make up for periods of poor sun/high power consumption--all adding to the bottom line $$/kWhr costs.

    Also, check you property tax rules--some states don't charge property taxes on the solar equipment--others do (and it may matter if Grid Tied or Off Grid).

    Almost always--it makes more sense to by new energy conserving appliances, install ground sourced heat pumps (for A/C and cooling) and adding insulation/double-triple pane windows, etc. to your home before you drop the first dollar on installing solar panels.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Roderick
    Roderick Solar Expert Posts: 253 ✭✭
    Re: new to solar,help with design

    If you're at 59 kWh a day right now, and saving money is your goal, then you might get good payback by going grid-tied and only generating a portion of your electricity. The idea is to trim the energy you're buying from the power company to the inexpensive lower tiers (assuming your rates are structured that way).

    Going completely off-grid would be very expensive for the amount of energy you're using. The others are right about conserving energy first, but taking realsitic considerations of lifestyle, it's likely that your energy usage is probably not going to go down even to half of what you use now, and the grid-tie will still be a clear cost winner.

    If you can post what your electric rates are today, people can likely give more detailed advice on what would make the most sense.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: new to solar,help with design

    I agree with all that has been said. Your cheapest energy dollar, certainly in the long term is reducing the load. Given your climate, HVAC upgrades to more effecient systems, adding sun shading awnings, trees to reduce load. Solar water heat, or demand gas fired, Hi ef appliances, adding insulation, lighting, phantom loads. Most if not all will cost less with more benefit than any PV system.

    Once you get the load managed if you are on the grid, it is the only system that makes sense. (Assuming that you can sell your excess production back to the utility). The difference between a 100kwh system and one of say 25kwh is huge.

    Do the research and do the math.