house load and inverters

please help me get this figured out.I checked my breaker box and have all my lights and recepticles in the house on one side of the breaker box and have the outside lights ,frig. and stuff on the other side and the only 220 appliances i have is stove and dryer.if i use a 2000 watt inverter with solar panels then the inverter will power most of the load on that side of my breaker box and use grid power to make up the difference? But what happens when I'm not home and using the power from the inverter as my light company is not set up to buy back electric from its customers but are planing for it in the next couple of years? And will the inverter quit producing ac voltage if the grid goes down? I'm just looking for a way to get my light bill down i have allready installed cpf bulbs and smart power strips with timers on the kids TVs and lights and a programable thermostat and added more insulation and have dropped the bill from $250 a month to $160 and would like to get it down around $100. AND i can get all the 2 year old 8 D, 4D and group 31 batteries maintained on float chargers and equalized once a month i want from my job so can i program a system to charge the batteries and use them in the evening until they get down to 60 to 70% charge and then switch back over to the grid?
sorry for the long post but the only solar around here in Tennessee is mainly solar water heaters and i have been unable to find anyone around here to help with the electric solar questions.

Comments

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: house load and inverters

    kg,

    You’ve clearly made a lot of energy conservation progress by cutting your monthly electric energy bill from $250 to $160. Assuming an average rate of $0.10/kWh, your family is running through ~1,600 kWh/month, or ~53 kWh/day. Considering the appliances and loads listed (water heater and furnace are gas?), that’s still a pretty high rate of energy consumption.

    In fact, 53 kWh/day means an average load of 2200 W all day long. Removing the stove and the dryer would obviously reduce the average load, but factoring in high daytime loads and low overnight loads would likely push the average load back into the same region.

    Peak loads would of course be higher. For example, our “12 Amp” upright vacuum cleaner alone draws ~1,440 W while in use. Accordingly, I suspect that a single 2,000 W inverter won’t be able to handle the loads you’ve suggested. You’ll need to do some more homework on what your actual loads are. I recommend you buy a Kill-a-Watt meter (~$30 or so) for that purpose.

    http://store.solar-electric.com/kiacpomome.html

    Even if you are able to reduce your energy need to 1,000 kWh/month, it’ll be impractical to have a PV energy system large enough to ever be able to sell back to the grid. Assuming 67% overall system efficiency and 5 “hours” of daily insolation, you’d need an array rated at ~10 kW STC just to meet your need average daily need. Anything that you “sold” to the utility during the day would be bought back at night.

    I’m sorry about all of the bad news. However, all’s not lost, as you have a couple of options.

    It’s generally cheaper to invest in conservation that it is to generate energy. Accordingly, I recommend you keep looking for places to cur energy consumption. For example, a brand new Sears Kenmore Energy Star 21.7 cf fridge (item # 64242) is currently priced at $620 and consumes but 448 kWh/year, or 1.23 kWh/day. I believe it also qualifies for an income tax credit this year and next.

    You may be able to develop and deploy a “hybrid” system using Outback inverters. When used with a Mate, there are two features that might be of interest to you. One is called “HBX Mode”, which powers loads from the batteries as long as they’re above a certain voltage. Once the batteries fall below the set point, the inverter connects the loads to the grid and, along with the PV array, can charge the batteries.

    http://www.outbackpower.com

    Another feature is the “Grid Use” mode. This mode determines what times of day the loads are powered from the grid or from the PV array and batteries. Used along with your utility’s Time of Use (TOU) schedule, the inverter can power loads from the PV array and the batteries during peak rates and the use the grid to power your loads and help recharge the batteries during off-peak rates.

    Of course, the inverter will use the batteries to power your loads during a power outage.

    I hope this info is useful to you.

    Regards,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: house load and inverters

    thanks for the help and yes my water heater and furnace are gas and i have installed the 90+ versions that remove the heat so well that the vent pipes are regular 4" PVC pipe and i have the new GE washing machine that is energy star those will be tax credit for 06 and for tax credits 07 i will buy the matching dryer in January and a new fridge most likely in February or march. i just want to use the solar to help power 2  TV's and lights during the day after 3 O'Clock when the kids come home from school and early evening. I just want to use morning sun to charge the batteries when no one's home and afternoon sun and batteries for evening use just to offset the use of grid power and i am not concerned with selling back to utility company. i checked Outback and found the

    Grid-Interactive Applications
    Sealed, 60 amp AC input, 120 VAC/60 Hz (Turbo included)
    GTFX2524 2500 W, 24 VDC, 55 A charger $1,995

    would this be able to charge my batteries or would i need to add a controller and will it tie into my breaker box and suppliment utility easily without to many problems?

    thank you
    Kevin
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: house load and inverters

    53 KWh/ day is still pretty high with gas hot water. I assume air conditioning is not included in this number.

    Depending on where you live and air conditioner / heater (assuming electric) the order for general residence is:

    1) Air conditioning / heating
    2) Hot water heater / clothes drier.
    3) Refrigerator
    4) Stove
    5) everything else.

    Hot water heater, washer, and electric clothes drier go hand in hand. Assuming electric drying, the more wash, the more hot water, the more drying.

    If you have a swimming pool, that move up to number 2 or 3 on the list as a 1 to 2 hp motor run 7 or 8 hours is quite a bit of KWH's.

    You can get a reasonable mapping with a clamp on ampmeter, checking running current then guesstimating duty cycle per day.

    Although not critical, you usually like to statistically level the 120 v loads to equal each sides of the mains. Total for 120v does not usually make for more then 10-15% of overall electric bill, unless you have some stupid things like several 150 watt flood light bulbs you run all night.

    New refrigerators are about 2 kW-hrs/day. Ten year old refrig can be double this.

    Large screen TV's run 8 to 12 hrs a day can run up the bill, but still only worth 2-3 KWH/day.

    I live in FL so Air Conditioning is major. Here is my list in order with A/C averaged across year.

    Air Conditioner 25 kW-H /day. 48% of total
    Water Heater 11.5 kW-H /day, 23% of total
    Refrigerator 4.1 kW-H/day, 8.6% of total (ten years old 27 cu-ft, needs to be replaced)
    Clothes Dryer 3.8 kW-H/day, 7.8% of total
    Inside Lights , about 1.5 kW-H/ day
    Range Oven, 1 kW-H/day (wife believes frying is un-healthy)
    Dish Washer (almost 1 kW-H/day)
    Range Large burner
    Outside Lights
    Kitchen Plug-In Appliances
    TV's
    Clothes Washer
    Range Small burner
    Range Broiler

    My biggest bang for buck would be solar hot water heater.


  • System2
    System2 Posts: 6,290 admin
    Re: house load and inverters

    I saw HUGE savings at the camp this past Summer, after installing Solar hot water and converting to a Chest Fridge run off PV. Bill went from around $160.00, down to about $30.00!! No kidding!
    Late Fall and Winter are still a problem though, as "The Fall Rains" get going and we have very little sun fore 2 or 3 months. Lots of short, dark, cloudy days.
    Wayne
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: house load and inverters
    i just want to use the solar to help power 2  TV's and lights during the day after 3 O'Clock when the kids come home from school and early evening. I just want to use morning sun to charge the batteries when no one's home and afternoon sun and batteries for evening use just to offset the use of grid power and i am not concerned with selling back to utility company. i checked Outback and found the

    Grid-Interactive Applications
    Sealed, 60 amp AC input, 120 VAC/60 Hz (Turbo included)
    GTFX2524 2500 W, 24 VDC, 55 A charger $1,995

    would this be able to charge my batteries or would i need to add a controller and will it tie into my breaker box and suppliment utility easily without to many problems?

    Kevin,

    Since you’re not planning on selling back to the grid, you won’t need a grid-interactive inverter. I suggest you consider the OutBack FX2524T instead.

    See: http://store.solar-electric.com/fx2524t.html

    This inverter can use the grid or an AC generator as a 120 VAC power source for charging the batteries and/or powering loads if the batteries are too low. It cannot charge the batteries from a PV array, so you’ll need a charge controller like OutBack’s MX60 for that purpose. With a Mate and a Hub, the inverter and the charge controller will coordinate their functions and activities. The Mate is required for advanced inverter programming anyway.

    A 2500 W inverter should be able to handle the loads you’ve described with ease. One way to hook everything together would be to disconnect the circuits you plan to use from your present AC distribution box and rewire them to the load side of another small box with new load breakers. Use your main AC distribution box (and a big breaker) to feed AC to the AC input of the inverter, and connect the inverter’s AC output to the line side of the new small box.

    The MidNite Solar E-Panel is a tidy way of electrically, mechanically and safely integrating all of this stuff together. See: http://www.midnitesolar.com/MidNite-Products.html  Inverters hum when they’re operating, and some find the noise to be distracting or even annoying. My FX2524T inverter is located in my garage.

    HTH,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: house load and inverters

    got the light bill in we used
    1329 kilowatt hours     110.60
    water                           18.40
    sewage                        24.59
    gas                              14.87
    total                         $168.46

    if i did the math correctly thats  42.87 KWH a day at .08/kWh

    Aug was 2396 KWH  plenty of days 95 to 100 degrees before i installed the new a/c heat system and added insulation
    september was 1921 KWH thats a 475 KWH drop with only new a/c and insulation
    October was 1679 KWH thats a 242 KWH drop with new washer (dropped water and sewage greatly) and CPF bulbs and smart strips and cooler weather




    it's amazing how little things such as smart strips and cpf bulbs can affect the energy useage in a 2500 sq foot house with 3 kids
    i hope to see that drop more with the new fridge and new dryer when i buy them in the next couple of months

    so i would need to connect the PV array to a disconnect then into the mx 60 and the batteries to the mx 60 and then connect the mx60 to the outback inverter which connects to the breaker box and i can program this to run these circuits and charge the battries while the sun is out and use the batteries until a low voltage set point then have it use the power company.
    Will it then be OK to wait until the sun comes up to bring the batteries up to full charge?
    if i am not using the all available output from the inverter say 1000 watts instead of the 2500 watts what will happen to the extra available electric or will the inverter only put out what electric is drawn from it?
    what will stop the inverter from sending voltage back down the utility lines during a power outage?

    sorry for all the simple questions but i would hate to spend the money and not be happy or have major headaches with the system.
    thanks for all the help
    Kevin
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: house load and inverters
    so i would need to connect the PV array to a disconnect then into the mx 60 and the batteries to the mx 60 and then connect the mx60 to the outback inverter which connects to the breaker box and i can program this to run these circuits and charge the battries while the sun is out and use the batteries until a low voltage set point then have it use the power company.
    You’re close. The batteries get connected to the MX60 and to the inverter. Here are some sample drawings to help give you a basic idea:

    http://www.outbackpower.com/pdfs_wiring_diagrams/ps2ac-dcsingle.pdf
    http://www.midnitesolar.com/e-panelWIRE1revC.pdf
    Will it then be OK to wait until the sun comes up to bring the batteries up to full charge?

    Yes.
    if i am not using the all available output from the inverter say 1000 watts instead of the 2500 watts what will happen to the extra available electric or will the inverter only put out what electric is drawn from it?

    The inverter (along with the grid, a generator or the batteries) will only supply the power required by the loads (up to its limit, of course).
    what will stop the inverter from sending voltage back down the utility lines during a power outage?

    OutBack’s grid-intertie inverters (i.e., those with a model designator beginning with the letter “G”) include a special circuit that senses the grid voltage. If the grid fails, the inverter quickly disconnects and will not reconnect until the grid has been back up continuously for 5 minutes. This is a UL required “anti-islanding” feature.

    Outback’s backup- and off-grid inverters can accept power from the grid or a generator, but these inputs can’t send power to those sources. These inverters' AC output should not be connected to the grid.

    HTH,
    Jim / crewzer