Dollar for dollar, hot water solar collectors are your best investment. Hot water collectors are far more efficient than photovoltaic panels at turning the suns energy into a useable form of energy in your home. You can get into a solar system that can generate enough hot water for a family of 4 for around $3000 in my location. I am considering this on my own home. I am a so-called right wing denier, but when it makes financial sense and can "indisputably" help the environment, how can I, or anyone be against it.

I would point out however, the amount of solar radiation available in Southern California, as in this example, has considerable more radiation(kWh/m2/day) than the majority of the US. Not sure if this is done to paint a more idealistic picture or not, but people living in areas furter North will need more collectors, hence more money.

I agree solar is the way to go. Even up here in Northern NH there are homes that benefit from solar. The technology has come a long way from the old days of solar power. If it's good enough for NASA it should be good enough for all. I also think wind farms are also in the future.

Hey, we pat ourselves on being such a technological species so why not put our money where our big fat mouths are? Oh sorry we are much too busy killing each other for senseless reasons to apply and knowledge for good. My bad.

I'm sorry but I cannot for the life of me figure out how you can power a house on a scant 4kw (or even 6 kw) of solar power. Most people see the 4kw and think that that is more than enough. It doesn't even come close if you want to be able to live as easily and with all of the comfort that we're used to.

The problem isn't the 4kw of power. It's 4 kw at 15.4+/- volts. That 4kw at 15.4 volts turns into a mere 513 watts at 120 volts. Enough for a few lights and a TV.

In order to make a true 4kw at 120 volt system (still not really enough but we'll use it as an example) you'll have to spend 7.8 times what these people did. It would take a long, long time to pay back a $280,800 investment. You'll also need a good bit of real estate to put all of those panels on.

Until we're bent over backwards and people are fighting in the streets over food and water the governments of the world and private industry are only going to give lip service to solar power and the enviroment in general.

It will probably take the combined efforts of the entire science community to come up with a cheap, economical solar power solution. We will do it but don't look for it as long as barrels of oil and train loads of coal are coming out of the ground

Michael:

I'll let the silly, non-topical comment on killing each other for senseless reasons slide.

But the NASA comment is downright funny. The great thing about solar cells is they work well when there are no things called "clouds" in the way. Your right, solar has come a long way and it will probably at some point be even better, but right now, it is not a great choice to meet our present power needs. Check with Ted Kennedy on the wind farm thing.

Say, can you inform us interested bloggers how many KW of solar power you have provided for your home?

Richard is right on the money and well put.

Here is a good article on proposed solar farms to be built in the Southern California deserts.

http://www.wired.com/science/planetearth/news/2005/11/69528

I think this is a great idea but it certainly isn't going to be a save all from our reliance on conventional sources of energy. My concern is what the potential environmental impact would be for using vast tracts of the desert for solar farms such as this. There are certainly going to be those who will ask that question. I'm also thinking that there may be issues of whether they create "hot spots" and thus contribute to global warming.

The problem isn't the 4kw of power. It's 4 kw at 15.4+/- volts. That 4kw at 15.4 volts turns into a mere 513 watts at 120 volts. Enough for a few lights and a TV.

Richard, can you say a little bit more about this? It's been too many years since I did power calculations as a working EE, but I think I still remember the basics, and I think you're mistaken about the "513 watts at 120v" -- I think it's 4kw, whatever the voltage.

A "kw" is unit of power -- current * voltage in this context. The power is the same, whatever the voltage. 4kw at 15.4 volts corresponds to 260a. The same 4kw at 120V corresponds to 33A.

The homeowner needs an inverter to convert the low-voltage high-current solar panel output to "regular" 60hz 120V ac power. The inverter wastes up to about 15% of the available power.

As a comparison point, a modern residential service today provides 200A service at 120v.

That's about 24kw, or about six times the figure quoted in the thread-starter.

If the average home only requires 4kw, then the average home doesn't require 200A service, though I suppose the idea is to provide capacity for instantaneous high-current needs of short duration.

In any case, unless I seriously misunderstand something, 4kw is 4kw -- regardless of the form in which that power is distributed throughout the home.

BT,

You are correct, 4kw is 4kw regardless of the voltage. You are also correct in the theory of inital loads accounting for the higher 200amp service. I will agree with Richard in theory however. The 33 amps @ 120V is not nearly enough to power a home unless they are living in the dark ages. I would not try anything less than 100 amps to barely get by. Most homes built 40+ years ago usually had 100 amp services. Most have upgraded services to 200 amp now as 100 amps is not enough. When you combine your big power users such as wells, stoves, mcirowaves, Air-conditioners, dryers, etc., this number would fall way short. I have a 4500 Watt continuos generator for power outages and I have to run only the bare necessities or I run out of power. So I would put the estimate more at 3X what this article says. Again, I would state that this location has considerably more solar energy avaiable than most of the US. So anyone North of this location would need more panel area yet.
So one would be looking at a minimum of $108,000 investment and still could fall short of power depending on what they have for appliances. If anyone wants to seriously consider solar, look into domestic hot water and possibly use a heat exchanger to offset heating cost during the Winter. The efficiency is far better in hot water solar collectors. The numbers just don't back up the photovoltaic systems with current efficiencies.

Engineer types - It's been 20+ years since the last time I studied electricity, so your thoughts on this subject are much appreciated. Everything I've read about solar seems to indicate that a good-size home can manage on 4 kw of solar panels. Check out the Maine solar house: http://www.solarhouse.com/index2.htm and click the solar power link, that gives some details on the inverters they use to power their 2900 square-foot home from 4.2 kw of solar panels.

Laura,

Thank you for the link. I believe that they are painting a rosey picture of their power useage. Could you live on 4kW of power? Sure, you could live without any power, but at what comfort level are you willing to go down to. Anyone who uses a standard 4.5kW gas generator at times for emergency power will tell you what an inconvienence it can be. You really have to watch what you are using and when. I suppose that they could have all L.P or natural gas dryers, stoves,etc which isn't that uncommon. Still if you throw an air-conditioner or microwave into the mix, you are out of power. I did not see anywhere on their site a list of appliances that they use in their house and the power useage, maybe I missed it. Looking at this from a financial standpoint, I can't see the payoff for a long, long time if done correctly. Now if they have a bank of batteries for storage and were not home for 8 - 10 hours/day, it might work. I don't believe this is their case as they still have too small of an inverter to carry enough amps at 120/230V into their house. Batteries will add more cost yet to the house and require maintenance and have a limited life. I do like their useage of the hot water solar panels though, floor heat is great and their storage tank has enough volume to carry them a day or so without the sun. I think from that side of the project, they have a winner.

I think the key here is to appreciate the difference between "peak" and "average" load. A viable power supply has to handle both.

We've talked about New Hampshire. According to this report from the US Dept of Energy, the average annual per-capita electricity consumption in New Hampshire for 2001 was 3,009 KWatt-hours. If we assume about six people per household (just my guess), that's about 18,000 kwatt-hours per household. There are 8,760 hours in a year. I divide 18,000 by 8,760 and I get about 2kwatts.

Thus, I think the estimate of 4-6kwatt average power consumption for a typical household seems to be at least within an order of magnitude and perhaps even a factor of two of the right answer.

I think that mc's concerns reflect the instantaneous, or surge, demand. I think this means that the energy storage mechanism needs to be able to handle a 4-6kwatt average load, and also needs to handle a 200A short-term surge.

I think this has more impact on the design of the inverter, service design, and house wiring than the collectors themselves. Most residential systems are designed to pull power from the grid when needed anyway (and sell excess power to the grid when not needed, by the way).

All in all, I think the information provided in the threadstarter is reasonably accurate, and I think mc's concern about peak load are well-taken.

BT - Yes, from what I understand most states allow "net metering" - that is, they're connected to the grid and draw power as needed, and also can sell power back to the grid if they produce a surplus. That's the case with the Maine solar house, which does not use any sort of battery storage of electricity. They claim they end up with a net-positive electrical supply per year, and only pay to be connected to the grid. Interesting stuff.

Part of the costs of doing the full solar conversion includes dumping the great EnergyStar rated appliances for something really efficient. If you wanted to be serious about going solar, then rebuilding would be your best option.

In any case, a 4-6kw system has a relatively small footprint and with the sell back to the grid you can avoid the extra expenses of a lot of the classical solar electric power systems (like batteries).

Well, 5 days after my post and no reply regarding the amount of KW solar power provided for the AGW proponents homes. Wonder why that is?

This is a nice scientific debate over how these systems work and all but let's just face the reality of the world shall we? Residential solar systems cost too much, require too much maintenance, and are frankly too inefficient to power the average home. Only those people who have an excess of money (who really has that) and the true desire to live a reduced lifestyle (Ed Begley comes to mind), could put those systems into action. The rest of us will need to wait for better advancements in technology. But hey, you want to spend your money on it, knock yourself out, that means just more real power for the rest of us.

Well, 5 days after my post and no reply regarding the amount of KW solar power provided for the AGW proponents homes. Wonder why that is?

Because it's a cheap shot ad-hominem that only inflames an argument and offers NO constructive insight. The kind of tiresome cheap shot that makes discussion more, rather than less, difficult.

Oh, and in my case it's because I don't own my home. The building I live in is in an urban setting with a 100 year old slate roof. Solar power for individual homes is not an option for the overwhelming majority of urban residents like me.

Darren, there are a great many factors involved in determining the KW load for a house and each is an individual case. Guess what, we haven't even begun to talk solar yet.

There are also too many factors involved in making a decision to go solar that depend on how much capital you have to spend and at what stage. For example, to try to put in a full solar kit (or even the partial one without batteries) on my current home would be absolutely insane. The house is laid out the wrong way, built of the wrong materials and has some bad design features from a solar point of view. The cost to "go solar" other than in a way to help the load during the day (and adding in hot water) would be way more than it was worth.

OTOH, if a fire took the place out, I could afford to rebuild from scratch using different materials and methods from the standard "slap it up quick" contractor methods and "convential wisdom" on laying out of houses.

If you want to look at it this way, building with cheaparse materials using cheaparse methods by century old ideas of homebuilding makes for seriously ups the costs of any modification, not just solar. Great example of cheap: Blown Insulation. Could be decent stuff, but the usual stick the hose in the attic and let it come down where it may is a waste of time and money, but it counts as "insulation".

Kamatu

I really don't understand your logic with not going solar. Regardless of the age of the house and lesser efficiencies, heat and electricty are still present whatever the age of the house. Regardless of how quick energy goes out, you are still paying for it. Solar power would still allow you to offset your cost if you believe enough in it. Actually, your payoff would be quicker on a less efficient house than a newer one. A solar hot water system can be modified easily to fit any house(unless poor sunlight exposure) and anyone can gain from this system at a relatively low cost.

If you are comparing todays houses to century old homes and say that there has been no major innovations on even the most basic spec homes, you don't understand construction at all. Cellulose "blown in" insulation is fantastic at insulating and enviromentalist should love it since it is all recycled paper. Any insulation company can lay this stuff in relatively accuratly and the homeowner can always have them add in more than stnadard for extra R values at minimal cost. It's very cheap. I don't even know where to start with the rest of the construction process(insulated PEX water lines, blown in wall insulation, polyurethane spray foam, triple pane windows with argon gas, house wrap, high r value fiberglass exterior doors, etc, etc. So as you can see, if you look below the surface of new homes, there are tons of efficient break-throughs in construcion practices and materials.