considering purchasing a kit...suggestions or recomendations.

ZedicusZedicus Registered Users Posts: 13
i am looking at a couple of 'expandable kits' but they really aren't what i want.

i am leaning towards kit from solarsystems, at 920w its nearly useless but it does have the grid tied with battery feature that i would like and i think i could rig some extra panels and accesories and get it to 1.25kw before blowing it up.

the kit from costco uses individual inverters so the entire inverter system would need reconfigured to get it to have battery + grid tied ability.

my goal here is around 1.2kw grid tied with battery functionality, around 2000$ (im dreaming there but as close to that for the materials.) i will have a separate installations budget to cover permits and the breaker box connections that i can't do.

im not against buyging the parts separately but i am trying to avoid spending 10 years on research myself, if you can recommend products from experience then that would be great stepping stone for me.


  • solar_davesolar_dave Solar Expert Posts: 2,367 ✭✭✭✭
    $2000 isn't gonna get you much and grid tie will go much further than a battery backed system. If the frequency of your outages is rare your better off getting a generator to cover the outages. Battery systems tend to drive the cost up substantially per kWh.
  • BB.BB. Super Moderators, Administrators Posts: 31,048 admin
    It is really back to what your needs are...

    If it is a few days to two weeks of backup power, and you have the room for a small generator and fuel storage (siphon fuel from car, natural gas, propane, etc.)--Then a genset is usually the most cost effective (and reasonably reliable) solution.

    If your needs are for 2+ months of backup power and it happens once or a few times a year, then a solar+battery bank+inverter can be very nice. Depending on weather/needs, a backup generator may still be needed.

    So--What are your emergency power needs. If lights, cell phone charger, laptop computer, small LCD TV--You can probably get away with a 1,000 WH per day or less (500 Watts of panel or so)..

    If you want to add a refrigerator--All of a sudden, you are looking at much much larger and more complex system. A full off grid cabin or very energy efficient home is probably in the range of 3.3 kWH per day.

    A very useful device is a Kill-a-Watt type meter. Plug in each of the 120 VAC devices you plan to use during an outage--And find out how may kWH per day they really use.

    We tend to underestitmate our energy usage and over estimate how much power we can get from solar... Really need to do some (relatively) design work and math to see what would work best for your needs.


    PS: Sorry, I forgot to add a link for the Kill-a-Watt so you can see what I am typing about: (link is from our host, Northern Arizona Wind & Sun).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ZedicusZedicus Registered Users Posts: 13
    solar_dave wrote: »
    $2000 isn't gonna get you much and grid tie will go much further than a battery backed system. If the frequency of your outages is rare your better off getting a generator to cover the outages. Battery systems tend to drive the cost up substantially per kWh.

    actually i have a natural gas line pre-plumbed to an unused portion of my patio so a generator and then a standard grid-tie system with out the battery bank would be a lot cheaper for the same power.

    honestly i continually revisit this problem around summer time because of a huge electric bill. (some of you may have seen my previous posts) the issue arises because of 2 things. i run a small data warehouse out of my basement. its power draw at load is not bad, about 900w. idle would be 500w but i never really sees idle. however if for some reason it does power off and has too boot up the we are talking near 2kw for about 30 minutes or longer while the system gathers composure and becomes usable. i would like to avoid ever having it in an 'off' state.

    on top of that my wife runs a 5 day a week daycare out of the main floor so the Air conditioner runs 24/7 for about 3/4 of the year.

    i have outfitted L.E.D. Bulbs and i use low power stuff where possible, and have done insulation thermal reflective tint, light colored shingles, blahblahblah. but when i can open a window in the middle of winter to help the house shed heat and the furnace almost never kicks on i am somewhat limited.

    my equation is not watts to maintain desired equipment (other then some way to maintain the servers and a generator can handle that) my equation is starting cost for a grid tie that will see an ROI in around 5 years. kansas has 2 things reliably, sun, and wind. i am in the city limits so erecting a wind turbine is not allowed. i could put in a 6KW system and never sell back to the grid so simply pushing say 2000$- 4000$ into a system that will lower my bill by even 100$ would be perfect. that would net me a goal in ideal condition of 40 months. factoring in loss to cloudy days, hail, and other losses, i could still see break even at 50 months.

    i am o.k. with a seemingly long ROI (even 100 months would not be out of the question) because the sooner i start, the sooner i will reach ROI and the problem will only ever get bigger.
  • solar_davesolar_dave Solar Expert Posts: 2,367 ✭✭✭✭
    You also might look at reducing the loads with some investment. More insulation for the AC days or a higher efficiency AC unit (mini-split) would help along those lines. I suspect with a sharp pencil and some shopping you could get the componets for about $1.50 to $2.00 a watt.
  • BB.BB. Super Moderators, Administrators Posts: 31,048 admin
    You might be looking at needing to really look at the home as an engineer would. Measure you heat inputs (waste heat from the computers, refrigerators, solar gain through windows/roof/etc., stove, TV, Lights, and even the warm bodies--Something like a 100 watts each for an average adult).

    It sounds like your internal heat (loads and people) are more than enough to keep the home warm even in much of the winter without the furnace. Conservation will help (if possible, reducing server loads -- 900 Watts is like running a mid-size space heater 24x7)--And looking at how efficient your cooling plant is.

    I am not sure, if your loads remain as is, other than if your A/C is very inefficient and perhaps improved ceiling/ducting insulation, it is difficult to see what else can be done to reduce power usage (other than a pure GT solar power system--if it can be done with your utility)....

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ZedicusZedicus Registered Users Posts: 13
    i have added all the insulation that can be added, i have cut EVERY light bulb and excess heat adder down to almost nothing. i have added hard power switches to TVs and small apliances so that they can actually be hard powered off when not in use. the server has high dollar high efficiency processors, and the most efficient high capacity storage available. i have moved some things to timers, i have solar tinted windows and i have even budgeted to go ahead and replace windows next year to true solar reflective high insulated windows. i am at the edge of things that i can make more efficient. i have a brand new refrigerator, it is one of the better rated ones in its class for efficiency.

    right now i can not replace the house HVAC, it will require tearing out a basement cieling and some other things that i just do not have the time for. i have considered adding a dedicated room A/C to the server room, but that will just shift the load from one area to another and if i decide to stop hosting the single room A/C will be a waste. HOWEVER if i were to add some solar power to my home i gain a tax credit, AND if i stop hosting the server i can keep the solar and it will still reduce the electric bill and help offset the EXTREME usage of what the house was.

    i have tried multiple times on multiple forums and i am a tad tired of people telling me to 'increase my homes efficiency.' no crap? i didnt just wake up yesterday and think 'lets add some solar panels...hyuckhyuck' i would honestly like some help planning a small to mid sized system that i could start with and that is capable of some growth. the panels will all sit on the roof, the usable area on the roof is low sloped with maybe a 45' by 30' area with 3 usable sides. say starting power requirements around 1.5kw but i would like to plan for growth up to maybe 3kw, if that is possible on my limited surface area. i can go grid tied with generator instead of grid tied with battery, i think that will get me the same results and be cheaper over all.

    not trying to be offensive. i know solar is not 'cheaper then grid power' but i will own its power creation and over time it will actually create an offset that will have an ROI instead of just buying grid power forever. if someone would like to help with this i would be appreciative. however if your recomendations can be lumped into 'increase efficiency' please keep them too yourself.
  • BB.BB. Super Moderators, Administrators Posts: 31,048 admin

    I am very sorry that we tend to get repetitive on energy reduction usage... We do not know you or your home to understand what you have done so far. And the forum is busy enough that I cannot keep track of what has been discussed in earlier threads for every poster.

    What confused me a bit was your looking at a 1,200 Watt of Hybrid power (GT and Off Grid Backup).-- That is not a lot of power for most homes. Using PV Watts, 1,200 watt fixed array, 77% average efficiency (in GT Mode, off grid would be around 52% efficiency), for Wichita KS:

    Solar Radiation
    (kWh/m 2/day)
    AC Energy
    Energy Value














    I don't know the price of power for you... PV Watts uses $0.077 per kWH for the estimated energy value per month. In my area with A/C and other heavy loads, it can be over $0.30 per kWH... So that small of system would offset between ~$11 to $44 per month off of your electric bill...

    And your bill may be 10x that amount? The small PV System would only supply a faction of that amount.

    A 1.2 kWatt system would supply only an average of 4.6 kWH per day (average daily production over 1 year)--Enough for a small/very energy efficient home/cabin with basic appliances (lights, refrigerator, clothes washer, well pump, TV, laptop computer, etc.).. But, I would guess, only a small faction of your present power needs.

    A hybrid power system is more expensive vs GT solar (solar panels+GT Inverter vs Panels+charge controller+batteries+Hybrid Inverter) and less efficient (running an off grid inverter system is ~52% eff vs a GT System running at ~77% of solar panel rating).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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