West Facing & Oversize or Battery Storage - What's Better For Time Of Use Rate Plan?

[nifty-stuff.com]

I'm in California on a Time Of Use rate plan (grandfathered into E-6) where electricity is much more expensive during peak usage times from 4pm - 9pm (when solar isn't producing as much... i.e., the duck curve of solar & consumption).

I already have a 3kw system facing south, but it is no longer enough to cover our usage. I'm kicking myself for not sizing it larger 10 years ago when I got solar installed.

I'm debating what will produce the overall long-term bang for my buck. There are a handful of options / configurations. A few things I'm considering:

• Over-build my system and send excess power back to PG&E at a lower rate
• Have my panels facing West. Even though less efficient, they will produce more power during the evening than the South facing
• Battery backup to grab excess during the peak times and use it in the evening

I haven't run the numbers yet, but my gut is saying it might be best to add a new system facing West and oversize it considerably. It seems that this would be cheaper and easier than a big battery backup system, and would break-even much sooner. (basically, swapping out the price of a large battery backup in exchange for a bunch of extra panels facing West).

What do you think?

... basically the idea is similar to what they found in research here:

Overbuilding solar cheaper than seasonal storage and natural gas in Minnesota

An analysis by Clean Power Research, commissioned by the MN Solar Pathways Initiative, shows that 10% solar by 2025, and 70% wind+solar+storage in 2050 can be achieved at a comparable cost to natural gas-fired generation.

pv-magazine-usa.com

 

[jasonhc73]

• double axis tracker wins every time in every situation for most energy collected (but is the most expensive also, and the tradeoff for just more panels wins)
• single-axis tracker (time of day tracker) is about 44% more energy than a fixed angle panel.
  • Some single-axis systems can more than double the solar energy collected.
  • A seasonally angled setup that also follows the daily sun.
• west angled panels will very much help with evening TOU rates, without the use of a somewhat complex and mildly expensive tracker.
  • Adding west-facing panels will allow the same inverter you have to be used, and not risk you clipping production
• south facing will collect the most energy throughout the entire day.
  • If you can adjust the angle at least 3 times a year, you will significantly improve collection. 14° in June vs 62° in December ~ not so significant change in the solar energy collection as a daily single-axis tracker, but somewhere in the ~5%-10% on an annual basis difference.
• Adding battery backup to any of the three setups will store and then immediately offset the TOU as long as you can control or have the backup switch over becoming automatic to use the times of the TOU.

In the long run, you will never gain anything from sending your E- back to the grid. Even when they buy them from you, are they crediting your account or actually giving you payment? Since 2017 every grid provider in the country is wising up to the threat that solar has become. It is very extreme in California, for example, the "Duck Curve". The tesla power explicitly combats that duck, however, it is extremely expensive, and the wait to have it installed is comical.

10 years ago, your panels cost far more and had far less potential than now.
Just two years ago for me, a 4kW system cost 20% more than the 6kW system I put up. In just two years, I installed 1.5 times for 20% less cost!

 

[FilterGuy]

I'm in California on a Time Of Use rate plan (grandfathered into E-6) where electricity is much more expensive during peak usage times from 4pm - 9pm (when solar isn't producing as much... i.e., the duck curve of solar & consumption).

I already have a 3kw system facing south, but it is no longer enough to cover our usage. I'm kicking myself for not sizing it larger 10 years ago when I got solar installed.

I'm debating what will produce the overall long-term bang for my buck. There are a handful of options / configurations. A few things I'm considering:

• Over-build my system and send excess power back to PG&E at a lower rate
• Have my panels facing West. Even though less efficient, they will produce more power during the evening than the South facing
• Battery backup to grab excess during the peak times and use it in the evening

I haven't run the numbers yet, but my gut is saying it might be best to add a new system facing West and oversize it considerably. It seems that this would be cheaper and easier than a big battery backup system, and would break-even much sooner. (basically, swapping out the price of a large battery backup in exchange for a bunch of extra panels facing West).

What do you think?

... basically the idea is similar to what they found in research here:

Overbuilding solar cheaper than seasonal storage and natural gas in Minnesota

An analysis by Clean Power Research, commissioned by the MN Solar Pathways Initiative, shows that 10% solar by 2025, and 70% wind+solar+storage in 2050 can be achieved at a comparable cost to natural gas-fired generation.

pv-magazine-usa.com

Are you sure about your E6 plan?

I am on the E6 plan with PG&E and that means I sell solar power at a high price when the sun is shining and buy power at night at a low rate. (At least thats what I thought) That means batteries do not make sense for me....except for power-fail. So far, I have avoided the planned safety blackouts.... so I have not installed battery at home. Right now my solar output is enough that the only thing I pay PGE is the minimum ~$10/month. If they did not have the minimum, I would be paying nothing. In 2022 I will loose the E6 grandfathering and will probably install batteries then.

Will you be able to keep E6 when you make the changes?

 

[nifty-stuff.com]

Thanks for the replies guys! Sorry I didn't get notifications of them sooner!

If you can adjust the angle at least 3 times a year, you will significantly improve collection. 14° in June vs 62° in December ~ not so significant change in the solar energy collection as a daily single-axis tracker, but somewhere in the ~5%-10% on an annual basis difference.

Wow, that's a REALLY interesting idea! I always just assumed tracking / adjustments would be all-or-nothing. Hadn't even considered a 3x a year approach!

In the long run, you will never gain anything from sending your E- back to the grid.

Yup, VERY true! I just read that after the annual true-up that PG&E will only buyback power at like $0.02 - $0.04 / kwh!

Are you sure about your E6 plan?

I am on the E6 plan with PG&E and that means I sell solar power at a high price when the sun is shining and buy power at night at a low rate. (At least thats what I thought)

Umm... I *think* so? ... what you're saying (sell high, buy low) sounds right.

Will you be able to keep E6 when you make the changes?

I'm pretty sure I will be able to, but I'd definitely double-check that first.

 

[Steve_S]

First things first… don't be upset you did not "upsize" 10 years ago, it would have cost you 70% more at that time and today you would have much less generating capacity overall because none of the equipment is at todays spec's & standards. IN fact many are yanking old panels & upgrading them... My neighbour is doing that this spring, replacing the 150W panels on his roof with 340W panels (which are costing him 1/2 of what the 150's did way back when) and he can sell the good ones off at 50-75 a piece. (New Q panels only costing 240 ea)

So before going off on a tangent, you may want to consider if it may actually be worth upgrading the existing array & gear for more performance, it may actually not be as bad as you think, all the underlying basics are already there. Next a respectable tracker with a nice array can make a LOT of juice as well and could certainly supplement your current fixed array. Trackers are not cheap BUT that get's made up for the amount of power generation they provide, so it balances out over time and actually increases your ROI.

I personally am no fan of Grid Power Beasts (ok, I am offgrid and loving no power co hostage fees). I would suggest a good battery system @ 48V which can be expanded as needed / wanted in stages. You can initially start off smaller and add-on as you go, taking the initial "sting" out of it while still providing you basics... IN the interim, you could setup so that the grid become "your backup" to recharge your batteries at night (low peak times) if the solar system can't fully charge them or if your using more than your stored capacity. Keep in mind if you are not selling / buying power you aren't paying taxes per kwh & no fees for it... only for what you are using right.... (self generation, storage & use is tax & fee free)

Overbuild & Over-panelling is a tricky area and not something to be considered lightly !!! This takes serious number crunching and planning, it's quite easy to overrun a system and burn it up... happens a lot but no one ever mentions how they screwed up because they are too embarrassed or some other equally stupid reason (90% ego related). Yes you can do so with a safe margin of 10-15% as no panel will ever see 100% capacity reached ad provided you have equipment that can handle a bit over the specs for input. Midnite Classic solar controllers are one such example.

I should also point out that companies like Santan Solar in Arizona sell new & used panels at serious discount https://www.santansolar.com/product/ and if you are not hung up "it has to be perfect, NEW & Shiny" then look at their NEW products... then go online and compare with places like Alt-E and others...

Lastly, you did not mention what kind of gear you have at present. Depending on brands, model etc you may be able to expand or update / enhance the current equipment as well... If you have a product line & brand that is still a "current family member" of products being produced that would be a bonus, hopefully it is expandable gear which again could save a large amount of cash. As well, there may be newer updated products that would increase your generation potential... for example if you have PWM solar controllers, replacing them with MPPT will give you an immediate increase without changing anything else. A LOT has changed in 10 years !

Hope that helps.
Steve

 

[nifty-stuff.com]

Wow Steve! So much great info there!!! Thanks!!!

First things first… don't be upset you did not "upsize" 10 years ago, it would have cost you 70% more at that time and today you would have much less generating capacity overall because none of the equipment is at todays spec's & standards.

Really good point! As I'm looking at prices, I can already see that Tesla solar is about 1/3 of what I paid per watt 10 years ago!

Trackers are not cheap BUT that get's made up for the amount of power generation they provide, so it balances out over time and actually increases your ROI.

The more I think about it, I like the idea of a system that's pretty passive. I worry too much about moving parts breaking over time.

I would suggest a good battery system @ 48V which can be expanded as needed / wanted in stages.

I used to think I wouldn't ever need / want battery backup, but with all the shutoffs happening in CA, I'm considering them more and more.

Overbuild & Over-panelling is a tricky area and not something to be considered lightly !!! This takes serious number crunching and planning, it's quite easy to overrun a system and burn it up

Hmm... I'll definitely need to put more thought into that!

I should also point out that companies like Santan Solar in Arizona sell new & used panels at serious discount

EXACTLY! I've been checking them out a LOT and it's sooooo tempting to give them a try... especially with the crazy sale they have coming up for Valentines day!

Lastly, you did not mention what kind of gear you have at present. Depending on brands, model etc you may be able to expand or update / enhance the current equipment as well

I think I'm going to be stuck with keeping the existing system separate from the new. My system:

1. 3.9 kw (DC)
2. 18 - REC Solar 220 watt panels
3. 18 - Tigo energy optimizers
4. SMA-Sunny Boy 4000US inverter
5. Net System Cost after all incentives, etc. $13,901.60

It's all working just fine, and well enough to leave / not tear-out, but also so old/unique setup that I can't add to/expand it directly.