Your comment appears to be unrelated to Pakistan and, due to the confusion of units, has been reduced to nonsense. Moreover, your implied calculations don't work out.
If we assume that you meant €7000 for 6 kilowatts peak (not 6 kelvin wurtzite henries or 6 kilowatt hours, neither of which is sensible) the probable answer is that your relative paid 25× the current market price for their solar panels and therefore got 25× the payback time. However, if we assume €0.12/kWh and a 20% capacity factor, 6 kilowatts peak would average 1.2 kilowatts, which is 10520 kWh per year, which works out to €1260 per year, which would be a payback time of 6 years, not 15 years.
Moreover, another way of saying that the payback time on a durable investment is 15 years is that the investment returns 6.7% per year. That would be a highly profitable investment, even without government subsidies.
sorry yes. He told me, installation is 6,000 W and is about 91% efficient at peak. 12 460W panels. panels point in optimal direction. In spain he sells excess to grid at €0.04 per KHW. Lowest cost of importing is €0.085 for KHW at night, about €0.22 at peak hours. He ran the numbers on power not bought (self consumption) + power sold, over a year. He said it comes to about €500 for the year. He added this really surprised him and he started asking around, and this seems to be typical for rooftop solar in the Canarias.
That's a 7% yearly ROI, which is a pretty decent number, better than you'd do on average in the stock market and more predictable. If he had a little storage so he didn't have to sell any, it would improve further. But also 6000W of panels in the low-cost category now costs €300: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis...
You need more information to calculate the ROI. I gave you the peak efficiency, Which comes from clean panels and no clouds. The average efficiency is closer to 70%. While the canaries are pretty sunny, the panels get dirty very quickly (fine dust from Sahara), Actually, if you count cleaning costs, the ROI goes down even more. And also consumptions is at its peak in the evening when there is no sun. He was thinking about getting storage, A Tesla Powerwall 3 installed is about €11,000, No way that is worth it. My impression is that places where ROI is much better is also places where you get more than €0.04 per KWH.
That isn't the efficiency, which is a number somewhere under 23%, dividing the number of joules of light into the panel by the number of joules of electrical power out of it. Maybe you mean that at peak he gets 91% of the advertised 6kW, i.e., 5500W?
Anyway, you said they paid €7000 and get back €500 per year, which is enough to calculate the ROI at 7.1% per year.
Powerwalls are indeed extremely overpriced. But battery prices are down to below US$70/kWh (US$19/MJ, €17/MJ); if we assume the maximum production in a day is about 25%, that's 36 kWh (130MJ), so it would be about US$2500 for that amount of battery. But probably even €500 of battery (7.2kWh) would make a big dent. That would be 1800 watts for four hours in the evening.
Depending on the type of evening consumption, it might be possible to ameliorate it dramatically with various kinds of thermal storage, or even plugging the washing machine into a timer. Those are much cheaper than batteries.
yes 7% ROI if no depreciation, but neither panels nor inverter are expected to last much beyond ten years. I was actually chatting with him just now since I got into this discussion, and he said he also needs a maintenance/emergency callout and cleaning contract, thats about €250 a year. In spite of this, he was still happy with doing this, good for the planet, even if not for this wallet. He also put up a large screen with the relevant numbers to train others in the house to use appliances at optimal times.
Panels are normally warranted not to drop below 80% of rated output after 25 or 30 years, although some are defective and crack within a year or so. But they don't start dropping off more rapidly at that point; rather, their output declines more slowly after that point. Those panels will be fine 50 years from now if he doesn't throw them away.
Inverters are a different problem, and they do in fact die after a few years. But you don't need the inverter to use the energy.
A twenty-foot container, I imagine? Retail for onesies seems to be about 4× that.
Typically panels account for about a third of the cost of a turnkey solar power system, but that's largely because of historical design features that are no longer necessary.
Or someone who lurks here, but never posts. Not everybody has an account here. I was just curious because I was talking my friend who has the solar just earlier today and he was a bit upset when he ran the numbers.
If we assume that you meant €7000 for 6 kilowatts peak (not 6 kelvin wurtzite henries or 6 kilowatt hours, neither of which is sensible) the probable answer is that your relative paid 25× the current market price for their solar panels and therefore got 25× the payback time. However, if we assume €0.12/kWh and a 20% capacity factor, 6 kilowatts peak would average 1.2 kilowatts, which is 10520 kWh per year, which works out to €1260 per year, which would be a payback time of 6 years, not 15 years.
Moreover, another way of saying that the payback time on a durable investment is 15 years is that the investment returns 6.7% per year. That would be a highly profitable investment, even without government subsidies.