# How many using solar power?



## pauldavidmena (Feb 4, 2013)

Given that many parts of Mexico experience 300-plus days of sunshine per year, solar power seems a very sensible option. My question is: how many on this forum are using it? This includes both those living off the grid and those using it to supplement their utility-provided power.


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## cuerna1 (Mar 7, 2015)

pauldavidmena said:


> Given that many parts of Mexico experience 300-plus days of sunshine per year, solar power seems a very sensible option. My question is: how many on this forum are using it? This includes both those living off the grid and those using it to supplement their utility-provided power.


We've had a PV system for perhaps the last 8 months. Have a bi-directional meter with CFE. Every bi-monthly bill so far has been for 52 pesos (26 / month) (which is their admin fee) and our credit kwh balance is growing. At this point we would have been in DAC. Should pay for itself in like 6 years or so.


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## maesonna (Jun 10, 2008)

A friend in Guadalajara (city) reports that he has just received his first bill after going solar. It was a few hundred pesos. Pre-solar, he says, his bills were in the high 2000's. I don't know any more details about his installation.


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## pauldavidmena (Feb 4, 2013)

@cuerna1 - thanks for the quick reply. Not being the overly adventurous type, I'd probably opt for a bi-directional system versus living entirely off the grid. Much of it, however, would depend upon whether we build on our own when the time comes, or purchase an existing home.


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## TundraGreen (Jul 15, 2010)

pauldavidmena said:


> Given that many parts of Mexico experience 300-plus days of sunshine per year, solar power seems a very sensible option. My question is: how many on this forum are using it? This includes both those living off the grid and those using it to supplement their utility-provided power.


I use solar for hot water. I am planning to rewire my house soon and will add solar electric in the process. Neither makes sense for me cost wise, since I use little gas or electricity anyway. I don't expect to live long enough for the gas and electricity savings to equal the installation cost. But I like the idea of renewable resources.


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## cuerna1 (Mar 7, 2015)

pauldavidmena said:


> @cuerna1 - thanks for the quick reply. Not being the overly adventurous type, I'd probably opt for a bi-directional system versus living entirely off the grid. Much of it, however, would depend upon whether we build on our own when the time comes, or purchase an existing home.


We never really considered the off-the-grid option. For one thing I'm not sure we would want the batteries etc that would require. And - while there is a lot of sunshine during most of the year - there is also a rainy season. Our installation is a little 'special' in that we have perhaps a 50+ foot tall wall on the south end of the property which borders on farmland. We dangled our panels off that wall. Tons of sun.


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## pauldavidmena (Feb 4, 2013)

@TundraGreen - I've heard that it can take 5 to 7 years to recoup one's investment, so it's good to point out one's motivation: whether it's about "being green" or saving green. For me, it's a combination of both: when solar energy is in such abundant supply in BCS, why not take advantage of it, while also making less of an impact on the environment?


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## TundraGreen (Jul 15, 2010)

pauldavidmena said:


> @TundraGreen - I've heard that it can take 5 to 7 years to recoup one's investment, so it's good to point out one's motivation: whether it's about "being green" or saving green. For me, it's a combination of both: when solar energy is in such abundant supply in BCS, why not take advantage of it, while also making less of an impact on the environment?


The length of time to recover the investment depends entirely on your usage; a general rule of thumb is meangingless, unless it happens to be calculated for your usage.

Before I put in the solar hot water heater, I used one gas cylinder every four months. Now the cylinders last 5 months. So my gas cost before was $100 pesos/month and now it is $80 pesos/month, saving $20 pesos/month. The system cost about $10,000 pesos to purchase and install. At a savings of $20/month, I will recover my cost in about 40 years.

My situation for electric is similar. my average bimonthly bill is $150 pesos. With the system my bill likely drop to the minimum, $52 pesos/bimonthly. That is a savings of $50/month. I am not sure what the current cost of panels is. If memory serves me correctly, I was quoted a price of around $15,000 each for the two panels I estimated I would need. if that is correct, $30,000 cost divided by $50 savings/month gives a pay back time of about 50 years.

There are some compensating advantages of the solar systems. Before putting in the solar hot water system, I had an old water heater that had to be lit every time I want hot water; it had no thermostat and could not be left on. Now I just have hot water and don't have to think about it.

Similarly, solar electric may have its advantages. Power interruptions are pretty common in my neighborhood. With solar electric, I will be immune to them during peak sun hours at least.


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## RVGRINGO (May 16, 2007)

TundraGreen said:


> ........
> Similarly, solar electric may have its advantages. Power interruptions are pretty common in my neighborhood. With solar electric, I will be immune to them during peak sun hours at least.


Actually, you would still be without power, as the solar panels feed the CFE grid, running your meter backwards, and do not feed your needs directly. To do that, you would need a controller system and a bank of batteries of sufficient capacity to feed your home through an inverter, producing 110v from 12V. That would even work at night or on cloudy days. 
With most solar panel systems, you still use CFE, mostly in the evening, and pay them back in the sunny daytime. Any excess you use builds credit, which they do not pay for in cash; just kilowatts.


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## TundraGreen (Jul 15, 2010)

RVGRINGO said:


> Actually, you would still be without power, as the solar panels feed the CFE grid, running your meter backwards, and do not feed your needs directly. To do that, you would need a controller system and a bank of batteries of sufficient capacity to feed your home through an inverter, producing 110v from 12V. That would even work at night or on cloudy days.
> With most solar panel systems, you still use CFE, mostly in the evening, and pay them back in the sunny daytime. Any excess you use builds credit, which they do not pay for in cash; just kilowatts.


Good point. I guess I didn't understand the connection. I know that without a bank of batteries, you cannot be independent of the grid. But I didn't understand how you need CFE power at times when the meter is running backwards, i.e. when you are generating more than your usage.

I just read about how the grid-tie inverters work. I see that they shut down when the grid is off.
https://en.wikipedia.org/wiki/Grid-tie_inverter


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## cuerna1 (Mar 7, 2015)

TundraGreen said:


> Good point. I guess I didn't understand the connection. I know that without a bank of batteries, you cannot be independent of the grid. But I didn't understand how you need CFE power at times when the meter is running backwards, i.e. when you are generating more than your usage.
> 
> I just read about how the grid-tie inverters work. I see that they shut down when the grid is off.
> https://en.wikipedia.org/wiki/Grid-tie_inverter


I guess the meter never really runs backwards - rather if the demand can be met by the current panel production - great - otherwise pull from CFE. Under the covers - so to speak - unused production will flow back to CFE.


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## sparks (Jun 17, 2007)

I have a black tinaco that produces plenty of hot/warm water from now until November. That is all I need for showers and I don't use hot/warm water to wash clothes or dishes. Just turned the boiler off for the next 6+ months

With CFE bills of 450 pesos for 2 winter months or 600 in summer, it's pretty hard to pay 3-4kus to install a real solar system of any sort


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## TundraGreen (Jul 15, 2010)

cuerna1 said:


> I guess the meter never really runs backwards - rather if the demand can be met by the current panel production - great - otherwise pull from CFE. Under the covers - so to speak - unused production will flow back to CFE.


As I understand it the meter really does run backward. But when CFE is off-line, the inverter has no frequency to synchronize with. Also, apparently, the inverters shut off for safety when there is no grid power. If CFE turns the power off to work on the lines, it would not be good to have a lot of solar panels pumping current into the lines.


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## cuerna1 (Mar 7, 2015)

TundraGreen said:


> As I understand it the meter really does run backward. But when CFE is off-line, the inverter has no frequency to synchronize with. Also, apparently, the inverters shut off for safety when there is no grid power. If CFE turns the power off to work on the lines, it would not be good to have a lot of solar panels pumping current into the lines.


Yes the inverter does go into some sort of hibernate state when CFE is not on.

Our bi-directional meter is digital and reports kwh consumed (taken from CFE) and kwh produced (sent to CFE). The inverter reports Total kwh produced for various periods. The difference between the inverter's number and the meter's number is what was consumed locally (demand our panels met without needing to pull from CFE).

btw - before we installed our system we had 3 - old fashioned meters with the spinning dials. CFE came and did a survey and declared that our meters were 'slow' and were under-reporting something like 20% of our usage. They wanted to replace our meters at that time. Gosh we were about to enter DAC with the old meters ! That is something else which helped us make our decision.


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