Massachusetts National Grid Qualifying Facility (QF) P-Rate Question

[TORQU3]

I put down a deposit in October of 2020, the system is still not installed, but thats a different story. Tesla has been the delay not permitting. National Grid is currently reviewing everything for interconnection approval then we can schedule install.

The system is 39 340watt panels, (2) powerwall+ units and (2) powerwall 2's. Annual output should be right in line with my annual consumption. Originally the system was planned to have a 10kW SE inverter but Tesla has been phasing those out in favor of their own inverters or powerwall+ units. I would have qualified for the net metering cap exemption with the 10kW SE inverter but I do not with the new proposed system with an inverter size of 15.2kW. Also, the net metering allocation is full at the moment, MA ACA confirmed I would be on a waitlist if I applied.

Given that scenario, I understand it it will be considered a "Qualifying Facility" or QF (and the NG application says so). I will be selling any excess production at the "P-Rate" tariff which I think is tied to the hourly ISO-NE wholesale rate. I understand the wholesale rate is usually around 3 cent's per kWh, but it varies. For comparison the retail rate usually hovers around 25 cents and fixed for each season.

This publication leads me to believe the production or consumption is netted on an hourly basis and credited or billed as such. Monthly netting would be much more beneficial, but that doesn't seem to be the case.
Qualifying facilities and on-site generating facilities

That would mean I would really want to be using power as is it produced or charge the power walls for future consumption as selling to the grid is 10x less compensation as the rate to buy. Is my understanding correct?

Does the SMART compensation play into this at all? I know there is a line item subtracted for the "value of the energy", which when you are part of net metering it's the full retail rate. If you aren't part of net metering is the fairly low wholesale rate subtracted instead? This would mean a larger SMART compensation to offset to low wholesale p-rate tariff sell rate? I really haven't been able to get a clear explanation from anyone at Tesla or the MA ACA or SMART etc when I called them.

I want to be sure I'm understanding how everything is billed/credited so I can utilize my power walls and when we consume power to maximize the financial impact of the electricity produced.

 

[solarAddict]

Unfortunately I have no answers for you this time as my system is below 10kW limit and everything (well. mostly) is straight forward. I was just thinking that you might need to verify one more thing - when you get into net metering. If I remember correctly someone mentioned that if you are above 10kW limit, your metering works differently - there is a time cap on the period you can accumulate 'credits'. Again, this is hearsay that I read once here - it made me call to NG to verify if this rule applied to my setup as well (luckily it does not).
Wish I could be mere of help ..

 

[adspguy]

I can’t really answer your questions from my experience as I am at 10kW generation. But since SMART compensation is based solely on the separate generation meter I bet they don’t adjust the value based on your unfavorable net metering situation. When I got my statement of qualification for SMART it quoted the reimbursement rate as a constant. It is not recalculated on each billing period, just on the block you qualified for. They don’t adjust it based on if I use the electricity or it goes back to the grid. Part of the whole purpose of SMART was to guarantee a fixed rate of reimbursement. Maybe it is different for the larger systems though.

Will you be able to join connectedsolutions? The cash flow from that is significant, but in your case it might be better for you to use the powerwalls to offset the difference in net metering rates. In my case, during a connectedsolutions event, the powerwalls will charge at the full solar generation rate and the house gets powered by the grid. This is different from when it is not in an event and the powerwalls only charge at the generation minus house use rate. That would suck in the net metering paying wholesale rate back as the discharge of the powerwalls back to the grid would be at the lower rate. it Is like charging the powerwalls from the grid at retail and selling it back at wholesale, not a good thing at all. With 1:1 net metering it is not a bad trade since the connectedsolutions payout easily overcomes the powerwalls charge/discharge loss.

 

[TORQU3]

I will be participating in connected solutions, it was the only way I could really justify buying the power walls at all, never mind 4 of them. The whole billing side, when not eligible for net metering, seems like it could be complicated and no one has been able to clearly state how it will work. I think I know how it will work from the reading I have done, but I'm not certain.

I kept pushing Tesla to keep the 10kW SE inverter in the design because I knew how net metering worked and knew it was the best way for my system to be designed. There would be so little clipping that it wouldn't really be a big deal. I'm surprised Tesla didn't make a software limited inverter where each one is 5kW so it could be stacked and still comply with MA net metering exemption limit. I believe some other states have a similar limit. I had to keep reminding them of this....In the end I didn't want to delay my project any more so I just went with the Tesla powerwall+ units.

I still can't believe we are 10 months into this process and still nothing is installed. I was told February/March timeframe we should have the hardware installed.

 

[TORQU3]

I found this document, which is a bit old but may still be accurate. It looks like power will be netted on a monthly basis and the average ISO-NE wholesale rate will be used if you are a QF less than 60kW. So maybe day to day, hour by hour production vs compsumtion variation won't matter too much.