Is there any benefit to changing the date for your permission to operate?

[J.P.M.]

No apologies necessary, really. Perhaps one of the things that keeps my AC usage down is I have planted a fair amount of foliage around the house and keep it trimmed. Additionally, I installed Coolaroo window sun shades on all my south and west facing windows. Those help a lot. I ended up replacing the HVAC unit in 2016 and while not the most efficient at the time, it's much better than before (I think it's a SEER 16 rating).

I'm currently on the domestic tiered plan and I'm sure TOU will affect things going forward. Which begs the question of which TOU plan to select. Ideally a battery (like a Powerwall) would help offset some of the peak rates, but I'm not in a position to afford one of those right now,

Understood.

Kudos on lots of heads' up work on reducing A/C load.

On the Coolaroo shades: Interior or exterior ?

Not bad, but not the best news: Finding best rate plan is never an easy task. It also involves more assumptions about the future that increase the uncertainty of the analysis which is impossible to know with a lot of certainty in the first place. Still, some homework and a few hours of reading up on POCO rates/policies can yield useful information.

To do it right - that is, to do an analysis of use vs. available rates that shows as much of the information as necessary for an informed choice about which rate plane is likely to have the highest probability of the lowest cost of providing future electrical service for your chosen length of time into the future - is right up front - a PITA. A big part of the PITA is the necessity of doing a deep dive into the POCO rate policies and plans. I haven't found a way around that yet that gives as reliable results.

Take what you what of the following.

The overview:
1.) Decide what your future electrical use is likely to be to meet your future goals. Get as granular as you can. Ideal would be 15 minute increments. Such historical info is available from the POCO. Often, using such historical usage data and then adding estimates/SWAGs of possible future changes/increments to those 15 minute use numbers might improve the guesswork from SWAG to educated dart throw status. Combine the 15 minute data to 1 hour increments. You'll lose a slight amount of accuracy in doing so, but it's all an est. to begin with. Put that data on a spreadsheet.
2.) Use the PVWatts hourly output option to estimate system output. That data is all on standard time. Correct the PVWatts data for daylight savings time. Put that data on the spreadsheet making sure the hourly times line up. The spreadsheet will have 8,760 rows of hourly data, one for each hour of the year.
3.) Subtract generation from use.
4.) Multiply each hour's net draw (either + or -) by the electricity rate for that hour.
5.) Sum the net draw per billing period.

Do that for each rate plan under consideration and choose the one that suits your fancy - I'd guess the one that results in the lowest annual bill.

There may be and probably are easier ways to do it, but since I'm pretty ignorant about spreadsheets, that method, with a few additional minor points I've left out for the sake of brevity, but don't affect the outcome much, works for me. There's also a lot of repetition/copying in the spreadsheet 's creation which saves time.

[loungelizard]

I got confused about your location. Had it in my head you were in Orange co. for some B.S. reason. Apologies.

I appreciate living in the Coachella Valley. I'm currently living in 92026, but I owned/lived at PGA West for a few years. The POCO there is the Imperial Valley H2O district and their rates were almost dirt cheap compared to SCE, at least when I lived there.

Actually, your annual use (not billing) is a lot lower than most other single family units in the Coachella valley, even, and maybe particularly in the summer. My AC there burned through ~ 1,300 - 1,600 kWh/month in summer depending mostly on ave. ambient temp. Anecdotally, my summer use was a lot lower than my neighbors, but the low electric rates and deep pockets of my neighbors probably had something to do with their high(er) consumption.

The combination of T.O.U. rates in general and A/C loads (mostly because of the peak time schedules associated with T.O.U. rates correspond to the times of most likely A/C use) usually add up to large(r) electric bills than when on a tiered rate.

Don't know what rate schedule you're on, but if you are not already, you'll be on some form of T.O.U. rates after the PV addition, and you'll probably get to choose among some options. Not all rate plans produce the same bills. It often pays to do the PITA homework and run bills for different plans as f(expected/estimated future use/patterns), keeping in mind that things/billing options/mandates will probably change at some point(s).

FWIW, as much as it seems like a no brainer and not withstanding how good it may feel good to tell the POCO to cram their power, for cost effectiveness considerations (only), at least in the past, and still at this time, the most long term cost effective system PV system usually works out to be one that does not offset 100% of an electric bill.

Long story short, and assuming at least one reason for getting PV in the first place is to have a lower electric bill, if solar process economics are used to find the PV size that results in the lowest long term cost of providing electric service to a residence, that system size is usually one that offsets < 100 % of an electric bill.

No apologies necessary, really. Perhaps one of the things that keeps my AC usage down is I have planted a fair amount of foliage around the house and keep it trimmed. Additionally, I installed Coolaroo window sun shades on all my south and west facing windows. Those help a lot. I ended up replacing the HVAC unit in 2016 and while not the most efficient at the time, it's much better than before (I think it's a SEER 16 rating).

I'm currently on the domestic tiered plan and I'm sure TOU will affect things going forward. Which begs the question of which TOU plan to select. Ideally a battery (like a Powerwall) would help offset some of the peak rates, but I'm not in a position to afford one of those right now,

[J.P.M.]

Hmmm...I'm going to have to look at my compressor and get more numbers. I actually find this whole this fascinating trying to nail this down.

I'm actually in the Palm Springs area and I've done most I can to lower my energy usage (LED bulbs everywhere, insulation etc etc). In the winters, I use around 330-350 kWh per month. Then summer hits and last July I used 1,334 kWh for example. One reason I might be higher than others is because I work from home.

I think, at this point, it's better for me to overestimate that under. Right now Edison is charging 20 cents/Kwh for the lowest baseline level and I would would eventually like to get to completely energy independent with the house and car.

I got confused about your location. Had it in my head you were in Orange co. for some B.S. reason. Apologies.

I appreciate living in the Coachella Valley. I'm currently living in 92026, but I owned/lived at PGA West for a few years. The POCO there is the Imperial Valley H2O district and their rates were almost dirt cheap compared to SCE, at least when I lived there.

Actually, your annual use (not billing) is a lot lower than most other single family units in the Coachella valley, even, and maybe particularly in the summer. My AC there burned through ~ 1,300 - 1,600 kWh/month in summer depending mostly on ave. ambient temp. Anecdotally, my summer use was a lot lower than my neighbors, but the low electric rates and deep pockets of my neighbors probably had something to do with their high(er) consumption.

The combination of T.O.U. rates in general and A/C loads (mostly because of the peak time schedules associated with T.O.U. rates correspond to the times of most likely A/C use) usually add up to large(r) electric bills than when on a tiered rate.

Don't know what rate schedule you're on, but if you are not already, you'll be on some form of T.O.U. rates after the PV addition, and you'll probably get to choose among some options. Not all rate plans produce the same bills. It often pays to do the PITA homework and run bills for different plans as f(expected/estimated future use/patterns), keeping in mind that things/billing options/mandates will probably change at some point(s).

FWIW, as much as it seems like a no brainer and not withstanding how good it may feel good to tell the POCO to cram their power, for cost effectiveness considerations (only), at least in the past, and still at this time, the most long term cost effective system PV system usually works out to be one that does not offset 100% of an electric bill.

Long story short, and assuming at least one reason for getting PV in the first place is to have a lower electric bill, if solar process economics are used to find the PV size that results in the lowest long term cost of providing electric service to a residence, that system size is usually one that offsets < 100 % of an electric bill.

[Ampster]

Without more details, your 4.6 kW choice to offset ~ 7,700 kWh/yr. looks about right for So. CA for a decently oriented system (that'll produce very approx. 1600 - 1750 or so kWh/yr. per installed STC kW for an unshaded array).

In the future a TOU rate may give you a benefit depending on your usage patterns and your ability to shift loads. More on that below in the EV discussion.

For adding an EV: Depending on size and how it's driven, folks who own them tell me an EV will require something like 300 - 350 or so kWh for every 1,000 miles driven.
Ampster and other EV owners may well be more informed than I am on that issue. My info on that is little more than informed hearsay, but, FWIW, seems pretty consistent.

300-350 kWh for every 1,000 miles is a good estimate. One of my EVs is more efficient so my earlier estimate was based on 250 kWh per 1,000 miles. An EV is one of the easiest ways to load shift and leverage TOU rates. I have had EVs as long as I have had solar and have always opted for TOU rates. As I mentioned earlier in this thread I use a lot of energy at super off peak rates ($0.15/kWh) and get credited at peak and shouldr peak rates in excess of $0.30/kWh so that is the load shifting and leverage I was referring to. Some of it is discretionary because I have one other free source and many others that charge about $0.20/kWh. I can go into more details if the OP is interested.

On lowering A/C temp. and its effect on electricity usage: Without a lot of particulars about local climate and use patterns, that's be hard to est. I'm close to you in annual total usage, ~ 7,200 - 7500 kWh/yr, but I'm probably in a different temp. climate (I'm a bit warmer ?) than you are.

As you write, I usually run my A/C at ~78 F., but I ventilate heavily at night which helps reduce the run time and so A/C use by ~ 20-25 %. The A/C compressor runs between ~ 175 and 190 or so hrs./season. It's a 5 ton (60,000 BYU/hr.) system that draws 6 kW when running steady state, including blower motor. My average seasonal A/C use chews through ~ 1,050 - 1,150 kWh/A/C per season including the blower draw. If I lower the thermostat, the best/approx. estimate: Very approximately, every deg. F. I lower the thermostat increases the annual A/C draw by about 150 kW/yr or so. Your results will most definitely be different. Offered as anecdotal info only.

I find it harder to quantify the benefit of a degree or two in my AC setting but I generally also set mine to 78 degrees. I also ventilate in the evening and early morning and have recently installed an attic fan that may make a few degrees difference in the attic temperature.

[loungelizard]

Without more details, your 4.6 kW choice to offset ~ 7,700 kWh/yr. looks about right for So. CA for a decently oriented system (that'll produce very approx. 1600 - 1750 or so kWh/yr. per installed STC kW for an unshaded array).

For adding an EV: Depending on size and how it's driven, folks who own them tell me an EV will require something like 300 - 350 or so kWh for every 1,000 miles driven.

Ampster and other EV owners may well be more informed than I am on that issue. My info on that is little more than informed hearsay, but, FWIW, seems pretty consistent.

On lowering A/C temp. and its effect on electricity usage: Without a lot of particulars about local climate and use patterns, that's be hard to est. I'm close to you in annual total usage, ~ 7,200 - 7500 kWh/yr, but I'm probably in a different temp. climate (I'm a bit warmer ?) than you are.

As you write, I usually run my A/C at ~78 F., but I ventilate heavily at night which helps reduce the run time and so A/C use by ~ 20-25 %. The A/C compressor runs between ~ 175 and 190 or so hrs./season. It's a 5 ton (60,000 BYU/hr.) system that draws 6 kW when running steady state, including blower motor. My average seasonal A/C use chews through ~ 1,050 - 1,150 kWh/A/C per season including the blower draw. If I lower the thermostat, the best/approx. estimate: Very approximately, every deg. F. I lower the thermostat increases the annual A/C draw by about 150 kW/yr or so. Your results will most definitely be different. Offered as anecdotal info only.

Hmmm...I'm going to have to look at my compressor and get more numbers. I actually find this whole this fascinating trying to nail this down.

I'm actually in the Palm Springs area and I've done most I can to lower my energy usage (LED bulbs everywhere, insulation etc etc). In the winters, I use around 330-350 kWh per month. Then summer hits and last July I used 1,334 kWh for example. One reason I might be higher than others is because I work from home.

I think ,at this point, it's better for me to overestimate that under. Right now Edison is charging 20 cents/Kwh for the lowest baseline level and I would would eventually like to get to completely energy independent with the house and car.

[J.P.M.]

OK, this helps me out. Again, newbie, I'm still learning some of the nuances. Last year I used 7,726 kWh from Edison. I've been all over PVWatts with this and I'm coming up with a 4.6 kW system to cover my basic usage. If I oversize to accommodate an EV, I'd add 1,000 watts which would take my system up to about a 5.2 kW system.

Now the only big remaining variable is that I would always set my thermostat to 78 degrees in the summer (I'm in the desert here in SoCal). Not ideally the temperature I would like. I'd prefer 75-76 so I just need to somehow factor that it as well.

Without more details, your 4.6 kW choice to offset ~ 7,700 kWh/yr. looks about right for So. CA for a decently oriented system (that'll produce very approx. 1600 - 1750 or so kWh/yr. per installed STC kW for an unshaded array).

For adding an EV: Depending on size and how it's driven, folks who own them tell me an EV will require something like 300 - 350 or so kWh for every 1,000 miles driven.

Ampster and other EV owners may well be more informed than I am on that issue. My info on that is little more than informed hearsay, but, FWIW, seems pretty consistent.

On lowering A/C temp. and its effect on electricity usage: Without a lot of particulars about local climate and use patterns, that's be hard to est. I'm close to you in annual total usage, ~ 7,200 - 7500 kWh/yr, but I'm probably in a different temp. climate (I'm a bit warmer ?) than you are.

As you write, I usually run my A/C at ~78 F., but I ventilate heavily at night which helps reduce the run time and so A/C use by ~ 20-25 %. The A/C compressor runs between ~ 175 and 190 or so hrs./season. It's a 5 ton (60,000 BYU/hr.) system that draws 6 kW when running steady state, including blower motor. My average seasonal A/C use chews through ~ 1,050 - 1,150 kWh/A/C per season including the blower draw. If I lower the thermostat, the best/approx. estimate: Very approximately, every deg. F. I lower the thermostat increases the annual A/C draw by about 150 kW/yr or so. Your results will most definitely be different. Offered as anecdotal info only.

[loungelizard]

...


Most NEM agreements allow you to increase the system size by the greater of 10% or 1000 Watts but that should not be your only decision factor. Using a rough rule of thumb 1000 Watts would only generate enough energy to drive a small EV 5,000 to 7,000 miles a year. That estimate has more to do with location than the efficiency of any particular EV. More importantly the cost per Watt of adding 1000 Watts a year or two later would probably be more than adding 2000 Watts to your system initially unless you were going to do it yourself. Essentially the larger a system the less you should have to pay per Watt for a system. That is why my previous applications were always based on assumptions of energy rate increases and energy usage increases. I did not include the things I was going to do to use energy more efficiently. The modest reduction in return by oversizing those systems has paid off for me on several occasions. As I often have said, it all depends on where you are standing and your mileage may vary.

OK, this helps me out. Again, newbie, I'm still learning some of the nuances. Last year I used 7,726 kWh from Edison. I've been all over PVWatts with this and I'm coming up with a 4.6 kW system to cover my basic usage. If I oversize to accommodate an EV, I'd add 1,000 watts which would take my system up to about a 5.2 kW system.

Now the only big remaining variable is that I would always set my thermostat to 78 degrees in the summer (I'm in the desert here in SoCal). Not ideally the temperature I would like. I'd prefer 75-76 so I just need to somehow factor that it as well.

[Ampster]

The that's the part that gets me because as I understand Edison, it's use it or lose it in 12 months.

That is true for most NEM agreements which calculate TrueUp cash payouts at wholesale rates.

In fact, I needed to sign a document from Edison saying I wouldn't overproduce

I have been through 3 PTOs and my interpretation is you are not being asked to say you won't overproduce. What you are being asked to certify is that your request (the application) for a system of a particular size was based on a reasonable assumption. If the weather was clear and cold for 365 days you would overproduce and there would be nothing they could do about that. An EV or two in the future is a reasonable assumption. It is also reasonable, based on my experience, that once you get an EV you may like driving it so much that you could reasonably put more mileage on it than you did with your noisy smelly gasoline powered car(s). Two of my applications for PTOs were done within months of purchasing those homes and I had to make assumptions. When you get your NEM agreement, it will specify the system size and inverter size. That is what you are agreeing to. The NEM agreement is the contract, not the application.

So, if I would like to get an EV in the future, say 12-24 months, I should size accordingly. This is what I'm trying to do, but in the meantime, I would be overproducing and receiving nothing for it. I suppose, it is what it is.

Yes it is a classic financial hedging question,
Most NEM agreements allow you to increase the system size by the greater of 10% or 1000 Watts but that should not be your only decision factor. Using a rough rule of thumb 1000 Watts would only generate enough energy to drive a small EV 5,000 to 7,000 miles a year. That estimate has more to do with location than the efficiency of any particular EV. More importantly the cost per Watt of adding 1000 Watts a year or two later would probably be more than adding 2000 Watts to your system initially unless you were going to do it yourself. Essentially the larger a system the less you should have to pay per Watt for a system. That is why my previous applications were always based on assumptions of energy rate increases and energy usage increases. I did not include the things I was going to do to use energy more efficiently. The modest reduction in return by oversizing those systems has paid off for me on several occasions. As I often have said, it all depends on where you are standing and your mileage may vary.

[loungelizard]

Caveat with all of this net billing/trueup date/NEM particular interplay:
...Note however, and be careful: If the excess generation credit disappears after an additional 12 billing period carryover, congratulations - you own an oversized, less than optimally cost effective system. You options are then to burn off the excess generation by using it for tasks now done by other means, or leave the lights on, the A/C running or get an EV or something else you might not need to do or have planned on.

The that's the part that gets me because as I understand Edison, it's use it or lose it in 12 months. In fact, I needed to sign a document from Edison saying I wouldn't overproduce.oversize.pngSo, if I would like to get an EV in the future, say 12-24 months, I should size accordingly. This is what I'm trying to do, but in the meantime, I would be overproducing and receiving nothing for it. I suppose, it is what it is.

[J.P.M.]

Caveat with all of this net billing/trueup date/NEM particular interplay:

While NEM is easy to understand in concept, and most POCOs have some form of NEM, it's probably safe to say that while they are similar, they are all different enough in ways that can make blanket statements and assumptions that make understanding of your particular POCO's NEM policies necessary if you're serious about picking a trueup date. One method most likely does not fit all or even maybe most POCO's NEM policies. That may well also apply to possible best methods for different rate plans within the same POCO.

In most any case however, for the knowledge gained for what's probably a relatively small cost, I'd agree that waiting 12 months (or ore) if given the choice makes sense, and see how your generation amount and pattern compares with your usage amount and patterns.

That said, some general statements MAY be applicable.

Unless a system is grossly oversized, for most NEM situations, we're not talking huge amounts of money here. Still, a comparison of your system size (and so annual generation) relative to usage may have some considerations:

1.) If your system is oversized (> 100 % billing generation offset), you will probably always have an excess at some point(s) over 12 billing periods regardless of when trueup takes place.
In that case:
- If you get paid for the excess, choosing the billing period for trueup that has the greatest 12 month rolling net $$ excess may put the most $$ back in your pocket. The excess generation has a poor ROI, and that kills or greatly reduces system cost effectiveness, but if a system is in place and oversized, That train has left the station.
- If any excess generation for the prior 12 months is simply rolled over rather than (or NOT, that is with no option) paid for at wholesale rates, it won't matter much, but you might choose the billing period for trueup as the one with the least accumulated excess generation. Note however, and be careful: If the excess generation credit disappears after an additional 12 billing period carryover, congratulations - you own an oversized, less than optimally cost effective system. You options are then to burn off the excess generation by using it for tasks now done by other means, or leave the lights on, the A/C running or get an EV or something else you might not need to do or have planned on.

2.) If your system is sized for < 100 % offset, for most years, you''ll have a net bill due the POCO. In that case, when the trueup billing period is probably won't matter much.

[azdave]

Agree. If you don't have to decide right now and only get one opportunity then wait and learn more about your system and strategies before picking the date. I had no choice on my reset date but knew that going in and adjusted for it.

[loungelizard]

I would true up in October if I were you. Nice that you have a choice. I'm in Phoenix and have no option but to true-up annually on the last day of April. That is the end of the fiscal year for our utility.That is the worst possible time as we usually have over 4000kWh banked through the fall, winter and spring that we are not allowed to carry into summer. Instead, we get an account credit at wholesale rate and have to start over at zero balance, just before our heavy A/C season begins.

OK, thanks for that. Edison says we can only make one change so I want to make the right one. I know my monthly kWhs but I might wait 1 year just to get a feel for the NEM 2.0 and see how it works. Frankly, Edison doesn't do a very good explaining the change on their website.

[azdave]

I would true up in October if I were you. Nice that you have a choice. I'm in Phoenix and have no option but to true-up annually on the last day of April. That is the end of the fiscal year for our utility.That is the worst possible time as we usually have over 4000kWh banked through the fall, winter and spring that we are not allowed to carry into summer. Instead, we get an account credit at wholesale rate and have to start over at zero balance, just before our heavy A/C season begins.

[loungelizard]

I think you would want your PTO date as soon as possible to maximize your recovery. After that, what you may be referring to is the date for your annual billing cycle or True Up. I build reserve in the spring and summer and use it up in fall and winter. I can manage my loads and load shifting and therefore I prefer to have my True Up end when I have more options. For me that worked out to be spring.

Your mileage may vary. In my case I actually have a dollar credit at True Up but I am a net consumer in kWhs because of load shifting. For me the sweet spot is the smallest dollar credit and the largest net consumption. The credit washes out against the consumption in kWhs.

OK, thank you. That makes sense now. .

[Ampster]

I think you would want your PTO date as soon as possible to maximize your recovery. After that, what you may be referring to is the date for your annual billing cycle or True Up. I build reserve in the spring and summer and use it up in fall and winter. I can manage my loads and load shifting and therefore I prefer to have my True Up end when I have more options. For me that worked out to be spring.

Your mileage may vary. In my case I actually have a dollar credit at True Up but I am a net consumer in kWhs because of load shifting. For me the sweet spot is the smallest dollar credit and the largest net consumption. The credit washes out against the consumption in kWhs.