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Switching To Solar Power — Six Months Later
ThinSkin writes "Slashdot readers may remember an article regarding ExtremeTech's Loyd Case's experiences with solar power for the home after one month of usage. During that time six months ago, it sure seemed like a great deal, but the tables have turned significantly once winter approached. While it's no surprise solar power generation is expected to dwindle during the winter, Loyd compares solar power data of the last six months to determine if solar power is still worth the time and money."
Who the hell uses that much electric power?
I want to delete my account but Slashdot doesn't allow it.
There's an important step that this guy missed: cutting consumption. I have a roughly 3000 square foot house, and the most I've used since August '07 is 700kWh in a month... and that was a month when I had visitors for basically the whole month, so we used a lot more power. My average is around 500.
Now... we don't know how big this guy's house is, or how many people live there. But really... 1,635kWh? That seems pretty excessive for any reasonable house. Maybe if he's got a bunch of servers on all the time, and has electric heat, and lives in a cold climate, but it still seems high.
Why didn't this follow up article include a Return on Investment number? It would be nice if he would have included the cost of the install and compare it to the difference in his electric bills. I'm curious to see how long it will take the install to pay for itself.
Who ever installed the panels mounted them directly flat on the roof. That is bad.
They need to be angled for the best sun during the time the power need is greatest. Ideally they would be adjustable semi-annually/quarterly/monthly for the best angle. And if fixed would be biased toward the point of worst number of sun days and power need.
Doing a suboptimal installation and not accounting for sun angle is not a good installation and should be perform at a fraction of potential output.
Yes the panels will drop in cost, but you are forgetting that Electric bills are going to go UP in price over the same time. 10 years from now, he can generate the same amount of power, and save more money than he does today.
Of course, those that wait will have a MUCH quicker payback, since their equipment goes down in cost, and rates go up. But then again, you probably don't own a computer, do you? Cause there is always one that is faster/cheaper coming in another few months. Sometimes you just gotta jump in.
What are we going to do tonight Brain?
I went back to his original article (the instalation). He said the estimate is that his anual utility bill will drop from 4400 a year to 1100 a year.
So I made a few assumptions.
#1-his power use will not increase. Not really likely but a future increase shouldn't change the ROI on his current investment.
#2-Utilities will just keep pace with inflation (assumed 2%)...power costs will stay porportinally expensive in the future. This is probably not ture as power prices tend to increase slightly faster than inflation. So this assumption will tend to increase the ROI.
#3-I assume he is financing it through his mortgage at about 5%
Therefore when I calculate out to 25 years I find that he would spend about $141,000 in power over the 25 years without slar. With Solar he would spend $35,233.
The Payoff date comes at about 12.5 years.
Because this is a follow up article. The first article includes the Roi figures along with the fact that California Rebated half the cost of the system ($36,000.00 dollars), which explains his up front costs of $36,000.00. Not bad for the size system he had installed and yes I've read the first article and understood the reasoning for the selected installation method, which was to reduce peak Energy Usage during Peak Summer Cost. That's right, his goal was to cut the summer cost of energy during the most expensive part of the year from PG&E (his uutility company).
Note that PG&E has a variable Rate cycle that has the greatest impact during the summer cooling period. This is why he wanted to reduce his summer electric costs, which the system did quite successfully.
Mod me up/Mod me down: I wont frown as I've no crown
MAKE:blog has some descriptions of some DIY sun-trackers to move the panel with the sun during the day.
Don't tell anyone, but there's a tab on the first page that's labeled "print". I don't get to wait for ads and pictures to load, but it has the text.
The cost of that cleanup, of course, will be borne by taxpayers, not industry.
I thought that only happened in Soviet Russia.
Slow down, cowboy! It has been 4 hours since you last posted. You must wait another few hours.
That article has a lot of consumption and billing numbers for each of utility and homegrown power, but it's hard to get exact performance comparisons because the numbers don't exactly measure the same things. There is no exact start and end date, just month names, and approximate mentions of offsets into them, not lining up generation and billing dates in either the solar generation half-year or the time before drawing from only the utility. And practically no data on income from overgenerating, selling back to utility or grid.
But there is enough data to make rough comparisons. They say their January/utility bill was $446, but their December bills are the highest (all of which extra usage was billed in the highest rate, 300% of the base rate). So let's say their average bill used to be $450:mo, or $5600 annually. However, they said up front that their annual bill is about $4400. We'll take the average of $5400. Now their July-December/solar bill is $389.39. Even if we call that $400, and so their annual/solar bill is $800, they're saving $4600 a year. They paid about $55,000 before rebates, about $37,000 after all rebates. Their utility bill savings pays off their installation investment in $37,000 / $4600 = 8.04 years. Pessimistically, they should be paid off in 9 years.
These systems have a minimum lifetime of 30 years (if you don't invest in an upgrade during that time). Even if energy rates stay the same in those 30 years (probably not, probably higher), that $4600 for 21 more years is $96,600, or 2.6x the installation cost. Total return is $133,600 on $37,000 investment, so 3600% Return on Investment over 30 years. If you invested that money in a compound interest account (either savings or some investment with an average annual return reinvested), you'd have to get 15.43% annual compound interest to turn $37K into $136K in 30 years. Conversely, if you took out a 30 year mortgage on your home at today's average rate of 5.63%, you'd net 9.8% benefit. Which means that it's worth mortgaging (part of) your home to invest in these, with a fraction of your old utility bills paid as mortgage interest, and getting $78K more ("profit", really utilities savings) after 30 years, with no out of pocket.
That could be even better than they say. Their reasons for failing to maximize their roof generating area don't seem compelling: "it would get a little crowded up there". Other than access to the panels for cleaning, who cares how crowded it is? It looks like they could double their area. Which would give them closer to zero Winter bills, but overkill in Summer that exceeds what's left (if any) during Winter, which exceeds their "zero annual bill" maximum for reselling overgeneration to the utility at retail rates. So probably about 1.5x the area would give them Summer overgeneration that would equal their Winter utility draw, netting zero bills. It's got to cost less than 1.5x to install just more area, because labor and shared components (especially the inverter that sells power back to the utility) are a substantial cost that doesn't increase at all at that rate. Say it costs 1.2x, or $44,400, but they save the full $5400 annually. That's still about the same time in payback (about 2% longer), but 3.7x the return. And the "green feeling" is complete.
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make install -not war
Al Gore's carbon footprint should be measured against people with similar incomes, not against the average Joe.
No, it shouldn't. If Al Gore insists on promoting things like the Kyoto Accord that measure country's carbon footprints independently of income, then he should expect the same on an individual basis. Anything less is total hypocrisy.