Newbie from Philippines with a 300W setup

[ILFE]

[SunEagle]

Okey so previously without solar I was consuming an average of 300kWh per month.
It follows that being connected to the grid alone, I'm consuming 3,600kWh per year.
The power company charges for about $0.23 per kWh so total for the year is $828.

Now given that my total setup is $1,600
After setting up a solar battery system I'm consuming an average of 175kWh per month from the power company.
Which could mean I'm producing an average of 125kWh per month so in a year it's 1,500kWh average a year.

So $1,600 divide by 1,500kWh is $1.06 per kWh. This is the power cost of the new solar battery setup per kWh.
Compared with the POCO cost, my solar battery setup actually costing me $0.83 more.

Now how many years until I get ROI of $1,600? And how long my batteries would last? I don't know yet.
Let's say my batteries will only last for 2 years. And 2 sets of 100h Motolite truck batteries at $136 each or $272 for two.

Let's say cost from POCO is $0.23 multiplied by average 125kWh produced a month is $28.75. So in a year it is $345.
Theoretically, the ROI would be $1,600 divided by $345per year is 4.63 years.

But then again, I have to replace the batteries every two years so let's add three sets of $272 for a total of $816. This brings my total cost to a whooping $2,416

So let's recompute: $2,416 divided by $345 per year is about 7 years and 2 months.

It's like getting mortgage of a house that's payable in 7 years. And after the 7 years, you have no more obligation to the bank. The house is all yours.

So by year 8, you only have to buy batteries for $272 for two or maybe but that time with the current trend of technology the cost batteries either goes down or up. So let's stick with $272 for two.

So by year 8, you will have $272 divided by cost from POCO of $345 per year is about 9 months and 15 days. And the rest of the months until the year 10 is your savings. And the cost of my solar battery system during the year 8 is only costing me $0.18 per kWh ($272 divide by 1,500kWh per year). But on year 9, it's not costing me anything since the $272 is already paid for during the year 8, and so will be the odd numbered years after year 8.

Given that the cost of batteries will go up, so does the power cost of the power company. This year alone the cost of power from POCO is now about $0.26 how much more in 7 to 8 years.

Solar panels will last 20 to 25 years but after that, the solar panels' current efficiency will only be 90% down to 80% but still can be used. After 20 to 25 years, how much would you think the cost of solar panels will be?

So does this prove that having a solar battery setup is achievable in terms of total ROI? Or I'm just dreaming?

And if I do just dream: bragging I have electric power, helping your neighbors charge up their cellphones or gadgets in case of emergencies, watching TV, listening to music, cooling down when everyone around you is cursing the long brownout is still priceless for me.

Well actually you are using the wrong formula. As of now it seems that your battery system is producing about 125kWh / mth but that is based on your current use and historical use and not necessarily what your batteries are generating.

To determine the actual amount of kWh your system can produce you use the battery Ah rating x voltage x % of discharge.

So if your system is say 600Ah at 12volts and you discharge it daily about 25% your usage would be 600 x 12 x .25 = 1.8kWh per day. Or about 54kWh per month which is saving you about (54kWh x $0.23/kWh = $12.42) or about $150/yr. If you use more than 25% of the battery capacity per day then your output is higher but you also start to shorten the lifespan of the battery and will have to replace it sooner. At that $150/yr savings and the need to replace the batteries every couple of years will come to a payback way more than 10 years.

Now if you reduce your usage (tell your cousin it just hot and deal with it. LOL) then your solar battery system can start to save you a larger portion of your usage but it will still take a while to pay for itself.