How many solar cells to power my house?

Welcome to our community

Be a part of something great, join today!

Denny Crane

It's not even loaded!
Staff member
Administrator
Joined
May 24, 2007
Messages
73,114
Likes
10,945
Points
113
http://tlc.howstuffworks.com/home/question418.htm

A "typical home" in America can use either electricity or gas to provide heat -- heat for the house, the hot water, the clothes dryer and the stove/oven. If you were to power a house with solar electricity, you would certainly use gas appliances because solar electricity is so expensive. This means that what you would be powering with solar electricity are things like the refrigerator, the lights, the compute*r, the TV, stereo equipment, motors in things like furnace fans and the washer, etc. Let's say that all of those things average out to 600 watts on average. Over the course of 24 hours, you need 600 watts * 24 hours = 14,400 watt-hours per day.

From our calculations and assumptions abo*ve, we know that a solar panel can generate 70 milliwatts per square inch * 5 hours = 350 milliwatt hours per day. Therefore you need about 41,000 square inches of solar panel for the house. That's a solar panel that measures about 285 square feet (about 26 square meters). That would cost around $16,000 right now. Then, because the sun only shines part of the time, you would need to purchase a battery bank, an inverter, etc., and that often doubles the cost of the installation.

If you want to have a small room air conditioner in your bedroom, double everything.

Because solar electricity is so expensive, you would normally go to great lengths to reduce your electricity consumption. Instead of a desktop computer and a monitor you would use a laptop computer. You would use fluorescent lights instead of incandescent. You would use a small B&W TV instead of a large color set. You would get a small, extremely efficient refrigerator*. By doing these things you might be able to reduce your average power consumption to 100 watts. This would cut the size of your solar panel and its cost by a factor of 6, and this might bring it into the realm of possibility.

The thing to remember, however, is that 100 watts per hour purchased from the power grid would only cost about 24 cents a day right now, or $91 a year. That's why you don't see many solar houses unless they are in very remote locations. When it only costs about $100 a year to purchase power from the grid, it is hard to justify spending thousands of dollars on a solar system.
 
For yuks, I tried to figure out what it'd cost me to go solar for my house and whether it's worth it.

Browsing a few WWW sites, I see the cost for a solar system that powers a typical home is between $15,000 and $25,000 after uncle sam dumps a bunch of hard earned taxpayer money into it in the form of rebates and credits and so on.

So if I paid cash for it, and my bill is $150/mo, it'd take me 8.3 years to break even for the $15,000 system. But that's assuming I'd actually get 100% of my power from the solar panels, which I wouldn't. A lot of the companies selling solar panels and installation claim your goal should be 50%. So now it's looking more like 16.6 years to break even. Get a loan to pay for it, and it may never pay for itself...

The solar panels have a 25 year warranty. Neat. I assume that's their lifetime. So when you factor in the 40% of the cost the govt. is paying, it's a money losing proposition all the way around.

The really great idea is to make up for those losses with volume. Why lose $1,000 for a solar panel installation when you can lose $1,000 for each solar panel installation and do it en masse? No wonder the economy is failing.

I think I'll pass for now.
 
I love how people always put "hard earned" in there. When I was a TA at USC, my students, who were all idle rich children of entertainment types even used to refer to it as their "hard earned" money. I'm sure CEOs believe their multiple-million-dollar bonuses are "hard-earned" too.

Compared to the people who die in Bangladeshi garment factory disasters, no dollar in America is hard earned.
 
For yuks, I tried to figure out what it'd cost me to go solar for my house and whether it's worth it.

Browsing a few WWW sites, I see the cost for a solar system that powers a typical home is between $15,000 and $25,000 after uncle sam dumps a bunch of hard earned taxpayer money into it in the form of rebates and credits and so on.

So if I paid cash for it, and my bill is $150/mo, it'd take me 8.3 years to break even for the $15,000 system. But that's assuming I'd actually get 100% of my power from the solar panels, which I wouldn't. A lot of the companies selling solar panels and installation claim your goal should be 50%. So now it's looking more like 16.6 years to break even. Get a loan to pay for it, and it may never pay for itself...

The solar panels have a 25 year warranty. Neat. I assume that's their lifetime. So when you factor in the 40% of the cost the govt. is paying, it's a money losing proposition all the way around.

The really great idea is to make up for those losses with volume. Why lose $1,000 for a solar panel installation when you can lose $1,000 for each solar panel installation and do it en masse? No wonder the economy is failing.

I think I'll pass for now.

You're not factoring in the inevitable and continual inflation for gas or electric power. 8 years from now it will be double what it is now, and 16 years from now double-double, or 4 times what it is now.

You're also not factoring FREE solar power for the rest of your life once the equipment cost is recouped.

You're also not factoring in the option of selling your excess solar power to the local utility, which is a common way of helping to pay equipment costs.
 
I solared my house for 22k. It's a 6,000 watt system. My electric bill is .99 a month. I've fed the grid more than I consumed.

My electric bill was an average of $780 a month.
 
Lots of solar panels around where I live, both on homes and in the countryside. The home panels are usually limited to the amount of space on the roof so most are used to power hot water heaters and some but not all of the home appliances. They need to be used in combination with a green lifestyle with less appliances in the house, high efficiency, and stricter usage.

Question marks about the longevity of the coatings and materials used to construct the panels as well. Dust and pollution can cause them to degrade over time but as the panels keep getting replaced with newer designs, long-term testing being conducted on previous panels becomes less relevant.

Depending on where you live, home turbines could be a better solution, or in combination with panels can provide off-the-grid living (along with a well and septic tank).
 
Also, in before the "Al Gore airplane/mansion/tour bus" joke.
 
I love how people always put "hard earned" in there. When I was a TA at USC, my students, who were all idle rich children of entertainment types even used to refer to it as their "hard earned" money. I'm sure CEOs believe their multiple-million-dollar bonuses are "hard-earned" too.

Compared to the people who die in Bangladeshi garment factory disasters, no dollar in America is hard earned.

Yep, it's hard earned.

It's not taken at the point of a gun.

Oddly, my complaint is that poorer people are taxed to pay for the solar on rich peoples' homes. What's the point in that?
 
Solar panels are only $168 per panel. If one goes down; it only cost you that amount for that panel. You don't have to pay the entire $22k.

Also the battery isn't a good idea unless you are outside the grid. All you need is to make Edison enough energy to turn the clock back enough. What you use at night turns it back.
 
I'm not making this thread as a political statement. It's purely the economics of buying a system for my house, and what I learned from reading up on it.

I don't want a "green" lifestyle. I want to put air conditioning in my bedroom and was hoping solar would be an economical way to pay to power it. It's not.
 
I'm not making this thread as a political statement. It's purely the economics of buying a system for my house, and what I learned from reading up on it.

I don't want a "green" lifestyle. I want to put air conditioning in my bedroom and was hoping solar would be an economical way to pay to power it. It's not.

Depends where you live. I have blaring sun and 100+ weather. Solar panels easily pay for itself
 
My Parents just paid 4k after reimbursements for there 8 solar panels on their house. Their Bill went from 288 a month to 75 and it hasn't been that sunny around Portland until recently. I guess it just depends on how much you pay for the panels and how much your bill is on if you want it or not.
 
Oil will become more scarce until the world can't find any more. So the cost of oil will increase until we run out. Even if costs of alternative energies don't fall, they will become cheaper relative to oil. As the price of oil rises above the price of alternatives, the alternatives will become more popular than oil.

So Denny, the positive talk about solar power isn't about right now. It's about what's going to happen in a generation, in our lifetimes.
 
To go along with what Denny is saying that it's important to point out that solar cell technology will never either increase in efficiency and/or go down in cost.

Also it's important to mention that under the theory of abiotic oil the earth will never run out of oil while the sun will eventually burn out.

Solar cells are the betamax of energy technology.
 
I solared my house for 22k. It's a 6,000 watt system. My electric bill is .99 a month. I've fed the grid more than I consumed.

My electric bill was an average of $780 a month.

The numbers don't look realistic.

For $780/month, you should have been buying at least 2x 6000 watts (144 kWh @ $.09 per)
 
The numbers don't look realistic.

For $780/month, you should have been buying at least 2x 6000 watts (144 kWh @ $.09 per)

All I know is I have 50 panels on my house. I have two inverters to go along with the system. Tomorrow, I will look outside.
 
Well that sucks! I wish I got them!

You did. The price of your solar panels would have been much higher. Price divided by hours is what you pay for your electricity, so it's a discount.
 
All I know is I have 50 panels on my house. I have two inverters to go along with the system. Tomorrow, I will look outside.

Here's my math, feel free to correct it (anyone).

6000 watts * 24 / 1000 = 144 kwh
144 kwh * $.09/kwh = $12.96
$12.86 * 365 days / 12 months = $394.20

Or almost exactly 1/2 what you say your $780 bill was

So it would seem you're using less than 1/2 the electricity you did (and enough less to contribute back to the grid). Or your bill isn't really $.99 like you say.

Here in Southern California, you have to pay $20 minimum to the electric company even if you use zero electricity. I have a neighbor who built a new home with solar and told me there's no way to avoid paying at least the $20.
 
Here's my math, feel free to correct it (anyone).

6000 watts * 24 / 1000 = 144 kwh
144 kwh * $.09/kwh = $12.96
$12.86 * 365 days / 12 months = $394.20

Or almost exactly 1/2 what you say your $780 bill was

So it would seem you're using less than 1/2 the electricity you did (and enough less to contribute back to the grid). Or your bill isn't really $.99 like you say.

Here in Southern California, you have to pay $20 minimum to the electric company even if you use zero electricity. I have a neighbor who built a new home with solar and told me there's no way to avoid paying at least the $20.

You are right!!!!

ImageUploadedByTapatalk1367811185.445543.jpg

And I saw that its 50 panels x 250 watts = 12,500 watts
 
It looks to me like a single solar panel generates 80 watts in direct sun. 50 panels would be 4000 watts.

4000 watts is enough power for 40 x 100 watt light bulbs, or 10 computers, or a moderate sized central air conditioning system, etc. A refrigerator uses about 1400 watts.

The solar panels only work in the daylight, so you must be paying for electricity from the electric company for as many as 16 hours a day. Granted, you are paying for that power when your A/C doesn't need to work as hard, etc.
 

Users who are viewing this thread

Back
Top