How much power does an Inverter "waste"?

PlantaFULL

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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?
 

Rocky

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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%.
 

Rocky

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rellosk said:
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.
 

rellosk

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Rocky said:
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.
 

PlantaFULL

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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.
 

Rocky

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PlantaFULL said:
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.
 

Rocky

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Twisted brain

newuser said:
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.
 

AZB

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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
 

MrMike

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newuser said:
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.
 

americanized

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A few specific questions.

I am a newbie about inverters in general, but have a few imortant questions, so any help would be appreciated.

1) Can an inverter supply current while it charges?

2) For a 3.6KW /8 battery Inverter, how big of an generator is needed to charge it (assuming no other component is being supplied)?

3) For a 3.6KW /8 battery Inverter, how long is needed to fully charge it?

4) For a 3.6KW /8 battery Inverter, how long can it run before running out of power, assuming being fully used (3.6k), from fully charged?

Thanks in advanced.
 

Rick Snyder

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No electrician

I too am a newbie concerning inverters and my story is as follows:

1. I get about 16 hours of power daily.
2. My monthly electric bill is a flat $500 pesos a month.
3.Electronics in the house requiring 24 hour service would be one refrigerator, one computer, 3 televisions, 3 fans and 3 lights more or less.

When the power to the house is below 110 volts I have a step-up transformer that I switch on to increase the power to either 110 or 120 volts.

The use of an inverter I think is a must as my power bill is always $500 pesos and never more.

The question is what size of inverter should I get and the estimated cost of such an item to include installation as I'm no electrician? Where to purchase it and who would install it way out here in El Seybo? Thank you.
 

Rocky

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americanized said:
1) Can an inverter supply current while it charges?
Yes


americanized said:
2) For a 3.6KW /8 battery Inverter, how big of an generator is needed to charge it (assuming no other component is being supplied)?
There are many factors to take into account.
I manage with a Honda 2.8, but I turn down the charge rate on the inverter to approx. 30 amps at 24 volts, while operating other light loads.
If you want to charge it as fast as possible, you would need at least a 7K unit, and even then, you would be running it hard, so typically, one might have a 10k unit for a deluxe package.



americanized said:
3) For a 3.6KW /8 battery Inverter, how long is needed to fully charge it?
Depends how low the batteries are, the brand of inverter and size of it's charger, the quality, age and amperage of your batteries.
That being said, typically, if you drained the batteries and the current coming into your house is at least 100 volts, it might take 8 to 12 hours.


americanized said:
4) For a 3.6KW /8 battery Inverter, how long can it run before running out of power, assuming being fully used (3.6k), from fully charged?
One would never run it at full rate, any more than one would drive a car at top speed for an extended period of time, as you would burn out the equipment in no time.
There are formulas to calculate how many batteries you would need to last a given period of time, with a given load.
One should try to not use more than 2/3 power, so the equipment is just cruising and gives you years of good service.
 

Rocky

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Rick Snyder said:
I too am a newbie concerning inverters and my story is as follows:

1. I get about 16 hours of power daily.
2. My monthly electric bill is a flat $500 pesos a month.
3.Electronics in the house requiring 24 hour service would be one refrigerator, one computer, 3 televisions, 3 fans and 3 lights more or less.

When the power to the house is below 110 volts I have a step-up transformer that I switch on to increase the power to either 110 or 120 volts.

The use of an inverter I think is a must as my power bill is always $500 pesos and never more.

The question is what size of inverter should I get and the estimated cost of such an item to include installation as I'm no electrician? Where to purchase it and who would install it way out here in El Seybo? Thank you.
First thing is that you need not bother with the fridge, as you get more than enough daily power to keep it cold enough.
The fridge not only requires a bigger inverter, but uses up the batteries a heck of a lot faster, plus, you would need to buy more batteries than if you don't hook the fridge up.
A Trace/Xantrex 2.4 with 8 batteries would be ample and would be a deluxe set up, and could include a fridge.
You could probably get away with a 1.5 with 4 batteries, specially if you use low consumption light bulbs and no fridge.
I live in Sosua, so I don't know where you can buy in your area, but I assume Higuey is the closest big town to you.
Let the people who sell you the inverter hook it up for you and don't pay them the full amount, until it's completely installed and operational.
Let them know what you want hooked up, and what you don't want.
 

americanized

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Thank you very much Rocky.

I am building a midsize house in the near future and I'm thinking of solutions to the eletricity problem. I am thinking of having two 3.6k Trace connected in parallel with a least 12 batteries to provide for my current needs. I spoked with a Trace rep down in Santiago in my last trip, but either she was not knowledgeable or was BSing me, talking about only a 4 hour run for such system. I came dissapointed out of there. Want to get real-world feedback. Another thing, I am not sure how much daily electricity I would get around the area I plan to live. That's why the possible need for a planta.

Do you have a hold of such formula?
 

Rocky

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americanized said:
Thank you very much Rocky.

I am building a midsize house in the near future and I'm thinking of solutions to the eletricity problem. I am thinking of having two 3.6k Trace connected in parallel with a least 12 batteries to provide for my current needs. I spoked with a Trace rep down in Santiago in my last trip, but either she was not knowledgeable or was BSing me, talking about only a 4 hour run for such system. I came dissapointed out of there. Want to get real-world feedback. Another thing, I am not sure how much daily electricity I would get around the area I plan to live. That's why the possible need for a planta.

Do you have a hold of such formula?
There are many possibilities and it is likely that you will find that having both an inverter and a generator will cost you the least for the most service.
Nevertheless, I understand what you want to do, by having the two 3.6 inverters interlinked to give you 220 volts. At least I guess that's what you mean when you say you want the 2 units in parallel.
The amount of batteries is what decides how long you can go without power.
I have 24 batteries hooked up to a 3.6 Trace and can go an entire day operating everything except the fridges, hot water heater and water pump.
I do have low consumption bulbs and turn off unnecessary equipment during lenghty blackouts.
If I maxed out the inverter, using all I could without popping a breaker, I could run the batteries down in 6 to 8 hours.
Before even attempting to get into formulas, I would like to mention than I am not an electrician nor an engineer, however have had a fair bit of experience with this type of equipment over the last 14 years, fighting power failures.
If you do not have a generator to back up the inverter system, what do you do when you finally run the batteries down, other than sit in the dark, twiddling your thumbs and cursing the electric company, and Lord knows that if a hurricane ever knocks out the power for 5 days, you'll be going nuts.
So it really is an option to be looked at.
If you have a generator, you can go easier on the inverter & battery investment, as you have a second line of defense.
 

americanized

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I think my needs are more than 3.6k, closing to 6k at any given point. That's the reason for two units. The generator as a backup does not sound bad to me. Initial cost is not an issue. My concern is on going cost with the kind of (future) fueling cost in DR, at the rate they consume. I am also researching solar for charging inverter batteries during the day. Since I have some time to plan for all of this, I want to end up with the best solution I can.
 

Danny W

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americanized said:
I think my needs are more than 3.6k, closing to 6k at any given point. That's the reason for two units. The generator as a backup does not sound bad to me. Initial cost is not an issue. My concern is on going cost with the kind of (future) fueling cost in DR, at the rate they consume. I am also researching solar for charging inverter batteries during the day. Since I have some time to plan for all of this, I want to end up with the best solution I can.

Solar charger for inverter batteries sound interesting. That would just provide a small portion of the power needed, I assume. I know some people use solar powered pumps for their swimming pools. I'd love to know what practical applications are actually in use. Being off the grid seems a long way off. - F
 

Rocky

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Danny W said:
Solar charger for inverter batteries sound interesting. That would just provide a small portion of the power needed, I assume. I know some people use solar powered pumps for their swimming pools. I'd love to know what practical applications are actually in use. Being off the grid seems a long way off. - F
It's not difficult or all that expensive to be off the grid.
What's tough & costly is trying to live the same lifestyle, as if you were on the grid.
AC units, hot water tanks, fridges, water pumps and the like, are big power eaters and one has to look at special ways to circumvent the need.
 

MrMike

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americanized said:
I think my needs are more than 3.6k, closing to 6k at any given point. That's the reason for two units. The generator as a backup does not sound bad to me. Initial cost is not an issue. My concern is on going cost with the kind of (future) fueling cost in DR, at the rate they consume. I am also researching solar for charging inverter batteries during the day. Since I have some time to plan for all of this, I want to end up with the best solution I can.

Unless you are a millionaire you need to seriously consider adjusting your lifestyle to get your needs down around 2K maximum if you are planning on living in the DR.