Simple AC-coupled solar production monitor /meter to control dump load / relay

[GregTR]

This article was just posted and seems quite apropos in our NEM discussion; https://pv-magazine-usa.com/2022/09/27/why-did-i-reform-my-views-on-net-energy-metering-nem/

 

[fafrd]

This article was just posted and seems quite apropos in our NEM discussion; https://pv-magazine-usa.com/2022/09/27/why-did-i-reform-my-views-on-net-energy-metering-nem/

As soon as he said this:

‘I also believe that export compensation should be lowered from retail rates but not suddenly and certainly not retroactively.’

I knew he and I would be on the same page. It’s the changing terms on solar customers who have already made the investment in solar that has me most worked up.

The one thing missing in his argument is the higher cost of rooftop solar versus solar farm-scale solar. Solar farms have other social costs including unsightliness and rooftop solar has other benefits including jobs, so making a decision between the two is not one-dimensional but the difference in cost/efficiency needs to be considered.

My bottom line is that if a consumer has the resources to generate and consume their own solar energy without impacting the grid, they should be free to do that (and even encouraged / incentivized).

Charging a customer with solar who never exports to grad a solar tax or a higher electrical rates than a standard electrical customer should not be allowed.

A minimum monthly bill achieves that - if it gets too high, solid customers can go true off grid and rely on generators for backup instead of the grid. But at least a minimum monthly charge treats solar and non-solar customers equally.

 

[GregTR]

I think the issue here is that there are two costs associated with the grid just like with anything else in economics: fixed cost and marginal cost.

Even if I only choose to supply you with 1kWh or electricity there is certain cost in maintaining the transformers, the meters, the line to your house, the billing department etc. This is what the monthly charge is meant to cover. Now charging more just because you have solar means that the billing is not true and not genuine and some of this fixed cost is rolled into the marginal cost of the utility which solar customers are not paying fairly.

The problem they're trying to solve is by rolling some of the fixed cost into the marginal cost is that you're essentially making a scenario where price discrimination exists; the richer you are and the more electricity you use, the more of the fixed cost burden you're straddled with. The problem is that this model falls apart with solar in the picture as you will have richer users who are now no longer paying "their fair share" compared to the poorer folks for the fixed cost aspect of the power delivery or the subsidy of the power delivery.

The solar fee is trying to "fix" this by putting some of the cost back on the solar folks. The problem is that it's a really tough pill to swallow but I think the situation reflects the truth or some shape of it.

Oh, today I got my battery installed, I had a great time with the installers, they did a really nice job with running conduit from the Sol-Ark to the Homegrid Stack'd system and using 4/0 wire between the two.

My Sol-Ark is fully closed loop communicating with the Homegrid Stack'd system and receives perfect and accurate SOC readings via CAN-BUS and I can still use Solar Assistant using Modbus on the same port with a splitter. The entire system "just works".

There is no doubt in my mind that this setup is the one to get if one can afford it. The Sol-Ark 15K is an amazing piece of equipment and the Homegrid Stack'd is a really nice package! I decided to max mine out so next week they will bring another module so I'll have 38.4 kWh in one nice stack that will just work amazingly well.

The units arrived with 50% SOC and I burned them down to 25% SOC and now, since it'sjust after 9PM I'm charging them from the gird for free. I'm about to load 20+ kWh into these bad boys absolutely free!

My PTO also came through tonight so I am going to finally start selling to the grid during the day and reaping some of the limited benefits of grid sell, but more importantly I will finally have an opportunity to really exercise my system and see what it's capable of!

 

[fafrd]

I think the issue here is that there are two costs associated with the grid just like with anything else in economics: fixed cost and marginal cost.

Even if I only choose to supply you with 1kWh or electricity there is certain cost in maintaining the transformers, the meters, the line to your house, the billing department etc. This is what the monthly charge is meant to cover. Now charging more just because you have solar means that the billing is not true and not genuine and some of this fixed cost is rolled into the marginal cost of the utility which solar customers are not paying fairly.

The problem they're trying to solve is by rolling some of the fixed cost into the marginal cost is that you're essentially making a scenario where price discrimination exists; the richer you are and the more electricity you use, the more of the fixed cost burden you're straddled with. The problem is that this model falls apart with solar in the picture as you will have richer users who are now no longer paying "their fair share" compared to the poorer folks for the fixed cost aspect of the power delivery or the subsidy of the power delivery.

The solar fee is trying to "fix" this by putting some of the cost back on the solar folks. The problem is that it's a really tough pill to swallow but I think the situation reflects the truth or some shape of it.

Oh, today I got my battery installed, I had a great time with the installers, they did a really nice job with running conduit from the Sol-Ark to the Homegrid Stack'd system and using 4/0 wire between the two.

My Sol-Ark is fully closed loop communicating with the Homegrid Stack'd system and receives perfect and accurate SOC readings via CAN-BUS and I can still use Solar Assistant using Modbus on the same port with a splitter. The entire system "just works".

There is no doubt in my mind that this setup is the one to get if one can afford it. The Sol-Ark 15K is an amazing piece of equipment and the Homegrid Stack'd is a really nice package! I decided to max mine out so next week they will bring another module so I'll have 38.4 kWh in one nice stack that will just work amazingly well.

The units arrived with 50% SOC and I burned them down to 25% SOC and now, since it'sjust after 9PM I'm charging them from the gird for free. I'm about to load 20+ kWh into these bad boys absolutely free!

My PTO also came through tonight so I am going to finally start selling to the grid during the day and reaping some of the limited benefits of grid sell, but more importantly I will finally have an opportunity to really exercise my system and see what it's capable of!

Sounds like a really nice rig!

What did you pay per kWh for your batteries?

The Solark represents the Mercedes Benz of current Hybtids, from my perspective.

I’d love to put in a Solark-based rig but it just wouldn’t make economic sense for me.

My 2016-era electrical bill was $700/year, so spending $5000 on a 4kW Microinverter-based grid-tied array made sense and with tax credits, I’ve probably broken even by now (6 years later).

But I’m only going to be facing new charges when they force the solar tax on me, currently planned for 9 years from now.

Until then, the worst thing I might need to deal with is monthly billing (which means adding more solar panels to cover more of daily consumption; a better hybrid really won’t be much help.

At wholesale rates of $0.05/kWh, it’s hard to justify extra solar panels, but once you start talking $0.20-0.30 per kWh, even only over the winter months, it starts making sense very quickly…

Beyond more panels, I’ll eventually need more battery capacity if they ever change the rates to the point that a kWh exported during the month won’t cover the cost of a kW consumed late at night, but that’s where I’m hoping the EV will come in.

And with Emporias bidirectional charger + Energy Monitor priced at under $1600, that seems like a much more realistic budget to spend on overnight offset than the price of a Solark.

Backup power is absolutely not a priority for me - it’s just about generating enough electrical power to offset electricity biils (as long as that makes economic sense).

On the question of NEM agreements, I’m totally with you as far as new customers. The customers who have already hooked-up should not have the terms changed on them after the fact (bait and switch).

And if only wealthier customers can afford to take themselves completely off of the grid, they should have the freedom to do that. It results in more grid capacity and a healthier grid for everyone else.

And I’m even OK with a huge rehookup fee if you try to go off-grid and decide it was a mistake.

Aside from not changing the rules after the fact, my main thing is to apply the same rules to everyone. Call the solar tax an ‘export right fee’ or an ‘export fine’ on months your are caught exporting, and I’m 100% on board.

You grew carrots (generated energy) and ate them (consumed it) so you will pay us a tax on the market value of your carrots (an solar tax even if you exported no energy the the grid and are disconnected from it), I am not.

 

[GregTR]

Yeah, I do realize that the Sol-Ark 15K is probably the top dog on the market today, but when you look at large scale residential PV, it actually starts making sense, even from a cost perspective.

All in, after the 30% federal tax credit I'll end up paying $2.56/W for my system, including the 38.4 kWh battery backup. That is a really competitive price. If I take out the cost of the battery I'm paying a mere $1.61/W after the federal credit.

Solar only cost:
$2.30/W cash, $1.61/W after federal credit. This is incredibly competitive in today's market. I got a Sol-Ark 15K, Tigo Optimizers, Aptos 440W panels, Unirack racking and mount system, grid disconnect switch and all conduit and wiring.

Battery cost:
$685/kWh cash, $480/kWh after federal credit. This is not as cheap as I could have gotten had I gone with Lifepower from signature solar which is now UL listed and would have worked fine, but this did include a day's work of two guys, conduit for the 4/0 wire, and about 30 ft of 4/0 wire.

With the solar, estimating a 20 year lifetime and 1.29 kWh/W/year I'm estimating 25.8 kWh/W generation which means about $0.105/kWh for electricity including the batteries and assuming 94% self consumption (these are the modeled numbers I got based on my usage data and optimal battery strategy). This hinges on no net metering, no grid export of any kind, just limit to load consumption and using the battery for solar storage.

Now if I can stay on my current power plan with free nights my math gets even better as I can easily assume that I will cover all my power needs and I can safely estimate about 35,000 kWh/year benefit from the panels. At that rate I'm looking at net cost of $0.044/kWh which is an absolute steal! This is again, no grid export and including the cost of batteries.

So yeah, $50k out of pocket for a system is definitely a lot of money up front and not for everyone. But if I assume that solar adds 3-4% to the value of a home I made a solid investment and I will get the money back almost immediately just by virtue of increased home value.

 

[fafrd]

Yeah, I do realize that the Sol-Ark 15K is probably the top dog on the market today, but when you look at large scale residential PV, it actually starts making sense, even from a cost perspective.

All in, after the 30% federal tax credit I'll end up paying $2.56/W for my system, including the 38.4 kWh battery backup. That is a really competitive price. If I take out the cost of the battery I'm paying a mere $1.61/W after the federal credit.

Solar only cost:
$2.30/W cash, $1.61/W after federal credit. This is incredibly competitive in today's market. I got a Sol-Ark 15K, Tigo Optimizers, Aptos 440W panels, Unirack racking and mount system, grid disconnect switch and all conduit and wiring.

Battery cost:
$685/kWh cash, $480/kWh after federal credit. This is not as cheap as I could have gotten had I gone with Lifepower from signature solar which is now UL listed and would have worked fine, but this did include a day's work of two guys, conduit for the 4/0 wire, and about 30 ft of 4/0 wire.

With the solar, estimating a 20 year lifetime and 1.29 kWh/W/year I'm estimating 25.8 kWh/W generation which means about $0.105/kWh for electricity including the batteries and assuming 94% self consumption (these are the modeled numbers I got based on my usage data and optimal battery strategy). This hinges on no net metering, no grid export of any kind, just limit to load consumption and using the battery for solar storage.

Now if I can stay on my current power plan with free nights my math gets even better as I can easily assume that I will cover all my power needs and I can safely estimate about 35,000 kWh/year benefit from the panels. At that rate I'm looking at net cost of $0.044/kWh which is an absolute steal! This is again, no grid export and including the cost of batteries.

So yeah, $50k out of pocket for a system is definitely a lot of money up front and not for everyone. But if I assume that solar adds 3-4% to the value of a home I made a solid investment and I will get the money back almost immediately just by virtue of increased home value.

$0.105 per kWh or $0.044 per kWh are both excellent electricity rates by California standards. We may $0.30/kWh off peak and $0.50/kWh over summer months (and $0.20/0.25 over the winter).

But install is a big part of the cost and scales better with larger systems. I’m guessing you consume a great deal more than the ~4.5MWh/year that I consume.

My system was circa 2016 and because I installed it myself, the entire 4kW grid-tied system with panels and Microinverters cost me $1.25/kW ($5000) or under $1/kW with tax breaks at that time.

Now that I’ve basically paid for that array, hopefully I’ll be able to find ways to adapt to the changing rules without it costing me an arm and a leg.

Your battery a $685/kWh was a bit pricey, but including install probably worth it.

When I wanted a battery 18 months ago, there were no affordable OTS options.

I built my $14.5kWh battery for only $104/kWh based on rated capacity but I suspect actual capacity falls short of that. Currently, the most I’m using in the peak of summer is 8kWh so it cycles at least 55% of it’s rated capacity with ease.

Hopefully my future EV will give me total storage capacity 2-3 times what you’ve got at an overall cost/kWh that is not much higher per kWh…

And hopefully by that time there will be a bidirectional-charger-based hybrid solution that allows to store all of my daily generation for overnight consumption offset for a fraction of what a Solark costs…

 

[GregTR]

Yeah, I used 4.2MWh in July alone so my consumption is a "bit" more than yours.

My pre-solar-purchase electricity rate was $0.089/kWh all day every day. This is what made solar ROI not really viable in Texas in the past and the only people who bought it were the ones who wanted to virtue signal or got duped by sales people. Historically, solar has been getting cheaper year over year which made the proposition of buying now vs. later even less appealing.

The cheapest rates currently available are $0.13 for a 36 month lock-in period so even at that rate solar makes sense. Combine that with the inflation and price uncertainty of solar and I think the time was now to jump in.

The non-tangible benefit for me is the addition of resiliency. I WFH now so having reliable power is a bit more important now than it ever was.

 

[fafrd]

Yeah, I used 4.2MWh in July alone so my consumption is a "bit" more than yours.

My pre-solar-purchase electricity rate was $0.089/kWh all day every day. This is what made solar ROI not really viable in Texas in the past and the only people who bought it were the ones who wanted to virtue signal or got duped by sales people. Historically, solar has been getting cheaper year over year which made the proposition of buying now vs. later even less appealing.

The cheapest rates currently available are $0.13 for a 36 month lock-in period so even at that rate solar makes sense. Combine that with the inflation and price uncertainty of solar and I think the time was now to jump in.

The non-tangible benefit for me is the addition of resiliency. I WFH now so having reliable power is a bit more important now than it ever was.

With consumption like that, your rig would practically qualify as a small Solar Farm here on n the Bay Area!

Between the lowest in the land electricity rates in Texas slowly creeping up, the severe grid issue of a few years ago, and the continued trend towards lower and lower cost for solar technology, it finally makes economic sense to add solar in Texas - that’s a major milestone!

I would love to have a high-end system like yours but with my much more modest consumption levels, it just wouldn’t make economic sense (tax breaks or no).

And at your consumption levels, I agree - use of an EV as extended battery wouldn’t make sense - that’s slot of power you’d wast anytime the EV wasn’t present and you’d be cycling the EV close to 200 miles equivalent per day.

For me, the ‘gap’ I’ve got to close between my existing 8-10kWh battery and offsetting load all way through until after the breakfast surge when solar reaches the level to once again take over translates to only 10-20 miles of driving daily (and if the EV is not there to capture a days excess production, it’s not that big of a deal in terms of lost energy).

So the architecture I see eventually becoming commonplace here in California probably won’t make sense in high-consumption areas like Texas…

 

[daklein]

Maybe an old thread, but good discussion. How did those CT clamp power switches work out? Could be useful for some cases.

You mentioned Emporia, hoping to get them to offer a configurable excess solar or power measurement switch, not so likely I think... If you have any home automation inclination, there is a python library, PyEmVue which allows one to read the data from Emporia Vue, and control Emporia EVSE. It still works through Emporia's cloud, but, it works. There is integration with Home Assistant for it also. Further down the hacking line is ESPhome which can replace the firmware on the Emporia Vue, so you can read the power data locally without using the cloud at all.

 

[GregTR]

I have Home Assistant and I am using the Emporia integration with it. Since I currently have free nights and also a battery, I have yet to invest too much time into getting things automated to maximize solar use, I'm better off just exporting all the excess and charge my EV at night.

But if the time comes where free nights go away I'll be sure to look more into it.