Here comes the Sun.
July 23, 2015 12:31 PM Subscribe
What I want to know is whether there is an advantage to putting up a couple of panels or do you need to go whole hog?
posted by dances_with_sneetches at 1:04 PM on July 23, 2015
posted by dances_with_sneetches at 1:04 PM on July 23, 2015
Dances_with_sneetches: A significant part of the cost is for the installation and the inverters so the best option is to go "whole hog" IMO.
I had a rooftop system of 7kw installed 2 years ago and am very pleased with it. It was the maximum I could put on my south facing roof section. I am over generating by about 40% so I get a pretty good chunk of money back from the utility company.
It should be noted that the first thing to do, and get the best return on investment from, is energy conservation, then look at generation.
posted by nofundy at 1:17 PM on July 23, 2015 [2 favorites]
I had a rooftop system of 7kw installed 2 years ago and am very pleased with it. It was the maximum I could put on my south facing roof section. I am over generating by about 40% so I get a pretty good chunk of money back from the utility company.
It should be noted that the first thing to do, and get the best return on investment from, is energy conservation, then look at generation.
posted by nofundy at 1:17 PM on July 23, 2015 [2 favorites]
I did some contract work for a solar company in 2008-2009 and it's been pretty amazing to see the prices continue to collapse even since then. Back then, $5 per peak watt, installed, was like the greatest deal for a huge installation; now it's par for the course (or even on the high end!) for a home array. Wow.
What I want to know is whether there is an advantage to putting up a couple of panels or do you need to go whole hog?
Well, you'd get some benefit, but the issue is that you can't really save much on "balance of system" components just by limiting yourself to a small array. If you are going to connect your system to the grid (and if you want to go off-grid, that's a whole other HUGE expense), you still need the inverters and transformers to interact with main-line power in a safe, code-compliant manner, and those only get so cheap.
If you're cost constrained, though, at this point in history the better option is probably to go for a zero down lease arrangement. (This is basically Solar City's entire business model, for instance.) Essentially, the solar company installs stuff on your roof, maintains ownership of it, and sells you the power at a fixed rate for 10, 15, 20 years, etc.
posted by Joey Buttafoucault at 1:24 PM on July 23, 2015
What I want to know is whether there is an advantage to putting up a couple of panels or do you need to go whole hog?
Well, you'd get some benefit, but the issue is that you can't really save much on "balance of system" components just by limiting yourself to a small array. If you are going to connect your system to the grid (and if you want to go off-grid, that's a whole other HUGE expense), you still need the inverters and transformers to interact with main-line power in a safe, code-compliant manner, and those only get so cheap.
If you're cost constrained, though, at this point in history the better option is probably to go for a zero down lease arrangement. (This is basically Solar City's entire business model, for instance.) Essentially, the solar company installs stuff on your roof, maintains ownership of it, and sells you the power at a fixed rate for 10, 15, 20 years, etc.
posted by Joey Buttafoucault at 1:24 PM on July 23, 2015
Is using solar hot water to supplement natural gas cheaper or more cost effective than photovoltaic power? Solar hot water tech is less exciting and therefore seems to get less press. But, when your power is primarily hydroelectric, it makes more sense to look for non-electric ways to reduce carbon emissions.
posted by spreadsheetzu at 2:03 PM on July 23, 2015 [1 favorite]
posted by spreadsheetzu at 2:03 PM on July 23, 2015 [1 favorite]
Regarding graph 12, IINM, we're paying closer to 20ยข/kwh in Connecticut.
posted by ZenMasterThis at 2:18 PM on July 23, 2015
posted by ZenMasterThis at 2:18 PM on July 23, 2015
by the way the california utilities are poised to kill rooftop solar in the next couple of years. the original rules for net metering say that when the sum of all rooftop generation is 5% of the total generated electricity (in each region - PGE, Edison, San Diego), that the net metering program can be ended. supposedly in san diego, they are almost already there. if 5% is never met, they can still end the programs on july 1, 2017.
anyone who installs before then will be grandfathered in, but if they really get the CPUC to end net metering, the economics of home PV are going to get turned upside-down. past the end of net metering, the utilities want to sell you electricity at retail and then buy electricity from you at wholesale, which basically makes those single and small-double digit monthly bills a thing of the past. at that point no one in their right mind will install a home PV system.
a similar story happened in hawaii, where the electric company started pushing back real hard, to the point that they would not certify systems for interconnection to the grid for months. people had their builds finished and sitting idle for months.
the federal tax credit also expires at the end of 2016, and if that's not renewed, that's going to put a dent in things as well.
if california is trying to kill rooftop solar, i don't hold out a lot of hope for the rest of the country.
posted by joeblough at 2:45 PM on July 23, 2015 [3 favorites]
anyone who installs before then will be grandfathered in, but if they really get the CPUC to end net metering, the economics of home PV are going to get turned upside-down. past the end of net metering, the utilities want to sell you electricity at retail and then buy electricity from you at wholesale, which basically makes those single and small-double digit monthly bills a thing of the past. at that point no one in their right mind will install a home PV system.
a similar story happened in hawaii, where the electric company started pushing back real hard, to the point that they would not certify systems for interconnection to the grid for months. people had their builds finished and sitting idle for months.
the federal tax credit also expires at the end of 2016, and if that's not renewed, that's going to put a dent in things as well.
if california is trying to kill rooftop solar, i don't hold out a lot of hope for the rest of the country.
posted by joeblough at 2:45 PM on July 23, 2015 [3 favorites]
Is using solar hot water to supplement natural gas cheaper or more cost effective than photovoltaic power?
No, solar hot water doesn't make sense at small scale anymore. For an apartment building, hotel, laundromat, sure, but for a house, the cost is high, the complexity is high, and the maintenance cost is high. Solar PV plus an electric hot water tank is cheaper, lower maintenance, and much more efficient (because you not will waste a lot of energy when your water is already hot and there is no demand, especially in the summer).
Solar hot water doesn't get much press anymore because it just doesn't make sense.
Depending on our climate and house particulars, a heat pump water tank may make a lot of sense. If you can get off gas entirely, that's definitely for the best (and, here in BC, the monthly charge of $12 might entirely erase the price advantage of gas over electricity if you aren't doing anything other than heating hot water with gas).
posted by ssg at 3:00 PM on July 23, 2015 [1 favorite]
No, solar hot water doesn't make sense at small scale anymore. For an apartment building, hotel, laundromat, sure, but for a house, the cost is high, the complexity is high, and the maintenance cost is high. Solar PV plus an electric hot water tank is cheaper, lower maintenance, and much more efficient (because you not will waste a lot of energy when your water is already hot and there is no demand, especially in the summer).
Solar hot water doesn't get much press anymore because it just doesn't make sense.
Depending on our climate and house particulars, a heat pump water tank may make a lot of sense. If you can get off gas entirely, that's definitely for the best (and, here in BC, the monthly charge of $12 might entirely erase the price advantage of gas over electricity if you aren't doing anything other than heating hot water with gas).
posted by ssg at 3:00 PM on July 23, 2015 [1 favorite]
Our solar hot water was a lot less expensive than our panels, and maintenance has been non-existent, other than a yearly check out/ tune up. Depends on how many people in your house and how many baths you like to take.
posted by Windopaene at 3:16 PM on July 23, 2015 [1 favorite]
posted by Windopaene at 3:16 PM on July 23, 2015 [1 favorite]
Best home-solar roundup I've ever seen.
Which is amazing, because there's all that untapped potential. Seen much online advertising for home solar? I haven't.
Observations:
* how much the cost has dropped (not even counting constant dollars)
* he doesn't even seem to be using any storage. "We actually use under 25% because nothing is on during the weekday periods."
He could add a ~ $3K Tesla battery to that setup and get significantly better payback time.
* this is almost unique in providing comparison facts for the whole world.
Maybe world leaders will wake up to how much rising seas will cost ... in dollars and in lives. Maybe not.
BTW, another thought: Inverters waste power. For some people, buying appliances that make direct use of solar may make sense.
posted by Twang at 4:40 PM on July 23, 2015 [1 favorite]
Which is amazing, because there's all that untapped potential. Seen much online advertising for home solar? I haven't.
Observations:
* how much the cost has dropped (not even counting constant dollars)
* he doesn't even seem to be using any storage. "We actually use under 25% because nothing is on during the weekday periods."
He could add a ~ $3K Tesla battery to that setup and get significantly better payback time.
* this is almost unique in providing comparison facts for the whole world.
Maybe world leaders will wake up to how much rising seas will cost ... in dollars and in lives. Maybe not.
BTW, another thought: Inverters waste power. For some people, buying appliances that make direct use of solar may make sense.
posted by Twang at 4:40 PM on July 23, 2015 [1 favorite]
No, solar hot water doesn't make sense at small scale anymore.
Anymore - why, what changed? Are you speaking for the entire world, or just your backyard?
the cost is high, the complexity is high, and the maintenance cost is high.
In my experience, none of those things are true, especially complexity [WTF?]
Solar PV plus an electric hot water tank is cheaper, lower maintenance, and much more efficient. (because you not will waste a lot of energy when your water is already hot and there is no demand, especially in the summer)
Piffle - you're trying to tell us that solar PV -> heat is efficient? Solar to heat is much more efficient than PV, and in this part of the world we take showers year-round.
posted by HiroProtagonist at 9:52 PM on July 23, 2015 [3 favorites]
Anymore - why, what changed? Are you speaking for the entire world, or just your backyard?
the cost is high, the complexity is high, and the maintenance cost is high.
In my experience, none of those things are true, especially complexity [WTF?]
Solar PV plus an electric hot water tank is cheaper, lower maintenance, and much more efficient. (because you not will waste a lot of energy when your water is already hot and there is no demand, especially in the summer)
Piffle - you're trying to tell us that solar PV -> heat is efficient? Solar to heat is much more efficient than PV, and in this part of the world we take showers year-round.
posted by HiroProtagonist at 9:52 PM on July 23, 2015 [3 favorites]
I think that solar water heating is much more popular outside of the US, particularly in Israel:
...in 1980 the Israeli Knesset passed a law requiring the installation of solar water heaters in all new homes (except high towers with insufficient roof area). As a result, Israel is now the world leader in the use of solar energy per capita with 85% of the households today using solar thermal systems (3% of the primary national energy consumption), estimated to save the country 2 million barrels (320,000 m3) of oil a year, the highest per capita use of solar energy in the world.
posted by 445supermag at 10:12 PM on July 23, 2015
...in 1980 the Israeli Knesset passed a law requiring the installation of solar water heaters in all new homes (except high towers with insufficient roof area). As a result, Israel is now the world leader in the use of solar energy per capita with 85% of the households today using solar thermal systems (3% of the primary national energy consumption), estimated to save the country 2 million barrels (320,000 m3) of oil a year, the highest per capita use of solar energy in the world.
posted by 445supermag at 10:12 PM on July 23, 2015
Piffle - you're trying to tell us that solar PV -> heat is efficient? Solar to heat is much more efficient than PV, and in this part of the world we take showers year-round.
Not saying I agree since I know very little about solar, but I understood the point to be that in summer a solar thermal system will quickly heat the water tank up to HOT and then the rest of the insolation isn't usefully harvested. Whereas a PV system just keeps pumping out electricity whether you need it or not.
posted by ROU_Xenophobe at 10:57 PM on July 23, 2015
Not saying I agree since I know very little about solar, but I understood the point to be that in summer a solar thermal system will quickly heat the water tank up to HOT and then the rest of the insolation isn't usefully harvested. Whereas a PV system just keeps pumping out electricity whether you need it or not.
posted by ROU_Xenophobe at 10:57 PM on July 23, 2015
but if they really get the CPUC to end net metering, the economics of home PV are going to get turned upside-down. past the end of net metering, the utilities want to sell you electricity at retail and then buy electricity from you at wholesale, which basically makes those single and small-double digit monthly bills a thing of the past.
But net metering is unsustainable. The power companies pay far less than retail prices when they buy power from giant power plants, yet they are expected to pay top dollar for a couple kWh from Joe's rooftop? That's like me walking into my local Safeway and demanding that they buy my homemade jam at twice what they pay Smucker's and sell it for the same price regardless of demand or the underlying economics of the jams and jellies market. With home PV, you are a retail customer and very small supplier, so it's not remotely surprising that the utilities want to charge and pay you accordingly.
Ultimately, what we're facing in California is a pattern of power usage known as the Duck Chart. (Note that others call this a load of nonsense peddled by the investor-owned utilities to kill rooftop solar; both, to a certain extent, are probably right.) The basic idea is that net power needs (after solar is accounted for) will spike ~13,000 MW statewide in a couple hours in the evening as solar generation drops to zero just as residential power use ramps up. On the other side, net load drops to comparatively low levels during the day, which is wonderful, but power plants don't just turn on and off on command. You mentioned Hawaii, where this is very much a problem today.
There are definitely things we can do that will help. Energy storage technology, whether it's Tesla's Powerwall or larger scale systems that can be operated by utilities, can help, though we're still figuring out the financial models that can make them work at scale. Solar proponents are big on demand-side solutions to encourage people to use less energy during the period when demand spikes, though it's easy to be skeptical.
We're quickly reaching the point in California where home solar will have a substantial impact on the market for electricity (California's energy market being a decidedly ugly place, as those of us who recall not having any power in 2000-2001 will tell you). Dealing with that is complex, expensive, and involves a bunch of powerful players fighting to make sure they aren't left holding the bag. It's not going to be pretty.
posted by zachlipton at 12:35 AM on July 24, 2015
But net metering is unsustainable. The power companies pay far less than retail prices when they buy power from giant power plants, yet they are expected to pay top dollar for a couple kWh from Joe's rooftop? That's like me walking into my local Safeway and demanding that they buy my homemade jam at twice what they pay Smucker's and sell it for the same price regardless of demand or the underlying economics of the jams and jellies market. With home PV, you are a retail customer and very small supplier, so it's not remotely surprising that the utilities want to charge and pay you accordingly.
Ultimately, what we're facing in California is a pattern of power usage known as the Duck Chart. (Note that others call this a load of nonsense peddled by the investor-owned utilities to kill rooftop solar; both, to a certain extent, are probably right.) The basic idea is that net power needs (after solar is accounted for) will spike ~13,000 MW statewide in a couple hours in the evening as solar generation drops to zero just as residential power use ramps up. On the other side, net load drops to comparatively low levels during the day, which is wonderful, but power plants don't just turn on and off on command. You mentioned Hawaii, where this is very much a problem today.
There are definitely things we can do that will help. Energy storage technology, whether it's Tesla's Powerwall or larger scale systems that can be operated by utilities, can help, though we're still figuring out the financial models that can make them work at scale. Solar proponents are big on demand-side solutions to encourage people to use less energy during the period when demand spikes, though it's easy to be skeptical.
We're quickly reaching the point in California where home solar will have a substantial impact on the market for electricity (California's energy market being a decidedly ugly place, as those of us who recall not having any power in 2000-2001 will tell you). Dealing with that is complex, expensive, and involves a bunch of powerful players fighting to make sure they aren't left holding the bag. It's not going to be pretty.
posted by zachlipton at 12:35 AM on July 24, 2015
No, solar hot water doesn't make sense at small scale anymore. For an apartment building, hotel, laundromat, sure, but for a house, the cost is high, the complexity is high, and the maintenance cost is high. Solar PV plus an electric hot water tank is cheaper, lower maintenance, and much more efficient (because you not will waste a lot of energy when your water is already hot and there is no demand, especially in the summer).
I beg to differ, the systems are stupid simple unless you live someplace where it get below freezing a lot, and even then a closed loop glycol system can deal with that.
I have the same system that was installed on my roof in 1990 and the only real maintenance was changing the dielectric connectors on the storage tank.
The whole thing could be run by a aurduino if I cared to replace the 25 year old temp unit.
It cost $2400 in 1990.
posted by boilermonster at 12:38 AM on July 24, 2015
I beg to differ, the systems are stupid simple unless you live someplace where it get below freezing a lot, and even then a closed loop glycol system can deal with that.
I have the same system that was installed on my roof in 1990 and the only real maintenance was changing the dielectric connectors on the storage tank.
The whole thing could be run by a aurduino if I cared to replace the 25 year old temp unit.
It cost $2400 in 1990.
posted by boilermonster at 12:38 AM on July 24, 2015
Anymore - why, what changed? Are you speaking for the entire world, or just your backyard?
Solar PV got cheaper is what changed. This is for Canada and the US in general (which is the focus of the FPP). There may be exceptions and the situation certainly may be different where you are.
In my experience, none of those things are true, especially complexity [WTF?]
Solar thermal is definitely more complex than PV. Your PV panels come with a 25+ year power generation guarantee. Solar thermal does not. All of this is even worse if you live in a place where it freezes (like much of the US and Canada), so you need glycol and a heat exchanger.
As far as efficiency, ROU_Xenophone has it exactly. The problem is that you want to size the system to provide most of your hot water, but then you end up with excess capacity when there is more sun than average and have to rely on a backup energy source when there is less (and you have the problem of seasonal variability as well with less sun and colder incoming water in the winter).
If you have PV instead with net metering, you use or sell all the energy you generate. It just makes more sense to add more solar panels instead and use the electricity generated to heat water, especially if a heat pump hot water heater makes sense for you. You can buy a lot of solar PV for the cost of a thermal system.
Maybe with a large family and high hot water use somewhere that it never freezes, solar thermal still makes sense. However, in climates where air conditioning is used for a good part of the year, a heat pump hot water tank is very cheap to operate (because it supplies cooling). When paired with water conservation measures (efficient appliances, low flow showers, good habits), I'd bet that solar PV will still be cheaper in the long run.
posted by ssg at 1:01 AM on July 24, 2015
Solar PV got cheaper is what changed. This is for Canada and the US in general (which is the focus of the FPP). There may be exceptions and the situation certainly may be different where you are.
In my experience, none of those things are true, especially complexity [WTF?]
Solar thermal is definitely more complex than PV. Your PV panels come with a 25+ year power generation guarantee. Solar thermal does not. All of this is even worse if you live in a place where it freezes (like much of the US and Canada), so you need glycol and a heat exchanger.
As far as efficiency, ROU_Xenophone has it exactly. The problem is that you want to size the system to provide most of your hot water, but then you end up with excess capacity when there is more sun than average and have to rely on a backup energy source when there is less (and you have the problem of seasonal variability as well with less sun and colder incoming water in the winter).
If you have PV instead with net metering, you use or sell all the energy you generate. It just makes more sense to add more solar panels instead and use the electricity generated to heat water, especially if a heat pump hot water heater makes sense for you. You can buy a lot of solar PV for the cost of a thermal system.
Maybe with a large family and high hot water use somewhere that it never freezes, solar thermal still makes sense. However, in climates where air conditioning is used for a good part of the year, a heat pump hot water tank is very cheap to operate (because it supplies cooling). When paired with water conservation measures (efficient appliances, low flow showers, good habits), I'd bet that solar PV will still be cheaper in the long run.
posted by ssg at 1:01 AM on July 24, 2015
But net metering is unsustainable. The power companies pay far less than retail prices when they buy power from giant power plants, yet they are expected to pay top dollar for a couple kWh from Joe's rooftop?
cry me a river, IOUs. you're not paying top dollar for my electricity. i'm simply not buying it from you, and instead am providing it for myself. for most of NEM-1 they have not ever been paying anyone for rooftop solar - your bills just zeroed out if you had excess generation. very recently they have been forced to pay wholesale for the balance by the CPUC.
i understand that an electric utility must balance supply and demand at all times due to basic physics but their concerns are not technical, they are financial. bottom line is that "Investor Owned Utility" is a bullshit concept - PGE, SDGE and SCE's constituents are their shareholders, not their customers. they are doing all they can to kill distributed renewables because it's not a path to financial growth for them.
posted by joeblough at 9:03 AM on July 24, 2015
cry me a river, IOUs. you're not paying top dollar for my electricity. i'm simply not buying it from you, and instead am providing it for myself. for most of NEM-1 they have not ever been paying anyone for rooftop solar - your bills just zeroed out if you had excess generation. very recently they have been forced to pay wholesale for the balance by the CPUC.
i understand that an electric utility must balance supply and demand at all times due to basic physics but their concerns are not technical, they are financial. bottom line is that "Investor Owned Utility" is a bullshit concept - PGE, SDGE and SCE's constituents are their shareholders, not their customers. they are doing all they can to kill distributed renewables because it's not a path to financial growth for them.
posted by joeblough at 9:03 AM on July 24, 2015
Solar thermal is definitely more complex than PV. Your PV panels come with a 25+ year power generation guarantee. Solar thermal does not. All of this is even worse if you live in a place where it freezes (like much of the US and Canada), so you need glycol and a heat exchanger.
You're thinking old tech if you need glycol and a heat exchanger. Modern evacuated tube solar thermal doesn't need this.
And as for maintenance - in my experience it's been install & forget.
As far as efficiency, ROU_Xenophone has it exactly. The problem is that you want to size the system to provide most of your hot water, but then you end up with excess capacity when there is more sun than average and have to rely on a backup energy source when there is less (and you have the problem of seasonal variability as well with less sun and colder incoming water in the winter).
If you have PV instead with net metering, you use or sell all the energy you generate
Net metering generally only makes sense with heavy subsidies - I'd never consider it, and I'm unlikely to lose sleep over the fact that I didn't utilise 100% of my sunshine. If that was the case, the efficiency of PV itself would have you tossing & turning.
For my setup using a combined Thermal Solar + logburner to heat water makes a lot more economic [and space] sense than trying to install enough PV to heat water.
posted by HiroProtagonist at 8:56 PM on July 26, 2015
You're thinking old tech if you need glycol and a heat exchanger. Modern evacuated tube solar thermal doesn't need this.
And as for maintenance - in my experience it's been install & forget.
As far as efficiency, ROU_Xenophone has it exactly. The problem is that you want to size the system to provide most of your hot water, but then you end up with excess capacity when there is more sun than average and have to rely on a backup energy source when there is less (and you have the problem of seasonal variability as well with less sun and colder incoming water in the winter).
If you have PV instead with net metering, you use or sell all the energy you generate
Net metering generally only makes sense with heavy subsidies - I'd never consider it, and I'm unlikely to lose sleep over the fact that I didn't utilise 100% of my sunshine. If that was the case, the efficiency of PV itself would have you tossing & turning.
For my setup using a combined Thermal Solar + logburner to heat water makes a lot more economic [and space] sense than trying to install enough PV to heat water.
posted by HiroProtagonist at 8:56 PM on July 26, 2015
You obviously have a very different situation in NZ.
You're thinking old tech if you need glycol and a heat exchanger. Modern evacuated tube solar thermal doesn't need this.
Evacuated tubes still need glycol anywhere with serious cold in the winter. Almost everywhere in Canada and much of the US need glycol in evacuated tubes - and that means more maintenance and more cost.
Net metering generally only makes sense with heavy subsidies
This is not true anymore in Canada or the US.
trying to install enough PV to heat water.
You make it sound like some difficult task in that you somehow "try" to install enough PV to heat water. With a heat pump tank, that's about 5 panels depending on your water use and insolation. That's not very much.
posted by ssg at 5:04 PM on July 27, 2015
You're thinking old tech if you need glycol and a heat exchanger. Modern evacuated tube solar thermal doesn't need this.
Evacuated tubes still need glycol anywhere with serious cold in the winter. Almost everywhere in Canada and much of the US need glycol in evacuated tubes - and that means more maintenance and more cost.
Net metering generally only makes sense with heavy subsidies
This is not true anymore in Canada or the US.
trying to install enough PV to heat water.
You make it sound like some difficult task in that you somehow "try" to install enough PV to heat water. With a heat pump tank, that's about 5 panels depending on your water use and insolation. That's not very much.
posted by ssg at 5:04 PM on July 27, 2015
With a heat pump tank, that's about 5 panels depending on your water use and insolation.
Your original point was for solar thermal "the complexity is high, and the maintenance cost is high", when compared to PV. I don't think this is a valid point if the PV solution relies on a heat pump.
posted by HiroProtagonist at 8:07 PM on July 27, 2015
Your original point was for solar thermal "the complexity is high, and the maintenance cost is high", when compared to PV. I don't think this is a valid point if the PV solution relies on a heat pump.
posted by HiroProtagonist at 8:07 PM on July 27, 2015
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