New system config in Bay Area

[Willaby]

Ok just roughly, let's start with 7428 KWh + AC = say 8000 KWh. Since you have to pay $10/mo (for SDGE, not sure who serves you, so YMMV) or $120/yr = $120/$0.18/KWh ~= 667 KWh/yr. It is the minimum consumption below which you will still pay the same $120/yr. So you should be shooting for 8000-667 = 7333 KWh with the AC. Now with EV, your equation is much more complicated, because you can get onto the EV-TOU (or the equivalent in your area) plan, with very high rate during the day but much reduced between 12AM-5AM (also varies for different area) for charging. The ratio can be 3-4x. So if you can minimize your usage during the day to maximize the excess production (to bank your credits), you can use a lot more in the charging time. That calculation is much involved and personal. You need to check with your utility to figure out what's best for you. Personally I pushed my usage (with timers) as much as possible into the off-peak and super off-peak rates so I was able to use >1.5x of what I generated, and still just pay the minimum last year. In fact, I left about $250 on the table at true-up time.

Your thinking works for the present. The $10/month, is fairly immaterial weighed against +$200/month bills and I believe the Climate credits offset that down to ~$80/year (true?). But regardless, degradation of .5%/year will even this in a few short years. Your $250 on the table would diminish, all else equal.

More important for the future: TOU periods shifting later do not favor systems sized less than actual usage. There are many scenarios that show larger systems are optimal. Picture a household+EV using 30kw per day AND generating exactly 30kw per day, but with a peak from 4-10pm. Say the usage is spread as: 10kw super-off (EV), 10kw off-peak, and 10kw peak. With the system generating 80% of power before 4pm those credits will accrue at just about half the rate of usage during peak and this, with the super-off, will result in a bill. In fact, I'll make a guess your $250 credit from last year will turn into a bill.

To the OP, TOU periods shifting later in California are a given, maybe in a year or two. Give careful consideration for this in your planning as it is not cost effective to add capacity later. Your size calculations of ~120% sound right to me.

[Willaby]

Check out something called L.O.C.E. ( levelized cost of electricity).

JPM - I had to look up L.O.C.E plus, doing a search of it on the forum, only your name came up using the concept. But - when rates are high enough, does it really apply? With the lowest tier rates in California typically much higher than even most states highest rate, isn't it worth it to take it all out with solar. In AZ, I believe the highest rate is ~15c and solar is still popular. I guess what I'm asking is, wouldn't LOCE better apply in states with low rates?

[sensij]

More important for the future: TOU periods shifting later do not favor systems sized less than actual usage. There are many scenarios that show larger systems are optimal. Picture a household+EV using 30kw per day AND generating exactly 30kw per day, but with a peak from 4-10pm. Say the usage is spread as: 10kw super-off (EV), 10kw off-peak, and 10kw peak. With the system generating 80% of power before 4pm those credits will accrue at just about half the rate of usage during peak and this, with the super-off, will result in a bill. In fact, I'll make a guess your $250 credit from last year will turn into a bill.

To the OP, TOU periods shifting later in California are a given, maybe in a year or two. Give careful consideration for this in your planning as it is not cost effective to add capacity later. Your size calculations of ~120% sound right to me.

It is clear you've never actually modeled the new TOU rates. Even under SDG&E's most aggressive proposals, arrays producing less than what is consumed can still offset 100% of the bill (less minimum charges, etc). Also, SDG&E is down to $35 / annually for the CA climate credit, PG&E is better at about $52. However, that is real money... it would be cash in your hand, so pretending it just offsets the minimum bill in a cost-free way is foolish.

[sensij]

JPM - I had to look up L.O.C.E plus, doing a search of it on the forum, only your name came up using the concept.

A rare typo, probably. LCOE is a very standard way to compare costs of energy sources, although like anything, there are ways to misuse it to achieve a specific outcome.

[J.P.M.]

JPM - I had to look up L.O.C.E plus, doing a search of it on the forum, only your name came up using the concept. But - when rates are high enough, does it really apply? With the lowest tier rates in California typically much higher than even most states highest rate, isn't it worth it to take it all out with solar. In AZ, I believe the highest rate is ~15c and solar is still popular. I guess what I'm asking is, wouldn't LOCE better apply in states with low rates?

1.) I believe others on this forum have uttered the phrase.
2.) But, no matter. This forum is not the only venue or place on the planet discussing energy issues. For starters, try NREL + L.O.C.E. and see what you get.
3.) The electrical rate structure being high or low in terms or the cost of power is immaterial to using any tools to evaluate cost effectiveness.
4.) It may or may not make sense to offset an entire electrical bill, or any of it, or some of it via other means. LOCE and other types of similar analysis attempt to take a reasoned approach to estimate relative costs associated with different means of supplying power to an application - in this case a home. It's a toolto help in decision making. decision aiding tool
5.) From a cost standpoint, that decision depends on the relative cost of supplying the power to the home by the various means available.

6.) LOCE is one way of many to determine the cost of supplying electricity via various means that includes all costs associated with a source over some specified period and comparing them on the same basis, which is why they are called levelized costs.
7.) LOCE is an economic tool. It may use different criteria. It is part process economics, part life cycle costing, part time value of money type analysis. It is somewhat different than other methods in that when used in energy type analyses, the costs are usually presented on a cost per kWh basis, which are not the same as the cost one pays to a POCO.

8.) See: "A Manual for Economic Evaluation of Energy Efficiency and Renewable Energy Technologies", Short, Packey and Holt , NREL/TP-462, March, 1995 for particulars. Also see NREL - SAM for some practical explanations. The SAM site will allow a user to get to a lot of other NREL stuff related to LOCE and other life cycyle analysis tools.

To answer your question: No - not necessarily, but not necessarily worse or a waste of time either. What an LOCE analysis will give is an estimate of the relative cost of supplying electricity via different means. To turn your question around, it is good anywhere an estimate of the difference in the long term cost of supplying electricity by different sources is sought. For PV, that usually is two methods - POCO power or PV. The LOCE of both are calculated and compared, including all costs for acquisition, operating, cost of funds, salvage value and other things that may or may not be deemed appropriate to the situation and analysis.

Again, the LOCE cost per kWh is NOT the same as either the POCO power cost/kWh or the system cost /expected total lifetime output. See the provided references in 8 above for details. There are also on line calculators available that seem to make the task a bit easier. I'd caution users to be careful about the assumptions some calculators use.

Take what you want. Scrap the rest.

[ltbighorn]

It is clear you've never actually modeled the new TOU rates. Even under SDG&E's most aggressive proposals, arrays producing less than what is consumed can still offset 100% of the bill (less minimum charges, etc). Also, SDG&E is down to $35 / annually for the CA climate credit, PG&E is better at about $52. However, that is real money... it would be cash in your hand, so pretending it just offsets the minimum bill in a cost-free way is foolish.

sensij, do you have any good links for estimates on the impacts of the TOU changes? I'm in the final days of sizing my system and this is definitely the most uncertain variable in my calculations, though I'm in PG&E territory.

[sensij]

sensij, do you have any good links for estimates on the impacts of the TOU changes? I'm in the final days of sizing my system and this is definitely the most uncertain variable in my calculations, though I'm in PG&E territory.

Some detailed discussion of the next generation of PG&E's TOU plans was filed here:

https://www.pge.com/nots/rates/tarif...LEC_4764-E.pdf

The TOU pilot structures they are experimenting with create a nice window through which we can see what direction they would like to go.

See also the following, which shows how the E-6 plan will evolve in 2021.

https://www.pge.com/nots/rates/tarif...LEC_4769-E.pdf

I generally recommend sizing a system such that there is a reasonable probability of it paying for itself within the first 10 years. Beyond that, no matter what rates do, your system should be a net benefit. If you size so large that it takes longer than that to recover the installation costs (for example, by buying Sunpower), the exposure to rate uncertainty is even higher and it is hard to know if the system will ever actually get into the black.

[J.P.M.]

A rare typo, probably. LCOE is a very standard way to compare costs of energy sources, although like anything, there are ways to misuse it to achieve a specific outcome.

OOPS. Make all my LOCE == LCOE's. My error and I apologize for it. Been a long day.

Sensij: Thanx for the cache

[Willaby]

OOPS. Make all my LOCE == LCOE's.

You've got some correcting to do, back a couple years. That's why the search only brought up your name

[J.P.M.]

A rare typo, probably. LCOE is a very standard way to compare costs of energy sources, although like anything, there are ways to misuse it to achieve a specific outcome.

OOPS. Make all my LOCE == LCOE's. My error and I apologize for it. Been a long day.

Sensij: Thanx for the cache

[Willaby]

It is clear you've never actually modeled the new TOU rates. Even under SDG&E's most aggressive proposals, arrays producing less than what is consumed can still offset 100% of the bill (less minimum charges, etc). Also, SDG&E is down to $35 / annually for the CA climate credit, PG&E is better at about $52. However, that is real money... it would be cash in your hand, so pretending it just offsets the minimum bill in a cost-free way is foolish.

You realize you corrected me for $5/year and you call me foolish? I think I'll stick with immaterial. Btw, the " ~ " means "approximate" since the climate credit varies. I'm gathering you don't like what I say since you were such a champion of 60% offset last year. That's not good advice today.

No, I have never actually modeled new TOU rates, haven't seen them, what are they? And, yeah, for some very few, producing less than consumed "could" offset 100% of the bill, but not likely for most.

Here's what I know. The TOU "peak" is moving, likely to 4pm and likely in the near future. TOU "off peak" rates will be less than the "peak". I mean that's the definition peak vs off-peak, right? One is higher and one is lower? What the spread will be? I don't know, but likely substantial.

Lastly, "most aggressive proposals"? for what? the next 3 or 4 years? I'm talking about a 20-25 year investment. You can barely look past a three year out proposal. Pay a little extra now to "right-size" or cry later.

[Willaby]

1.) I believe others on this forum have uttered the phrase.
2.) But, no matter. This forum is not the only venue or place on the planet discussing energy issues. For starters, try NREL + L.O.C.E. and see what you get.
3.) The electrical rate structure being high or low in terms or the cost of power is immaterial to using any tools to evaluate cost effectiveness.
4.) It may or may not make sense to offset an entire electrical bill, or any of it, or some of it via other means. LOCE and other types of similar analysis attempt to take a reasoned approach to estimate relative costs associated with different means of supplying power to an application - in this case a home. It's a toolto help in decision making. decision aiding tool
5.) From a cost standpoint, that decision depends on the relative cost of supplying the power to the home by the various means available.

6.) LOCE is one way of many to determine the cost of supplying electricity via various means that includes all costs associated with a source over some specified period and comparing them on the same basis, which is why they are called levelized costs.
7.) LOCE is an economic tool. It may use different criteria. It is part process economics, part life cycle costing, part time value of money type analysis. It is somewhat different than other methods in that when used in energy type analyses, the costs are usually presented on a cost per kWh basis, which are not the same as the cost one pays to a POCO.

8.) See: "A Manual for Economic Evaluation of Energy Efficiency and Renewable Energy Technologies", Short, Packey and Holt , NREL/TP-462, March, 1995 for particulars. Also see NREL - SAM for some practical explanations. The SAM site will allow a user to get to a lot of other NREL stuff related to LOCE and other life cycyle analysis tools.

To answer your question: No - not necessarily, but not necessarily worse or a waste of time either. What an LOCE analysis will give is an estimate of the relative cost of supplying electricity via different means. To turn your question around, it is good anywhere an estimate of the difference in the long term cost of supplying electricity by different sources is sought. For PV, that usually is two methods - POCO power or PV. The LOCE of both are calculated and compared, including all costs for acquisition, operating, cost of funds, salvage value and other things that may or may not be deemed appropriate to the situation and analysis.

Again, the LOCE cost per kWh is NOT the same as either the POCO power cost/kWh or the system cost /expected total lifetime output. See the provided references in 8 above for details. There are also on line calculators available that seem to make the task a bit easier. I'd caution users to be careful about the assumptions some calculators use.

Take what you want. Scrap the rest.

Ok, thanks. For me 80% was I just wanted to know what it costs over the life, how long it takes to pay back and what is the rough rate of return. Maybe that's incorporated into your LCOE, or partially. Or maybe if I did full LCOE analysis I would have chucked the whole thing.

[J.P.M.]

You've got some correcting to do, back a couple years. That's why the search only brought up your name

I may, but right now I'm busy looking for ways to get the egg off my face.

Seriously, poor communication and worse proof reading. I expect better.

[sensij]

Lastly, "most aggressive proposals"? for what? the next 3 or 4 years? I'm talking about a 20-25 year investment. You can barely look past a three year out proposal. Pay a little extra now to "right-size" or cry later.

Your ignorant ranting is hard to follow. I didn't make a $5 correction to what you wrote... you completely misrepresented the CA climate credit as a bill offset... it offsets the bill in exactly the same way as money in your checking account. Saying "my bill is less because of the climate credit" is akin to saying "my bill is less because I just paid it". In either case, money that could have been spent on something else is spent on the electric bill, a portion of the bill that cannot be offset cost effectively by solar.

You make your 25 year investment. I'll make a series of 5 to 10 year investments, each appropriate for the circumstances at that time using the most cost effective technology. We will see who comes out ahead.

[Willaby]

Your ignorant ranting is hard to follow. I didn't make a $5 correction to what you wrote... you completely misrepresented the CA climate credit as a bill offset... it offsets the bill in exactly the same way as money in your checking account. Saying "my bill is less because of the climate credit" is akin to saying "my bill is less because I just paid it". In either case, money that could have been spent on something else is spent on the electric bill, a portion of the bill that cannot be offset cost effectively by solar.

You make your 25 year investment. I'll make a series of 5 to 10 year investments, each appropriate for the circumstances at that time using the most cost effective technology. We will see who comes out ahead.

Ahh, the name calling since you don't like what I say, but I'll refrain from stooping. I indicated "true?" regarding the credit because I wasn't sure and don't have my bill at hand or if the credit would actually be paid if there was no bill. It's not enough to matter. The whole $10/month is immaterial. It is 5% of my bill.

What is your bill today and what do you expect it to be five years from now. "a series of 5 to 10 year investments", really?, now that's a new one. I'm afraid to ask.