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Whats more energy efficient: Off-grid or Grid-tie ?

It all depends on where you decide to say the grid power starts at, some distant dam, solar farm in the next state, a coal burning plant, a nuke somewhere, or sometimes it impossible to determine. For example, Los Angeles may import hydro power from Hoover Dam or the Pacific Inter-tie which sources power from Washington.
In the end efficiency isn't the big question, what it costs you is.
 
In the end efficiency isn't the big question, what it costs you is.
Right, which is why most folks use financial efficiency as a determining factor in their decision to invest in solar, batteries, energy efficiency upgrades, insulation, electric cars, etc.

Honestly I don’t care a lot about the PoCo ‘s financial efficiency, and I only have a theoretical concern for the rest of the ratebase who is picking up the tab.

If my investment in solar power stuff (and the installation and maintenance thereof) pays off in 5-10 years then it’s worthwhile. If not I’ll keep the money in the bank and use the interest to pay my power bills and other expenses. Simple self interest (if you see what I did there), that’s how most consumers work.

I’m also not surprised when they change the rules, my grid-tied stuff is paid off and battery prices are way down, so I’ll pivot to mostly-off-grid.
 
It all depends on where you decide to say the grid power starts at, some distant dam, solar farm in the next state, a coal burning plant, a nuke somewhere, or sometimes it impossible to determine. For example, Los Angeles may import hydro power from Hoover Dam or the Pacific Inter-tie which sources power from Washington.
Which is why all you can ever actually do is deal with system averages given the grid is one very large and complex machine. Power generators knows how much is fed in, and consumption meters know how much is consumed. The difference is losses.
 
Right, which is why most folks use financial efficiency as a determining factor in their decision to invest in solar, batteries, energy efficiency upgrades, insulation, electric cars, etc.
It's an important factor, although not the only one.

Honestly I don’t care a lot about the PoCo ‘s financial efficiency
I do to a certain extent. It has a direct impact of the standard of service delivery. Distributors here have a regulated revenue cap. So the more efficient they are, the better they perform for the customer.

But they do need to learn to embrace and adapt to increasing levels of distributed generation.
 
Physical efficiency and financial efficiency are different
Yes, I did clarify in my post that from a revenue model grid tie was more efficient and that was my main point. For that reason I only care about the kWhs in and out of the meter because grid efficiency does not impact the financial efficiency of those kWhs.
 
Yes, I did clarify in my post
Yes, I was just emphasising it.

Always good to keep in mind that financial efficiency can change at the stroke of a pen. Physics however is immutable.

I would not mind that in the USA if we could get solar installed in the USA as inexpensive as in Australia.
Yep, which is why the US needs to sort out the mess of non-standard regulatory requirements/approvals/restrictions.
Approvals which take months? That's nonsense.
Legal road blocks for installing off-grid systems? More nonsense.

It stifles what could be a very efficient industry.

It's a curious anomaly as pretty much any other tech is more expensive here than there, a function of lower scale (smaller market of 26 M people) and distance from source.
 
Approvals which take months?
That was not the case in my Owner builder permit. It took less than ten days.
Yep, which is why the US needs to sort out the mess of non-standard regulatory requirements/approvals/restrictions

The California market is probably bigger than the entire Australian market and regulations/approvals/restrictions are fairly consistent througout the state so I am not sure that is the issue. I wish it were as simple as you suggest.
 
It depends. While appreciating the academic points on conversion losses that you're raising on it, my take is this.

  • Selling at wholesale and having to buy back overnight at retail is fiscally inefficient.
  • Downtime during a grid outage is 100% inefficient.
  • You can't guarantee 1:1 will remain an option.

Compared with the above, loss in conversion is less a concern when you're generating it for free.
 
Hello Meetyg,

Off-grid would be way more energy efficient as you don't incur the losses in transporting the electricity to the same extent, much of that transportation would require transformers and in some instances, where we use high voltage DC lines, changing from AC to DC and back to AC would also be required. DC coupled solar to the battery is fairly efficient and turning solar or battery into AC to feed the house, the grid or both, is a loss you'd incur regardless if comes from battery or solar. Even AC coupled with your battery would likely be more efficient depending on the system you use and the distance the electrons would have to travel.
 
Off grid is probably more efficient for a home user or small business. Net metering is not economically viable long term and was only used as an incentive. It's unclear how to quantify the useful gain your small system is providing the power grid, but you can quantify the amount of useful energy your system provides to you. If you want to sell power to the grid, become a small (100 kw+) PV power provider as a business. The returns are better and the only way it makes sense financially or technically. I predict net metering will be extinct in 5-10 years anyway.

There are many reasons to lessen dependence on the power company, and the cost of building a truly capable off grid or hybrid system keeps dropping.
 
Off grid is probably more efficient for a home user or small business.
That really depends on many factors.

One of the issues with off-grid is the need to provision a sizeable over-capacity of PV and storage because you need to account for the periods of poor output, so you end up with a lot of unrealised generation capacity when the solar conditions are good for production and more storage than you need for most daily needs. The grid overall is far better at balancing supply and demand.

Off-grid is like the Pareto principle. 80% of the cost goes into covering the last 20% of demand. Often a blended system is more cost effective, use the grid to cover that difficult 20%.

For us to go off-grid I would need to quadruple generation capacity, sextuple our storage, and at least double inverter capacity.

Net metering is not economically viable long term and was only used as an incentive.
By that you mean net metering with an import:export tariff ratio of 1:1. The ratio does not need to remain at 1:1.

Here the export tariff is a small fraction of the import tariff. That's because generation is equivalent to the wholesale value of the energy (which during the day here is cheap as chips), while imported energy carries the cost of transmission and distribution.

Even that is changing, from 1 July in my state the energy distributors will begin to levy a charge on exports above a given free threshold between 10AM-3PM. But they are also offering an additional incentive for exports in the late afternoon/evening peak period.
 
My strategy for cost recovery is a mixed system. Originally I designed the system as a hybrid, but later changed to a manually swiched subpanel powered by the PV / Inverter / Batteries. From that subpanel I can run the AC, major appliances, and 2 or 3 rooms. No grid interaction.
 
That really depends on many factors.

One of the issues with off-grid is the need to provision a sizeable over-capacity of PV and storage because you need to account for the periods of poor output, so you end up with a lot of unrealised generation capacity when the solar conditions are good for production and more storage than you need for most daily needs. The grid overall is far better at balancing supply and demand.

Off-grid is like the Pareto principle. 80% of the cost goes into covering the last 20% of demand. Often a blended system is more cost effective, use the grid to cover that difficult 20%.

For us to go off-grid I would need to quadruple generation capacity, sextuple our storage, and at least double inverter capacity.


By that you mean net metering with an import:export tariff ratio of 1:1. The ratio does not need to remain at 1:1.

Here the export tariff is a small fraction of the import tariff. That's because generation is equivalent to the wholesale value of the energy (which during the day here is cheap as chips), while imported energy carries the cost of transmission and distribution.

Even that is changing, from 1 July in my state the energy distributors will begin to levy a charge on exports above a given free threshold between 10AM-3PM. But they are also offering an additional incentive for exports in the late afternoon/evening peak period.
I agree.
I currently only have 5kwh of storage.
On one hand, I want to have enough capacity should a prolonged grid outage occur.
On the other hand, if I want to make good use of my PV during sunny days, I will need to deplete my batteries to around 10% SOC.

As for PV, I guess I have enough to fully charge the battery every day (during peak seasons), but during off-peak seasons or the occasional cloudy days, it's not enough.

I am planning to increase my PV in the future (a but limited by physical space, maybe go bi-facial). Same for battery storage.
But for now I'm trying to get the most out if my existing system.
 
1:1 net metering has 100% financial efficiency.
For the homeowner. As a matter of public policy, we force the financial losses onto the power company (and their ratebase), which was useful to encourage residential solar, but the pendulum is starting to swing the other way.

Also, when the first serious residential R.E. systems were going in, deployed residential meters were mostly the 1:1 mechanial models, so no change was required, while the solar and wind power tended to shave, rather than accentuate, load peaks, so the cost to the utilities of their line-losses was cheaper than the more expensive peaking-power generation and their magnitude wasn't enough to destabilize the grid. So the utilities weren't hurting finantially (though they still didn't like it).

As residential R.E. grew to become a major part of the generation, though, it became enough of a problem and mismatch for the load curve that the utilities (since they couldn't make it go away) wanted to go toward a "sell power at retail, buy at wholesale, charge separately for the grid infrastructure, penalize destabilization" model. And smart meters were becoming cheap enough that replacing all the meters to achieve this was practical. (Well, actually they wanted to get all the traffic would bear, but knew they had to settle for something plausible to get past the government regulators and customer reaction.)

Note that another reason for a utility to put in a smart meter is to defeat some power stealers, who would pull a meter and reinsert it upside-down for part of the month, to make it count their power use back down. If they put it back to normal orientation soon enough, and if the meter reader didn't notice the broken seal, the only way the power company would notice was if they used more power with it upside down and it showed a negative use for the month. To defeat this, smart meters are normally programmed to count power as "used", to be paid for" no mater which way it goes. So their configuration has to be changed, or the meter replaced with one set up for net metering, for net to be billed correctly. Thus you have to inform the company, which also lets them know to come check your installation meets their standards and isn't too big for your drop or an islanding lineman--killer.
 
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What's happening here is daytime tariffs are falling - it's now increasingly common for there to be free energy tariff options during the middle of the day.

Indeed I have a plan which is a bit like that. 12-2PM on weekends is free, so my batteries are programmed to charge at max rate from the grid during that period. As is the EV. But there is another retail plan where the tariff is zero 11AM-2PM every day. You can suck a fair bit of energy down in three hours if you have storage. For us that's the EV, the water heater and the off-grid home battery.

There are also wholesale pass through plans which, if you have good energy management automation, can result in much lower costs overall, but they do require more care as there are downside risks as well. Certainly during periods of negative wholesale tariffs you can be paid to consume.

None of this is possible without smart meters.
 
The power company where I live in North Carolina just started a plan where they will give anyone with a qualifying ESS system a monthly bill credit for the right to use your ESS system a certain number of times a year to support the grid in emergency situations. They have to send you a request ahead of time and you are allowed to say no a certain number of times a year. And to be clear, you get the credit every month whether they actually use it or not. They are basically paying you every month to have the option to use it. And unlike net metering credits that can only offset other power usage, these credits can offset any charge including taxes and fixed charges. And if you accumulate a negative balance, you can request they send you a check.

The amount of the credit is based on the KW's your system can produce to support the grid. As an example, a single Powerwall 3 which can generate 11.4k of power back to the grid gets you a $54 a month credit. The plan will allow up to $600 a month in credits. They don't care how many KWH of energy storage you ESS has. So clearly this is for very short-term support of the grid.

This is speculation on my part, but I suspect a strong motivation of this plan is grid Black Start scenarios where they can need as much as 2x the normal KW to be able to restart the grid after a black out. But I'm sure it can also help them for transient load spikes. In the winter on workdays when there's are big storms, I bet they get big spikes in demand at the typical wake up time for people.
 
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