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  1. #1
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    Default How much power does an Inverter "waste"?

    Despite my nickname I don't really have a "Planta full"

    I have been in Santo Domingo for a few months without planta or inverter and while it has been okay, now the electric has been getting worse. I'm looking into getting a 1.5 Trace with 4 batts directly from the Trace shop, however I would like some opinions on my biggest worry: The increase in electric costs upon running the inverter. I do have electric bills around 1200 to 1800 Pesos/month running computer and TV almost all day and an bedroom AC at night (not on freeze mode, just 78 degrees).

    What kind of extra power does the Inverter waste when charging. I mean what is the ratio of charging compared to what the batteries deliver once the power is out. So far I can only guess from my neighbors' electric bills, some of which have inverters but don't even run TVs and computers all day as I do but still have electric bills in the 3000 to 4000 range. Is it that bad?

    Best would be experience from someone who has gone from no inverter to inverter without changing his habits. How much do the bills really increase?

  2. #2
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    Default Dominican Math

    A good layman's guess would be a loss of 20% going both ways. That is to say, converting the AC to DC and vice versa.
    However, bear in mind that your light bill will go up by more than that, as you will now have 24 hour power.
    So, if you average 16 hours of power/day at the present time, then you would be using 50% more power to have 24 hour power, plus the 20% of the 8 hours on battries and maybe 4 hours charging, so you would go from paying for 16 hours of power/day to 31.
    In that scenario, your light bill would increase by almost 100%.
    Then again, the quality of your life will also increase by 100%.

  3. #3
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    Default

    That sounds like fuzzy math to me?

  4. #4
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    Quote Originally Posted by rellosk
    That sounds like fuzzy math to me?
    No doubt about it.
    But the result is there.
    As nobody knows how much power the OP gets per day, it can't be calculated exactly, but, it's a formula that is fairly accurate, as to how much more the power bill will be.

  5. #5
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    Quote Originally Posted by Rocky
    No doubt about it.
    But the result is there.
    As nobody knows how much power the OP gets per day, it can't be calculated exactly, but, it's a formula that is fairly accurate, as to how much more the power bill will be.
    Sorry, I was just trying to be funny.

    No doubt your formula provides a good guide. It's in line with another thread where someone said it was costing them RD1000-RD3000 to charge the batteries, assuming there were no blackouts.

  6. #6
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    Rocky: Thanks for the dominican math lesson In my case it should be safe to say that more power usage due to increased availability is excluded from the formula since the Zone I live in used to have constant electric with max 1 hour per week outage (yes per week, wasn't worth getting an inverter for that very reason). One day about 3 weeks ago all the sudden things changed from that heaven to 5 or 6 hour outages per day. The neighboors think some gov-official must have lived here and has now moved away.

  7. #7
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    Quote Originally Posted by PlantaFULL
    Rocky: Thanks for the dominican math lesson In my case it should be safe to say that more power usage due to increased availability is excluded from the formula since the Zone I live in used to have constant electric with max 1 hour per week outage (yes per week, wasn't worth getting an inverter for that very reason). One day about 3 weeks ago all the sudden things changed from that heaven to 5 or 6 hour outages per day. The neighboors think some gov-official must have lived here and has now moved away.
    In that case, you won't get much satisfaction paying a higher light bill, now that you've been spoiled for so long.
    Nevertheless, the good news is that you'll be able to get back to your normal life, as it was before, and always have power.
    May I suggest you purchase some of those soft glow low consumption GE light bulbs.
    They will go a long way in reducing electrical consumption and maybe your light bill will still be acceptable.

  8. #8
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    Default Twisted brain

    Quote Originally Posted by newuser
    I am not following this math well. Using your example the OP would be using (and paying to an EDE) 16 hours of power per day.

    While the inverter is supplying power the other 8 hours per day the OP is not paying EDE for this power. He is getting the power from the inverter. Therefore the 20% conversion loss and the 50 % more power have no bearing on the EDE bill.

    Charging the batteries would be the only additional charge on his EDE bill. What am I missing in this formula?
    I am not surprised that you are not following it, as I didn't explain it well.
    Let me try another way.
    There is approx. a 20% loss in converting from battery power to AC, and the same applies to recharging the batteries.
    In the scenario mentioned in my first example, one has to replace the 8 hours of power supplied by the batteries, by way of charging the batteries up the amount they lost while in use, then you add the 20% for the DC to AC, plus another 20% in the charging process.
    If I may use an another example...
    If you were pouring 1/3 of a 5 gallon bottle of water into another without using a funnel and were losing 20% while doing so, when you replaced the water into the original bottle in the same way, not only would you need the 20% lost pouring it back in, but the 1/3 of a bottle as well.
    In other words, 1.66 gallons plus 20% pouring it into the empty bottle = 1.992 gallons, then to refill the original bottle, 1.992 plus 20% = 2.3904 gallons.
    To relate it back to the power bill, if you were only receiving 16 hours of power/day, that would be equivalent to 2/3 of a bottle = 3.33 gallons.
    The additional 8 hours of power you would get by having an inverter is like the 2.3904 gallons you had to replace to fill the bottle.
    That would represent an approximate increase of 70% on your light bill.
    There's nothing wrong with the math. There's something wrong in the way I explain it.
    I hope it's a bit more clear this time.

  9. #9
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    There is another point.
    When you do use inverter, remember to use low consumption bulbs that use between 15-20 watts maximum. This alone will save you some money on your bill. When the lights are out, the inverter will turn on but remember, your fridge and a/c and water heater is off so you are not using that much power anyway. Remember, inverters are only used as emergency power source. You can't connect everything to it if your capacity is only 1.5 Kilo. If you are using 4 batteries then don't even think about connecting the full size fridge.
    So in simple words, your bill should not jump so high because you have already reduced the energy consumption of bulbs by huge percentage. Then your inverter is not really running everything in the house ex: a/c, fridge, washing machine, water heater etc etc. In conclusion, I don't think you will see a huge jump in your light bill.
    Good luck.
    AZB

  10. #10
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    Quote Originally Posted by newuser
    I am not following this math well. Using your example the OP would be using (and paying to an EDE) 16 hours of power per day.

    While the inverter is supplying power the other 8 hours per day the OP is not paying EDE for this power. He is getting the power from the inverter. Therefore the 20% conversion loss and the 50 % more power have no bearing on the EDE bill.

    Charging the batteries would be the only additional charge on his EDE bill. What am I missing in this formula?
    Keep in mind your inverter isn't giving you "free" electricity, you only get out what you put in, minus the loss of efficiency from conversion, which I think I heard was close to 9% on some of the better model inverters, but also has to do with the voltage coming from the street. In areas where the EDE is spreading things too thin, a frequent result is that the street voltage is low, sometimes as low as 80 volts (I have even heard of 60 but never seen this myself) any lower than 90 volts and most inverters wont charge your batteries at all, in fact they may assume theres a blackout and start inverting instead.

    I was involved in an experiment to design an inverter that could charge at 80 volts, but the efficiency was so low (like maybe 50%) that it just wasn't worth it.

    Basically I learned that the lower the input voltage, the poorer the efficiency of the charger.

    Another thing you need to remember in regards to your bill is that the power company charges you much more if you use more, since they assume you're a rich guy who can afford it if you have so many appliances.

    I don't mean the obvious increase in KWH you get billed for, I mean the price per KWH will increase as you consume more. Kind of like a reverse discount for buying in bulk, or maybe you prefer to see the glass as half full and call it a discount for conserving energy you no longer qualify for at that point.

    There is a breaking point which I seem to recall is around 700KWH /mo where your bill can practically double from 699KWH to 700KWH since the rate increase is pretty drastic at that point.

    Happenned to me once and I stopped using my air conditioner completely.

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