New system config in Bay Area

[activemind]

Wanted to run by my system config by you guys to make sure it looks okay:

Option #1 : 16 LG310, Enphase M250 4.96kW system at $3.62/kW ( this is 96% of current usage)

Option #2 : 18 LG310 Enphase M250 5.58kW system at $3.60/kW (this is 117% of current usage)

Option #3 : 18 LG320 Enphase S280 5.76kWh system at $3.65/kW (this is 121% of current usage)

After reading more here, I requested a quote for 18 LG315s with Enphase M280 - will update once I get that.

I have partial shading on my roof during some hours and hence I feel micro inverters are a better choice for me.

Also, I want to go more than my current usage because I foresee us using more energy when I charge my EV at home and add another AC unit to the house.

Comments?

-AM

[ButchDeal]

After reading more here, I requested a quote for 18 LG315s with Enphase M280 - will update once I get that.

I have partial shading on my roof during some hours and hence I feel micro inverters are a better choice for me.
-AM

I think you mean Enphase S280.

Have you considered SolarEdge. Would be cheaper and same benefits.

[activemind]

Sorry, yes S280. Still learning about all the acronyms and product names!

I was suggested by multiple installers (read 3) that because of the shading issue (I have a tall redwood that shades my roof for some hrs) I would be better off with micro inverters than string with power optimisers.

I am not married to any brand or technology but just want the most bang for my buck. Though I AM a little partial to LG panels.

-AM

[ButchDeal]

I was suggested by multiple installers (read 3) that because of the shading issue (I have a tall redwood that shades my roof for some hrs) I would be better off with micro inverters than string with power optimisers.

I am not married to any brand or technology but just want the most bang for my buck. Though I AM a little partial to LG panels.

-AM

Thats BS. SolarEdge isn't a string inverter with optimizers. It is an optimized system. The inverter will not work on it's own without the optimizers.
It has exactly the same effect as micros in handling shade.

I would suggest that your installers are married to the micros if they made this statement.

[activemind]

Thanks for your response Butch!

Looking at the panels, is LG 310 a good choice even if I switch to SolarEdge or do I need to revisit those too?

And my decision to go with 117% of my current usage?

-AM

[ButchDeal]

Thanks for your response Butch!

Looking at the panels, is LG 310 a good choice even if I switch to SolarEdge or do I need to revisit those too?

And my decision to go with 117% of my current usage?

the LG310 will work with SolarEdge perfectly fine, as will almost any other LG Module

Some utilities in CA limit you to 110% and a few to 100% so that should be checked. If you recently purchased an EV then you could easily get an exception.

If you have any tiered pricing then 117% would be less cost effective than say 80%

[thejq]

Another factor to consider is the financial stability (or bankability). ENPH is not in great shape right now. SEDG has taken a beating, but still profitable with reasonable capitalization. Some installers like Enphase, because it's easier to install, less work = more profit. In CA, with the minimum usage charge of $10/month, your consumption calculation needs to start with $120 lower than your full usage. Normally with your size, you need to shoot for 85%-90% of your current usage in order not to leave money on the table at true-up time. Anything more, you will be wasting your money unless you expect your usage to increase in the future.

[activemind]

I currently own a EV and charge at work (not free) which I plan to start charging at home once solar is installed. I am also planning on getting AC on second floor. So yes, I am expecting my usage to go up anyways.

How did you arrive at the 85%-90% usage number? Could you point me to any spreadsheet or calculator that would give me a ballpark idea of the size (from a financial perspective) compared to usage ?

Looking at my usage last month (without EV and AC):
Tier 1 - 313kWh - $56.99@18.2c/kWh
Tier 2 - 94kWh - $30.5@22.4c/kWh
Tier 3 - 212kWh - $60.52@28.6c/kWh

Thats 619kWh. 619*12 = 7428kWh ( I know thats a VERY linear approximation).

Hence trying to go to a 5.5-5.7kWh system (18 LG310s).

[thejq]

I currently own a EV and charge at work (not free) which I plan to start charging at home once solar is installed. I am also planning on getting AC on second floor. So yes, I am expecting my usage to go up anyways.

How did you arrive at the 85%-90% usage number? Could you point me to any spreadsheet or calculator that would give me a ballpark idea of the size (from a financial perspective) compared to usage ?

Looking at my usage last month (without EV and AC):
Tier 1 - 313kWh - $56.99@18.2c/kWh
Tier 2 - 94kWh - $30.5@22.4c/kWh
Tier 3 - 212kWh - $60.52@28.6c/kWh

Thats 619kWh. 619*12 = 7428kWh ( I know thats a VERY linear approximation).

Hence trying to go to a 5.5-5.7kWh system (18 LG310s).

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.

[activemind]

Excellent analysis. Thanks for running this for me.

The 5.76kWh is projected 7871kWh/yr which lines up pretty nicely. I live in Bay Area, CA so PGE territory.

We (as a family) are working towards pushing things to off peak but some things are just non negotiable (got 2 young kids).

I would love to be able to charge my EV at home off of solar but its not a do or die. I can get by charging at work!

Any opinion on LG320s with S280 ? Its coming out to be $3.65/Watt. 25 years is a loooong period to be able to predict all the variables!

[TLUGO]

Hey activemind have you considered Freedom Solar?

[activemind]

Just to add to calculations... i looked at my EV usage. I typically use 270 kWh every month. So i think i am sizing the system correctly by going to 120% if i want to charge my car at home.

No, i haven't looked at freedom solar. I will look at them on yelp but i am already deep in talks with 3 other places at rates posted above.

[quitepossibly]

How is the condition of your roof? The last thing you want to happen is to have a leak underneath your solar array.

[activemind]

Roof is in pristine condition. Cement flat tile roof. 3 solar guys who went up there gave the same feedback about roof condition.

[J.P.M.]

OP: On tiered rates (coming to an end soon to a utility near you), the first several thousand kWh/yr. you used were at the lowest tier. Bottom line: Systems that offset an entire load were offsetting more lower cost (tier1) electricity with expensive solar. That hurts system cost effectiveness.

Check out something called L.O.C.E. (levelized cost of electricity). That's one tool to estimate the most cost effective system size. Basically, there are several ways to use LOCE depending on the goals set by the owner.

One way it works for PV systems is: If the LOCE of the PV supplied power is less than the LOCE of the POwer Company electricity it replaces, the system size is cost effective by the parameters chosen.

As a practical matter, with current tiered rate tariffs, the most cost effective PV system per kWh produced is usually the one that only replaces the tier 3 stuff, or maybe a bit more depending on system price/Watt reductions for larger system sizes. The most cost effective systems are thus not 100% offsets, but do replace the most expensive electricity. This is somewhat reinforced by the idea that larger systems often cost less per nameplate Watt.

Another way to use LOCE is to run the system size up until the LOCE for the PV supplied power equals the LOCE of the stuff it replaces. Since the most cost effective systems, by some definitions, offset the most expensive electricity (the tier 3 stuff.), this method does not necessarily produce a more cost effective system per nameplate Watt than one that stops at tier 3, because it dips down into the lower tiers, replacing less expensive electricity with what is probably more expensive PV electricity, thus lowering the LOCE of the replaced power.

All this is predicated on the hope that the LOCE of the PV power is less than the cost of tier 3 power. If it isn't then PV will not be cost effective under the LOCE parameters chosen and used. The option then is to either change the LOCE parameters, or don't get PV and expect it to be cost effective.

For T.O.U. rates, which we'll all be on some day, things stay pretty much the same for the LOCE of the PV supplied power, but get a bit more complicated when trying to find a realistic estimate for the LOCE of T.O.U. POCO power (sorry for the alphabet soup). Without having been on T.O.U., It is necessary and possible to estimate how much power is used and the TIME of that usage and thus the cost of the power you use, or perhaps have the POCO supply that info. Then after transferring that cost to a LOCE # is pretty much the same method as for the tiered rate power. Studying T.O.U. time schedules and adjusting some use patterns (time shifting) can also be cost effective, and change the LOCE of the POCO power (downward), and thus perhaps affect PV system size and relative cost effectiveness, but may not be worth the hassle of the lifestyle adjustment(s).

A tip: think about lifestyle adjustments and conservation measures BEFORE adding PV - not after. Do the cheap stuff first. PV is the most expensive way to offset an electric bill.

Once the concept of LOCE is understood, the method can be a valuable tool for system sizing and optimization. It isn't the only tool, and like all such tools it is sensitive to the assumptions made about the future and can be misused or misapplied in ways that may not bear much resemblance to reality or likely expected conditions. For example, using a time frame of 25 years can make most any system cost effective, even one that might cost $6.00/Watt and offset 120 % of any expected load. If you plan on moving in 7 or 8 years, 25 years may not be an appropriate number to use. Some honest assessments about things are necessary. This is not the place for wishes or rose colored glasses.

One can always ignore the results. However, the method does allow a way to estimate and perhaps see the relative cost penalties associated with a 100 % offset system. Such penalties may not be that bad, or may not exist, or they may be vey costly. Having more information before making a decision involving several 10's of thousands of dollars that will also likely affect a family's lifestyle for the next 10-12 years for the cost of a little time spent on some information gathering and some number crunching doesn't sound like a terrible idea to me.

Take what you want of the above. Scrap the rest.