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# Switching To Solar Power – One Month Later

730

If you wanted to be a crotchety bitch, which clearly you did, you would have mentioned that it'll take him roughly 11-15 years to recoup his investment of $40,000 for the equipment and setup. That's what I'd go with. ### Re:Wait to winter time when there is less sun to s (1) #### Narpak (961733) | about 6 years ago | (#24282907) If you wanted to be a crotchety bitch, which clearly you did, you would have mentioned that it'll take him roughly 11-15 years to recoup his investment of$40,000 for the equipment and setup. That's what I'd go with.

Unless of course the price of energy rises significantly, then he will probably "recoup his investment" quicker. Not to mention that he is less dependant on energy companies and that the effectiveness of solar panels is bound to increase. As mentioned in this earlier Slashdot post:
http://web.mit.edu/newsoffice/2008/solarcells-0710.html [mit.edu]
http://hardware.slashdot.org/article.pl?sid=08/07/11/2017237 [slashdot.org]

Even if solar panels only reduces your energy consumption during the summer; if everyone in a relevant area did this perhaps the general price of energy would drop; even during winter. Since the general consumption would be reduced.

### Re:Wait to winter time when there is less sun to s (3, Informative)

#### Rei (128717) | about 6 years ago | (#24282983)

Working against that, you need to amortize your capital costs and pay for maintenance. Still, in some parts of the country, solar can indeed give you a reasonable mortgage length and IRR [daughtersoftiresias.org]

### Re:Wait to winter time when there is less sun to s (1)

#### mattack2 (1165421) | about 6 years ago | (#24282899)

Not cost effective? He went from a $348 bill to a$11 bill.. It will go down in the winter of course, as you say. But it will "pay for itself" in a short period of time.

### Re:Wait to winter time when there is less sun to s (2, Interesting)

#### RobinH (124750) | about 6 years ago | (#24282359)

This is actually quite striking. I worked on a solar/wind project last year and the solar panel we were using was an 80W rated panel (normally provides a little over 60W in full sunlight at these latitudes), but I never realized how much your eyes compensate for the variation in illumination levels. When it was cloudy in the winter, even when you could see perfectly well and thought it was rather bright outside, the solar panel was only pumping out about 2 or 3 watts.

The idea is that it tends to be windy and sunny alternately, which is somewhat true, so they market wind and solar as a good combo, but the fact is the amount you have to spend to get the same power from wind is way more than the equivalent amount for solar, and trust me there are lots of times when it was calm and overcast for weeks.

Still I think the most economical setup would be to find a way to reduce the hardware as much as possible. Let's say you have air conditioning for instance. Take a solar panel, use it to charge a single 12V auto battery, and then use a voltage sensitive relay to turn on a surplus 12V marine air conditioner. Basically the solar charges up the battery. When there's enough power in there, the air conditioner kicks on and runs for 15 minutes or so and drains the charge out of the battery. The sunnier it is, the more the air conditioner runs, and that means your central air (powered by the grid) runs less. The benefit is that you don't need to fuss with inverters and big battery packs.

### Re:Wait to winter time when there is less sun to s (1)

#### shaitand (626655) | about 6 years ago | (#24282489)

That would be a nice idea if marine a/c units weren't ungodly expensive.

### Re:Wait to winter time when there is less sun to s (1)

#### Joe The Dragon (967727) | about 6 years ago | (#24282581)

There was this one guy who rigged up a window unit ac in his truck useing a 12Vdc to 120Vac inverter.

### Re:Wait to winter time when there is less sun to s (1)

#### shaitand (626655) | about 6 years ago | (#24282617)

a number of people do that here in florida if a hurricane knocks out power. A lot more plug A/C units into gas generators which are basically the same thing without the truck.

### Re:Wait to winter time when there is less sun to s (1)

#### maxume (22995) | about 6 years ago | (#24282935)

I think he means that the A/C was installed _in_ the truck, not hooked up to run off of power from the truck.

### Re:Wait to winter time when there is less sun to s (0)

#### Anonymous Coward | about 6 years ago | (#24282433)

As opposed to saving nothing at all??

### Re:Wait to winter time when there is less sun to s (2, Interesting)

#### Anonymous Coward | about 6 years ago | (#24282491)

Mod parent up! I am posting from a house with four 80W solar panels on a rainy day and the generator is on. If you want to go solar you need a lot of batteries and a lot of panels.
Of course, we don't have the convenience of mains power at all.

F.Y.I
Current usage is; 1 laptop (80W), 1 low power fridge (120W), 1 one modem (8W). Storage is 4 deep cycle batteries.

### Re:Wait to winter time when there is less sun to s (0)

#### Anonymous Coward | about 6 years ago | (#24282833)

What are you using for an ISP if you have no connections?

### Winter MegaHurtz (0)

#### Anonymous Coward | about 6 years ago | (#24282265)

I want to see what happens to usage in winter! When buns are a cold and Mhz use increases due to rainy days!

### Re:Winter MegaHurtz (2, Funny)

#### smitty_one_each (243267) | about 6 years ago | (#24282631)

It's OK, he has Three Dog Night on the iPod.

### Re:Not a month (1)

the summary never mentioned the time period of the bill... and you apparently stopped reading TFA after that paragraph... he estimated his monthly (30 day) bill to be about $16 ### Re:Not a month (1) #### krkhan (1071096) | about 6 years ago | (#24282497) the summary never mentioned the time period of the bill... and you apparently stopped reading TFA after that paragraph... he estimated his monthly (30 day) bill to be about$16

For your later point, he did. For the former: RTFS and then RTPP.

Loyd Case at ExtremeTech has written a follow-up after about a month of normal use.

I just pointed out that he didn't use it for a month after-all. The estimate surely is handsome but that still doesn't vindicate the summary's inaccuracy.

### That last paragraph says it all (3, Insightful)

#### WindBourne (631190) | about 6 years ago | (#24282393)

money going towards assets rather than a simple debt. Would you rather own or rent?

### Re:That last paragraph says it all (3, Informative)

#### raoulortega (306691) | about 6 years ago | (#24282537)

Depends on how fast those assets depreciate, and the long-term maintenance costs.

### Re:Eh (3, Interesting)

So he saved about $330/month. It cost him$36K (which really cost $50K, but let's say). So it'll take 109 months to get back the money, or 9 years, not adjusting for inflation and investment opportunity cost. Let's say that brings it up to 12 years. Not including maintenance and repairs. It might even need complete replacement at that point. At 50K, which is the real cost, we're talking more like 16-18 years. It seems to me that could change rather dramatically if the price of electricity goes up. I wonder what effect his solar array will have if he buys an electric car that can be plugged in. ### Re:Eh (2, Insightful) #### blue l0g1c (1007517) | about 6 years ago | (#24282615) It's saving them money now. The value of the installation is added to the value of the home. If they ever sold the house, it would justifiably raise the asking price just like a pool, deck, or other improvement to the home. ### Bantha Poodoo (1) #### mckwant (65143) | about 6 years ago | (#24282787) Value of the addon != Increase in house price. The new owner has to want (and be willing and able to pay for) the solar augmentation. It might even be worthless to the new owner, who's not willing to deal with the maintenance. Plus, there's depreciation, replacement cost for the panels and other materials, and so on. If he breaks even on this, either through sale or plain old energy generation, I'll be amazed. ### Re:Eh (1) #### CensorshipDonkey (1108755) | about 6 years ago | (#24282945) Excellent point, and often overlooked. ### Re:Eh (2, Funny) #### Tony Hoyle (11698) | about 6 years ago | (#24282697) No way a panel will last 16-18 years.. Try 2-3. You've got to factor in the price of complete replacecement. Hell, lets say he gets really lucky and they last 10 years.. he's still making a net loss. ### Re:Eh (5, Informative) #### d34thm0nk3y (653414) | about 6 years ago | (#24282769) No way a panel will last 16-18 years.. Try 2-3. You've got to factor in the price of complete replacecement. Hell, lets say he gets really lucky and they last 10 years.. he's still making a net loss. From the Article: These particular panels were guaranteed to deliver 90% of their rated peak capacity for at the twelve year mark, and 80% at the 25 year mark. ### Re:Eh (0) #### Anonymous Coward | about 6 years ago | (#24282719) Mods are smoking crack. You're 100% right. Whatever he's saving in electricity costs, he's spending on a loan to buy panels. And those panels' power diminishes every year. That's also not counting maintenance costs or anything. Also, we're talking about savings in a partial month, during summer where sunlight is at is peak, and where we don't need to heat our homes. I've done the math before, and it would take a good 20 years for to pay for itself. You're essentially just paying someone else i.e. your bank loan instead of the power company. I opted to keep paying the power company, and not having a loan of several 10's of thousands. I'll consider it again once panels come down in price and generate more power. ### Re:Eh (1) #### d34thm0nk3y (653414) | about 6 years ago | (#24282739) From the Article: The payback time, assuming energy costs don't spike steeply, is a little under nine years. If we sell the house, we should get it all back immediately. ### Re:Eh (4, Interesting) #### arth1 (260657) | about 6 years ago | (#24282763) So he saved about$330/month. It cost him $36K (which really cost$50K, but let's say). So it'll take 109 months to get back the money, or 9 years, not adjusting for inflation and investment opportunity cost. Let's say that brings it up to 12 years. Not including maintenance and repairs. It might even need complete replacement at that point. At 50K, which is the real cost, we're talking more like 16-18 years.

It's worse than that. The $11 bill was for 19 days, not a month. And 19 sunny summer days, at that. He won't save$330 per month. Let's see what the figures are after a whole year. My guess is that he'll save around $200, at most. For a$36k investment.

Well a house in Calif* with a clear view of the sky & enough room for 27 solar panels is about $2 million. So it's a choice between saving$250 on electricity or saving $2 million on housing. ### Re:Don't buy a house & save$2 million (1)

#### Jeremi (14640) | about 6 years ago | (#24282717)

Well a house in Calif* with a clear view of the sky & enough room for 27 solar panels is about $2 million. So it's a choice between saving$250 on electricity or saving $2 million on housing California is a big place, and housing prices vary greatly. If you don't mind living out in the sticks, you can buy a house with plenty of land and sky for much less than$2 million.

And of course there are many people who already own a suitable house, or would have bought such a house anyway for other reasons.

### imagine . . . (1)

#### cashman73 (855518) | about 6 years ago | (#24282473)

. . . a beowulf cluster of solar panels on your [mother's] house! It ought to power your beowulf cluster in your [mother's] basement!

### DC - AC - DC (2, Insightful)

#### mcelrath (8027) | about 6 years ago | (#24282477)

So this guy is using DC solar panels, converting it to AC with an inverter, and then using it primarily to power...a computer lab, which just convert it back to DC. There must be at least 50% loss in this. AC was designed for transmission lines, which run for miles.

When the distance from source to sink is measured in meters instead, wouldn't it make sense to avoid the inversion step, and just use a voltage stepdown transformer, keeping everything DC? You'd have to install DC power supplies into your computers. Do those even exist? Of course power not going to computers could be run into an inverter to power other household AC things...

I think the switch to local power generation may require the (re)invention of DC infrastructure for within the house.

-- Bob

### Re:DC - AC - DC (1)

#### david_bonn (259998) | about 6 years ago | (#24282513)

Actually, when solar power is used in a lot of off-the-grid installations a lot of things like lighting are done in DC (dc lights are widely used in RVs so they are pretty commonly available).

Usually an inverter costs you about 30 percent, and I'd agree that converting back to DC would cost about the same.

### Re:DC - AC - DC (0)

#### Anonymous Coward | about 6 years ago | (#24282539)

But he has to convert it to AC to be able to put his power back on the grid.

### Re:DC - AC - DC (4, Informative)

#### MrSteve007 (1000823) | about 6 years ago | (#24282597)

There are indeed losses, but much less than you propose. Most solar DC to AC inverters are 90-93% efficient in their conversions - so only a 7-10% loss. http://www.beaconpower.com/products/SolarInverterSystems/docs/M4_M5_plus_datasheet_web.pdf [beaconpower.com] The same goes for the conversion back to DC on the equipment side.

### Re:DC - AC - DC (1)

#### John.P.Jones (601028) | about 6 years ago | (#24282653)

Very interesting, I think the right thing to do would to run two independent circuits throughout new house construction, standard AC for legacy appliances and DC for a new 'smart' home standard, then add the transformers that inter-convert AC & DC on the centralized power input which takes in both grid power (AC) and solar power (DC) and feeds both circuits (as well as converting DC-solar-out to grid compatible AC), minimizing conversion and centralizing it.

We can even standardize the plugs like this || (AC) vs. |- (DC)

### Re:DC - AC - DC (1)

#### rcw-home (122017) | about 6 years ago | (#24282977)

We can even standardize the plugs like this || (AC) vs. |- (DC)

### Re:DC - AC - DC (1)

#### rcw-home (122017) | about 6 years ago | (#24282687)

So this guy is using DC solar panels, converting it to AC with an inverter, and then using it primarily to power...a computer lab, which just convert it back to DC. There must be at least 50% loss in this.

There are plenty of always-inverting UPSs that are upwards of 90% efficient (pretty much anything over a few kVA capacity). They are AC->DC->AC convertors, so they perform the same steps in a different order.

wouldn't it make sense to avoid the inversion step, and just use a voltage stepdown transformer, keeping everything DC?

Exactly what do you think such a voltage stepdown transformer does?

### Re:DC - AC - DC (1, Redundant)

#### Smitty825 (114634) | about 6 years ago | (#24282695)

Not that I'm an EE or anything (I'm not), but I do know that the higher the voltage on your system, the lower the power lost due to resistance (assuming the same amount of power is transmitted) So even at short distances, it likely makes sense to lose a bit of power for the conversion from DC to high-voltage AC and not lose the power in the line.

(Also, again, I'm not an expert, but I don't believe DC to DC transformers exist. (Flame-proof protective suit on in the likely event I'm wrong) If I'm right, if you wanted to convert 12V DC to 3.3V DC, it would have to be converted to AC before being transformed to a lower voltage...)

### Re:DC - AC - DC (1)

#### Gibbs-Duhem (1058152) | about 6 years ago | (#24282943)

Yes, current through resistance is where power is lost, so higher voltage means less current through your load at the same power.

DC to DC converters do exist, but they're trickier technologically than AC transformers. Instead of relying on basic physical principles of magnetic fields, they use switched outputs, feedback, and filters.

An example of a step down converter is the buck converter. An example of a step up converter is the flyback converter. They generally are based on switching the input voltage on and off over a capacitor + inductor filter so that the average voltage is correct, and the filter smooths the output voltage so it is close to DC.

They are frequently ~90-98% efficient depending on the operating frequency, and can be an order of magnitude smaller than a 60 Hz transformer because they don't need a large inductive core to deal with saturation issues. Not needing an inductive core frequently means they are cost competitive with AC transformers per unit power despite being far more sophisticated (all that raw iron is pricey).

### Re:DC - AC - DC (1)

#### Gibbs-Duhem (1058152) | about 6 years ago | (#24282951)

duh, i obviously meant the line resistance, not the load. obviously the power dissipated in the load is constant.

### Re:DC - AC - DC (1)

#### Max Littlemore (1001285) | about 6 years ago | (#24282979)

, it likely makes sense to lose a bit of power for the conversion from DC to high-voltage AC and not lose the power in the line.

I'm not an EE either, but I have practical experience of living in a house with 12VDC and 240VAC wiring with power generated from small scale hydro. We had a TV that ran on 12VDC or 240VAC which, before we had the inverter to provide 240VAC, used to switch itself off if it was plugged in to the furthest points from the batteries/regulator etc. The voltage drop on the line was enough to cause that, and we had invested in some fairly hefty cables to run the 12V system. Also, the power cupboard, with the batteries, etc, was almost as far from the place in the lounge where we wanted the TV.

I don't remember the efficiency of the inverter, but the fact that we had plenty of water in the creek and therefore plenty of power meant that the conversion was definitely worth it for us.

### Re:DC - AC - DC (0)

#### Christopher_Olah (1317943) | about 6 years ago | (#24282713)

When the distance from source to sink is measured in meters instead, wouldn't it make sense to avoid the inversion step, and just use a voltage stepdown transformer, keeping everything DC? You'd have to install DC power supplies into your computers. Do those even exist? Of course power not going to computers could be run into an inverter to power other household AC things...

No.

DC transformers, in the traditional sense, are impossible for anything longer than a few seconds. A transformer relies not on the existence of an electromagnetic field but on the change of an electromagnetic field.

V=-n \delta \phi / \delta \phi

v_1/v_2 = n_1/n_2

Now, it is possible to step down in some ways. Firstly, you could use a resistor. This means that the rest of your load needs to be known. You could also put you voltage sources in parallel...

Disclaimer: This is just my understanding. I'm a high school student. Don't take my word for it.

### Re:DC - AC - DC (1)

#### btempleton (149110) | about 6 years ago | (#24282883)

As noted, there are losses but not quite so high. Today good PC power supplies are 85% efficient.

You would still need a power supply to use DC. You can get them, they are made for automotive PCs etc. You need to regulate the unreliable power of the panels into the smooth 12v, 5v and other voltages the PCs need. The best way to do this is to invert it to high freq AC and bring it back.

Note that during the non-sunny parts of the day, which last longer than the sunny parts, you would then need to turn grid AC into DC to go into your DC power supply -- and that is even more wasteful.

Ideally you would want a special power supply, able to use DC in the range the panels put out, and also AC, as needed. Not hard to build, but will cost more as it is not made in quantity 1 million.

Note that most solar systems do not run at 12 volts, either, they often run at 36 or 48 or sometimes far more. So you need a PC power supply able to use that unusual voltage.

### Re:DC - AC - DC (1)

#### bavid (842765) | about 6 years ago | (#24282889)

Someone might want to correct me if I'm wrong, but I think that a typical solar inverter will have an efficiency of something around 90% (maybe 80%, to be safe). No idea what the efficiency of a typical PC power supply might be. I think one advantage to going DC-AC-DC is that the AC part is very stiff -- it's connected to the utility and it's not very sensitive to you turning on another machine. Another is that if you want to go DC-DC-AC the DC-AC part needs to be bi-directional, which makes things more complicated and even more expensive. I have heard that telecom stuff tends to be DC, so getting the DC PSUs might be reasonably easy if you knew where to go.

### The Breakdown (1)

so... He states that it was an approximately $36,000 initial investment (http://www.extremetech.com/article2/0,2845,2308684,00.asp). Also, approximately$332 in monthly utility fee savings (http://www.extremetech.com/article2/0,2845,2326045,00.asp). That's just over 9 years before he breaks even, assuming no significant maintenance costs or other "surprises". Not bad... personally I can't wait until this technology improves a bit further and prices drop so the initial investment is a feasible option for the average family!

### Questions? (4, Funny)

#### 140Mandak262Jamuna (970587) | about 6 years ago | (#24282519)

1. How heavy are these solar panels? Easy enough to be lifted and carried down by one or two persons?

2. Are they bolted on? Any locking mechanisms?

3. Is it easy to climb on to the roof?

5. When are you planning to take a vacation?

6. Does it have any kind of GPS thingie or Wifi thingie attached that will phone home?

Thanks buddy.

#### Surt (22457) | about 6 years ago | (#24282683)

1. They are somewhat heavy (50 lbs). They are awkwardly large at 5ftx3ft. Two person job if you don't want to risk a rooftop fall.

2. They are typically bolted on. Uninstall time will be in the several minutes per panel range. Be sure you have an electrician with you to avoid death by electric shock.

3. You can see in the pictures he has a typical roof. Bring a ladder. And a crane if you want an easier time lowering the panels.

4. Yes, see the pictures.

5. Don't know about that one. Probably end of December or next summer.

6. Doubtful.

### Hail (2, Insightful)

#### shaitand (626655) | about 6 years ago | (#24282589)

I hate articles like this because they mislead people. Solar is NOT a way to save money and every sucker who is drawn in by this idea will be turned off solar for a long time.

These kind of articles always ignore the real costs and usually just look at the cost of the panels. But the panels aren't the only consideration, you have to consider the cost of the battery bank and the cost of replacing the batteries periodically. You won't get the full life out the batteries either, that constant charge and discharge is going to reduce the capacity of those batteries quickly.

The other cost is both in terms of economics and comfort. To actually be able to come close to living on that small solar output you are going to need to install all new appliances and run a water heater that will deliver luke warm water at best. You are going to have to come to terms with being frugile with power in almost action you take from there on in.

### Re:Solar is not a good choice if you want to save (5, Informative)

#### cassius2002 (675501) | about 6 years ago | (#24282655)

Residential solar installations typically have no batteries, so there is no maintenance cost for batteries, nor replacement costs. This type of installation uses the grid as a kind of giant battery, feeding power to the grid during the day and drawing from the grid at night.

### Re:Solar is not a good choice if you want to save (1)

#### Darkk (1296127) | about 6 years ago | (#24282863)

I like this approach better and it's a win / win for everybody.

### Re:Solar is not a good choice if you want to save (1)

$11.34 + this months payment on the loan covering the costs of installation + costs of maintenance and operation. ### pink (3, Funny) #### Anonymous Coward | about 6 years ago | (#24282699) He's should've bought like 2 less solar panels and used the money to paint his house some color other than pink. ### Do the math -- is he really saving money? (3, Insightful) #### btempleton (149110) | about 6 years ago | (#24282851) Today it's hard to make solar actually pay for itself. At California's high-tier rates, it is possible, but still takes a lot of work. He says he put in$36,000 and will save $3,300 per year in payments to the power company. Now the historical annual rate of return of an S&P 500 index fund is 11.3% over the last century, so$36K put there would return over $4,000 -- enough to pay the$3,300 to the grid, have $700 left over and of course, still keeping the principal. Compared to that, the panels are losing money each year and will never pay for themselves -- unless grid power goes up a lot. And grid power might go up, but only so far. Because eventually the grid power hits the solar price, and the grid itself starts putting in solar sources at that price -- because it's cheaper. Most solar installations lose money hand over fist outside of California's high priced tiers. Today, solar comes in about 20 cents/kwh (at more like a 6% interest rate, not the 11.3% rate of the stock market.) Try this spreadsheet: To work out the real cost. It's worse if you consider that at the true cost of the system before rebates --$48K if I read right, it really loses money.

Now, I'm not saying it's not good to put in solar to be greener, or that the government shouldn't be providing subsidies to make this happen.

I just don't want people to use the wrong math to think they are saving money, when in fact they are spending more (for a purpose.)

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