"Net metering" cancelled - alternatives

[theoldwizard1]

So in the midst of one of the cold snaps in recent memory here in SE MI I am think about solar power. A few years ago, the MI Public Service commission changed from "net metering" (hopefully the correct term) where the PoCo (DTE) would "buy back" any excess power from you, AT RETAIL RATES, until you had reached a "zero" bill. Now, they only buy back at commercial rates, making your cost recovery much, MUCH longer ! Plus, they have added a large number of other "steps" to getting hooked up, some at your expense, before you can "sell" any power back to the grid.

Gone are the days of just plugging a micro-inverter directly into an outdoor 120V receptacle ! I think I have come up with a still cost effective solution, but I am sure others have done similar. I believe this type of system is called a "hybrid system".

Solar panels charge a battery bank. The battery bank feeds an inverter with an split phase 240VAC output. Output feeds the "load". With the crappy amount of sun we get here in SE MI, especially during the winter, it would be very difficult (cost and size) to have a solar array and battery bank large enough to cover all loads. What is required is a transfer switch to switch the load from battery/inverter to PoCo line power when the battery bank is "low". At the same time, the line could optionally charge the battery bank. The PoCo also got permission to can their rates for a more expensive "peak" usage, so maybe charge the battery bank off peak ? Conceptually, this is the same as a mobile "all-in-1" inverter/charger/transfer switch.

Has anyone built a system like this and how well does it work ?

 

[Brett V]

What you describe is just about any commercially available AIO. Growatt, EG4, Victron is a bit more modular but still the same idea.

 

[Mattb4]

No shortage of Off grid AIO's that allow you to have grid as backup. Some call themselves "Hybrid" though the term is a bit fluid at the moment and many prefer to only use hybrid to describe grid tie AIO's that allow grid feed but do not necessarily grid feed.

Typical off grid AIO's incorporate a UPS type function with PV charging. So they have a SCC (most likely MPPT), ATS (Automatic transfer switch), Inverter/charger, and a CPU to control function. Feature sets of some allow time of day settings for grid charge.

 

[Hedges]

Instead of off-grid system with transfer switch, consider a zero-export grid-tie system. Or if not too many hoops to jump through, a grid-tie "net meter" system, so long as the backfeed credit is not less than zero.

Then control loads to utilize power when you produce it, to the extent practical.

There are AC coupled batteries (e.g. Power Wall) that can be configured to charge with your GT PV surplus as a way to avoid exporting or curtailing.

But you do have to consider whether there are monthly fees or different rate schedule when using net metering.

I haven't built that because I still have net metering. I just try to run large loads when rates are low. I haven't bothered with using batteries for time shift of export because I make enough PV for credits earned when the sun shines. Looks like I got careless this year, burned through the credits as of 3 weeks ago and true-up is in another 5 weeks. I've switched heating back to gas furnace, don't know if my production will supply consumption during this period or not.

 

[theoldwizard1]

Instead of off-grid system with transfer switch, consider a zero-export grid-tie system. Or if not too many hoops to jump through, a grid-tie "net meter" system, so long as the backfeed credit is not less than zero.

If the sun is providing power, I want to store it somewhere. If they won't let me (cost effectively) use the grid as a "battery" I'll just have to buy my own !

 

[theoldwizard1]

What you describe is just about any commercially available AIO. Growatt, EG4, Victron is a bit more modular but still the same idea.

I have not seen one that, when battery power is low (so you are "on grid"), allows solar charging but no grid charging during certain times of day.

Does this exist ?

 

[hwy17]

Has anyone built a system like this and how well does it work ?

Yes most of us on this forum I would say are building systems like this.

There are so many different ways to do it and there are people trying all of them.

 

[hwy17]

I have not seen one that, when battery power is low (so you are "on grid"), allows solar charging but no grid charging during certain times of day.

Does this exist ?

It does. Schneider, EG4, Solark, Outback.

Essentially all of the hybrid solutions will contain some kind of TOU based logic.

The question is, how good is it. How much sense do the settings make, do they do what you want them to, do they do everything you want them to, etc.

And that's an ongoing discussion, you can find many threads of people pulling their hair out when the settings aren't doing what they're trying to do.

 

[Hedges]

I think LiFePO4 batteries like server rack and PowerPro get down to $0.05 or $0.10 per kWh of cycle life, based on their specs.

GT PV hardware I put at $0.025 (amortized over 20 years), and turn-key installed GT PV systems $0.10/kWh.

With batteries, have to determine cost of system including inverter and transfer switch. Some of the hybrids support battery and sell for a price similar to tier-1 GT PV inverters, so overall could compete with all but the lowest utility rates.

One challenge is system must support starting surge of loads. Typically surge is 5x running load, so a 2 HP motor rated for 3500 VA might pull 17 kVA from inverter. That is where GT PV, with optional AC coupled battery, makes it easier. Use the grid for surge, otherwise supply from PV and battery.

If your system can't keep up with daily kWh demand, grid tie would allow grid to pick up the rest. An off-grid system could switch onto grid and also start charging battery from it. With something like Chargeverter, grid could supply just the additional (DC battery voltage) current needed to keep running loads.

Are you looking for whole-house backup when grid is down? If not, GT PV zero-export with AC coupled battery may be the way to go.

A hybrid like SolArk with CT at utility meter could do that plus provide battery backup to smaller selected loads. Leave larger loads like electric furnace direct on grid, but SolArk would backfeed house to supply it, to the extent battery and PV supports.

 

[Adam De Lay]

So in the midst of one of the cold snaps in recent memory here in SE MI I am think about solar power. A few years ago, the MI Public Service commission changed from "net metering" (hopefully the correct term) where the PoCo (DTE) would "buy back" any excess power from you, AT RETAIL RATES, until you had reached a "zero" bill. Now, they only buy back at commercial rates, making your cost recovery much, MUCH longer ! Plus, they have added a large number of other "steps" to getting hooked up, some at your expense, before you can "sell" any power back to the grid.

Gone are the days of just plugging a micro-inverter directly into an outdoor 120V receptacle ! I think I have come up with a still cost effective solution, but I am sure others have done similar. I believe this type of system is called a "hybrid system".

Solar panels charge a battery bank. The battery bank feeds an inverter with an split phase 240VAC output. Output feeds the "load". With the crappy amount of sun we get here in SE MI, especially during the winter, it would be very difficult (cost and size) to have a solar array and battery bank large enough to cover all loads. What is required is a transfer switch to switch the load from battery/inverter to PoCo line power when the battery bank is "low". At the same time, the line could optionally charge the battery bank. The PoCo also got permission to can their rates for a more expensive "peak" usage, so maybe charge the battery bank off peak ? Conceptually, this is the same as a mobile "all-in-1" inverter/charger/transfer switch.

Has anyone built a system like this and how well does it work ?

If I understand what you're looking for, this is how I use my Victron system. I don't sell anything back to the grid, I just use the grid as a "backup" when my batteries are low while solar recharges the batteries. While I don't regularly charge from the grid, I have the ability to do so if needed.

 

[Zwy]

Has anyone built a system like this and how well does it work ?

I run my house off grid until the batteries get low and it automatically switches to grid power. I can choose charging sources also, solar only, grid only, solar plus grid. The transfer switch is built into the units. I do not export anything to grid. I either use the power and store it or it just doesn't get captured. Dump loads such as home heating supplementation add to ROI and allow capturing some of the excess energy.

Most off grid all in one units have this function to switch to grid automatically. It was this function plus the availability of LFP batteries that made adoption of off grid micro grids a feasible option.

 

[theoldwizard1]

One challenge is system must support starting surge of loads.

I am well aware of this ! The A/C has the biggest starting load. A good soft starter, like a MicroAir 364/368 makes a HUGE difference in startup/LRA draw.

 

[JMACK61]

So in the midst of one of the cold snaps in recent memory here in SE MI I am think about solar power. A few years ago, the MI Public Service commission changed from "net metering" (hopefully the correct term) where the PoCo (DTE) would "buy back" any excess power from you, AT RETAIL RATES, until you had reached a "zero" bill. Now, they only buy back at commercial rates, making your cost recovery much, MUCH longer ! Plus, they have added a large number of other "steps" to getting hooked up, some at your expense, before you can "sell" any power back to the grid.

Gone are the days of just plugging a micro-inverter directly into an outdoor 120V receptacle ! I think I have come up with a still cost effective solution, but I am sure others have done similar. I believe this type of system is called a "hybrid system".

Solar panels charge a battery bank. The battery bank feeds an inverter with an split phase 240VAC output. Output feeds the "load". With the crappy amount of sun we get here in SE MI, especially during the winter, it would be very difficult (cost and size) to have a solar array and battery bank large enough to cover all loads. What is required is a transfer switch to switch the load from battery/inverter to PoCo line power when the battery bank is "low". At the same time, the line could optionally charge the battery bank. The PoCo also got permission to can their rates for a more expensive "peak" usage, so maybe charge the battery bank off peak ? Conceptually, this is the same as a mobile "all-in-1" inverter/charger/transfer switch.

Has anyone built a system like this and how well does it work ?

How you described the system should work is how my system work. My “Hybird inverters (I have two) are discarded UPS from work. I always had an old 3 kW SMA grid-tied inverter on my house that work great for saving me money during the day. 8 hours of California sun I turn it into stored battery power for the night. The charger is DIY too. I have current transducers on my L1 and L2 of my utility feed. The charger is a switch mode power supply (SMPS). I designed and programed it to charge the battery only with the extra power the grid-tie is making so while the Grid-tie is making 2.5kW’s and the house is using 400 watts the charger will automatically take the rest to the battery. I look at my utility meter and I see +/- 20 watts going to the grid. I use to feel good knowing that during the day I am not paying for Electricity so we do all our heavy load stuff Clothes Dryer and Dishwasher during the day. Now with the DIY powerwall we not paying for electricity at night. But I will be honest with you, winter time it‘s hard to keep up and we fall back on grid power before the sun comes up. It‘s okay just $20 to $40 a month.

 

[teal95]

I'm west of you in Consumers territory, but still operating under the same state laws.

We have an 8kW system that's old enough to be under the net metering rules. In December I got another 20kW system operational, but am still finishing up for inspections. SolArk 15k, 30 kW of EG4 LL batteries and 20 kW of panels on my barn roof. The roof peak is N-S so the aim isn't ideal, but neither is the amount of sun we get. (We finally had a bit of sun today and my 20 kW system just topped 9 kW peak.). I have it feeding a secondary "critical loads" panel in my house with the SolArk set to "limit to loads" and 40 W min grid draw. In this weather I'm rarely making it through the night without drawing the battery lower than I started but it's all uphill from here.