Does Solar Pay for Itself? Is it worth it?
- Thread starter BentleyJ
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wattmatters
Solar Wizard
How did you arrive at that?
1 kWh = 3,600,000 J
$0.50/kWh = $0.00000014/J
Do you mean MJ?
1 kWh = 3.6 MJ
$0.50/kWh = $0.1389/MJ
With a heat pump COP of 3.0, that's 4.6 cents/MJ.
Hedges
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Thanks, corrected my units to GJ
wattmatters
Solar Wizard
Here's the thing with heat pumps.
It would be more effective use of the gas to generate electricity with it at a power plant and deliver electricity to your home (including all the transmission losses) to be heated with a heat pump than to burn the gas directly at home in a furnace.
It may or may not cost less but it would sure help reduce emissions. Especially as the energy sources for heat pumps can also be from renewable energy.
Hedges
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More effective use of gas to generate electricity somewhere waste heat can be utilized. Sometimes that can be near a central plant (but likely not a utility scale plant.)
But the key is, ICE CHP at the home might be 30% efficient generating electricity, while combined cycle generator at power plant might be 60% (has steam turbine down stream of gas turbine.)
Fuel cell CHP at home could be the most efficient. They do exist, but I'm not so sure about cost effectiveness. Likely retail/wholesale spread makes them competitive.
But the key is, ICE CHP at the home might be 30% efficient generating electricity, while combined cycle generator at power plant might be 60% (has steam turbine down stream of gas turbine.)
Fuel cell CHP at home could be the most efficient. They do exist, but I'm not so sure about cost effectiveness. Likely retail/wholesale spread makes them competitive.
matttelz
New Member
I just did some back of the napkin calculations for the cost of a small solar system and payback period. Doing all of it myself as a grid tie system I’m seeing a 6 year break even time at current electric prices + the 30% EPA tax credit…
Not sure if increasing or decreasing the kw size would shorten the break even time… I use like 600kw/month so i would need a massive system to totally offset my electric usage…
Not sure if increasing or decreasing the kw size would shorten the break even time… I use like 600kw/month so i would need a massive system to totally offset my electric usage…
LeoThomson
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My current thinking is that using serious energy reducing measures, combined with extra large rooftop solar + batteries is the way to go.
However I can't imagine that exporting electricity in summer and getting it back in winter is sustainable from the perspective of the large generators who can't make money from their investment in summer.
Hedges
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I think rooftop PV was a good fit when large generators couldn't handle the A/C loads, and winter heating for most was from natural gas.
Things may change in the future.
I believe if we rooftop PV producers called a Solar Embargo and shut off our systems some hot summer's day, the grid would collapse. Utility and wholesale have not invested enough to sell the power people want to buy. Now PG&E want to make excessive markup on the backs of we who paid higher retail prices for generation capacity. As a producing bloc, we could "negotiate" what our power is worth.
Things may change in the future.
I believe if we rooftop PV producers called a Solar Embargo and shut off our systems some hot summer's day, the grid would collapse. Utility and wholesale have not invested enough to sell the power people want to buy. Now PG&E want to make excessive markup on the backs of we who paid higher retail prices for generation capacity. As a producing bloc, we could "negotiate" what our power is worth.
timselectric
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Yes, switching out my 3 ton unit to a heat pump. With gas as my second stage. Will do the same thing for domestic water heating.
wattmatters
Solar Wizard
Well I'm not sure why anyone would.
In Australia we have states that, at times, have 100% of their entire grid demand powered by rooftop solar PV alone. It's becoming a regular occurrence on those lovely mild sunny Spring days.
Hedges
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Our utilities and PUC negotiate with wholesale producers, but shove pricing down the throats of rooftop PV generators.
They pretend the value of our power is the price of the last kWh produced (which on rare occasion they've paid another state to take off their hands.)
If we unplugged and collapsed the grid, we would then be in a place to negotiate what price they must credit us to access the power we have available. They can consider what fuel, generator or PV, power transmission costs they would have to invest in to replace us.
If we had a voice we would not have to shut down California's economy and supply chain to be heard. But I don't think anything less would grab their attention. Laws and tariffs are are bought and paid for by special interests.
What was actually approved by PUC earlier this year was a plan to charge us cash for the power we deliver, but there was enough uproar they backed off to something more reasonable. It probably still doesn't reflect the avoided cost of infrastructure, however.
They will resume slowly cooking us frogs in the future. Already, new home purchasers are required to buy PV and supply power to PG&E at a net financial loss.
Hedges
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Rooftop PV costs $3 to $4/W installed.
Utility scale costs $1/watt.
Not sure the cost of community solar, which is an alternative to at least some rooftop.
Storage will have a similar cost delta.
Safety, and maintenance issues too.
It would be better if we were allowed to invest in utility scale, and receive a credit on our utility bill.
Also secondary market, buy/sell shares to adjust our ownership to match our consumption, which we could change in the future.
Utility scale costs $1/watt.
Not sure the cost of community solar, which is an alternative to at least some rooftop.
Storage will have a similar cost delta.
Safety, and maintenance issues too.
It would be better if we were allowed to invest in utility scale, and receive a credit on our utility bill.
Also secondary market, buy/sell shares to adjust our ownership to match our consumption, which we could change in the future.
wattmatters
Solar Wizard
Excess rooftop PV production exported to the grid is uncontrolled and should be priced accordingly. When you sign a contract to guarantee supply in the quantity they need and when they need it, which is what wholesale producers do, then let me know.
But if a utility has to take whatever excess is left over from your own consumption, whether or not the grid needs it, then frankly it's not worth nearly as much as a grid generation source with firmed supply contracts.
wattmatters
Solar Wizard
I guess it's different there. Here there is little to no avoided cost of transmission (the big high voltage transmission network) and distribution (poles and wires) infrastructure by having rooftops full of PV. Those infrastructure costs are driven by the peak system load (early weekday evenings when solar PV has all but disappeared) and the general growth of towns and cities.
The rules are changing here, where power distribution companies will be permitted to begin introducing wholesale tariff structures which do place a charge on exported rooftop PV energy. In general these wholesale tariffs won't result in actually being charged to export at retail level, but rather there will be retailer adjustments to feed-in tariffs.
And it's a good thing because the distributors who do introduce such tariffs will be required to:
(i) invest more to ensure the grid can accept more rooftop PV energy, and
(ii) reduce the tariffs charged for energy we import from the grid.
Here the distributors are pretty tightly regulated, and their incomes are a set level over five year periods. IOW it's a zero sum game for them, so by removing impediments for them to invest to enable more distributed energy supply is a good move as our ageing coal power fleet retires.
It is also fairer because at present the cost burden for the distribution network's development and maintenance is being unfairly shifted from those with solar PV to those without it, even though they all use the same infrastructure. 99%+ of solar PV here is grid-tied and they all need the same poles and wires as the non-solar homes and businesses. Off-grid is very niche, as are grid tied batteries (far too expensive).
timselectric
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The game is constantly changing. And that's why I am folding my cards and walking away from the table.
Warpspeed
Solar Wizard
Not to mention the privately owned power utilities need to show a profit, and produce a dividend for investors.
Only way to do that these days is by continually tweaking the rules and the tariffs.
The bought and paid for politicians are fully on board with that concept.
The idea that 90% of (grid tied) consumers can all arrange things so they have to pay nothing to the power utility is never going to happen.
The general belief among the uninformed general public seems to be, that fitting a grid tie system will have a payback period of X years, then after that, the power is virtually free.
Only way to win is to give the power utilities the middle finger and go completely off grid.
They will eventually have an answer for that too.
Making any solar completely illegal wherever a grid connection is available.
Only way to do that these days is by continually tweaking the rules and the tariffs.
The bought and paid for politicians are fully on board with that concept.
The idea that 90% of (grid tied) consumers can all arrange things so they have to pay nothing to the power utility is never going to happen.
The general belief among the uninformed general public seems to be, that fitting a grid tie system will have a payback period of X years, then after that, the power is virtually free.
Only way to win is to give the power utilities the middle finger and go completely off grid.
They will eventually have an answer for that too.
Making any solar completely illegal wherever a grid connection is available.
Hedges
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Maybe like education in the U.S.
We pay for public education system with our taxes.
Majority of the funds go to people and buildings that aren't used for actually teaching children.
Local property taxes provide better funding for schools in good neighborhoods, so children are bussed to different neighborhoods.
Those with money pay for private school, as well as paying for public schools.
Which sounds exactly like health care in the U.S. (or at least in California, which has its own health insurance mandate regardless of Obamacare.)
I predict in the future we will have to pay PG&E our fair share of its costs, however unreliable the grid may become. Those with money will also put in private systems.
I might do a zero-export system with batteries, although being allowed to dump surplus into the grid, even for zero credit, is better than having to carefully curtail (e.g. for guerilla solar)
We pay for public education system with our taxes.
Majority of the funds go to people and buildings that aren't used for actually teaching children.
Local property taxes provide better funding for schools in good neighborhoods, so children are bussed to different neighborhoods.
Those with money pay for private school, as well as paying for public schools.
Which sounds exactly like health care in the U.S. (or at least in California, which has its own health insurance mandate regardless of Obamacare.)
I predict in the future we will have to pay PG&E our fair share of its costs, however unreliable the grid may become. Those with money will also put in private systems.
I might do a zero-export system with batteries, although being allowed to dump surplus into the grid, even for zero credit, is better than having to carefully curtail (e.g. for guerilla solar)
Warpspeed
Solar Wizard
Hedges
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Yes, but when we move from tabulating usage during time-of-use hours to minute by minute, even an electric heater cycling on and off while PV generation is constant no longer averages out.
Perhaps variable speed mini-split can be adjusted to remain just shy of export.
Dimmer circuit for resistive heating loads.
It would be so much better if we and our neighbors could deliver PV at whatever constant rate, and cycle heaters and motors on and off. It averages out to uniform draw over a large number of homes. Instead, we will need continuously variable loads, or micro-cycling batteries to even it out. Money spent on technology and resources, when accounting could have accomplished the same more cost (and environmentally) effectively.
If San Jose is now its own utility with its own pricing, it could choose to not do minute by minute segregation of import/export. But I'll bet they pocket what that gives them, while buying steady power from PG&E. Maybe an apartment complex or condo association could do it. But you have to worry about deadbeat members.
Perhaps variable speed mini-split can be adjusted to remain just shy of export.
Dimmer circuit for resistive heating loads.
It would be so much better if we and our neighbors could deliver PV at whatever constant rate, and cycle heaters and motors on and off. It averages out to uniform draw over a large number of homes. Instead, we will need continuously variable loads, or micro-cycling batteries to even it out. Money spent on technology and resources, when accounting could have accomplished the same more cost (and environmentally) effectively.
If San Jose is now its own utility with its own pricing, it could choose to not do minute by minute segregation of import/export. But I'll bet they pocket what that gives them, while buying steady power from PG&E. Maybe an apartment complex or condo association could do it. But you have to worry about deadbeat members.
