net metering regulations for MA?

[k.electron]

Planning to get a 14-15kwdc system with the solaredge 10kwac inverter. I know that only 10kwac or less is allowed for 1:1 net metering in MA. Today I heard something about systems can only be scaled to 115% of yearly usage to be eligible, otherwise its a 18-24 month wait for net metering. since we just bought the house, we dont have a years worth of bills. Consultant said that the utility company will use neighborhood average / sq ft to estimate in the absence of bills.

can someone point me to this net metering restriction? 14-15kwdc is about 150% of what they are claiming is neighborhood average / sq ft.

[Markyrocks69]

Umm just bc you don't have the old Bill's shouldn't be an issue. Call the electric company, tell them you just bought the property. (I'm assuming that the bill is now in your name) they shouldn't have a problem telling you the history of usage of the property. I could be wrong but would think they would just include that information on the bill anyways. Not like its secret information or something. Is there any particular reason you want such a large system? Usually the system size is based off of the usage. If you have a gas furnace and other gas appliances I'd assume that youd more than likely be fine with 10kw of panels and a 7.7kw inverter. But I could be way off.

7.7 is kinda the lucky number bc it simplifies the installation requirements for a 200amp main service. Anything above that is going to be trickier and most likely more expensive.

[k.electron]

ok other providers are saying there is no such requirement so im wondering if this was some sort of sales tactic.

we currently live in a condo that is half the area and go through about 9MWH in a year. when we move into our single family, my parents will live with us too. we dont have gas so its all electric stove (used everyday for 5 person meals), electric oven, electric dryer. we are getting a mini split heat pump system installed so its going to take the edge off oil in the winter as well. additionally im expecting my tesla m3 to consume about 4.5MWH in the year based on current usage patterns. so in all we estimate using about 15MWH+ of power in the year.

[Markyrocks69]

ok other providers are saying there is no such requirement so im wondering if this was some sort of sales tactic.

we currently live in a condo that is half the area and go through about 9MWH in a year. when we move into our single family, my parents will live with us too. we dont have gas so its all electric stove (used everyday for 5 person meals), electric oven, electric dryer. we are getting a mini split heat pump system installed so its going to take the edge off oil in the winter as well. additionally im expecting my tesla m3 to consume about 4.5MWH in the year based on current usage patterns. so in all we estimate using about 15MWH+ of power in the year.

If I were you I'd figure out which electric company you will have servicing your new house. There website should list all the requirements for interconnection of solar generation. Look at the requirements for yourself. If the consultant is from a solar company that services the area where you're planning to have the system installed I'd assume that they're familiar with the rules of that area.

My house is also all electric and we use about 20mwh a year and I don't have a tesla and my house is tiny so you honestly may be underestimating. That's why it would still be useful to have the previous usage of the property. Besides that you may be forced to install a smaller system now and upgrade it later if the rules you're describing are in fact the rules for the area. It might not be ma specific it has to do with the exact electric company that your using.

[JSchnee21]

It's generally true for most residential grid tie agreements that system size is limited such that one might reasonably expect the solar PV system to produce no more than ~100% (e.g 90-110%) of historical usage (that is to say, net zero). Additionally, some PoCo's may have further limitations which cap residential system size at 10kW or 12kW or 15kW or similar before you transition into the next higher PV electric generator tier which may come with added requirements and costs, not the lease of which is liability insurance.

If this is not new construction, then the PoCo should have historical electrical bills for this property. Or, you could nicely ask the people you bought it from.

The next question is whether or not your AHJ will permit a LINE Side Tap. Assuming you have a 200amp panel, LOAD side taps are limited to the 120% rule, or ~7.6kW in most cases. But, on the East coast, many jurisdictions permit line side taps (mine does in NJ). TYPO CORRECTED.

Finally, you'll need to consider the orientation and inclination of your roof planes (with your future installer) to understand the percentage of inverter over subscription that makes sense. And the anticipated production of said system -- though you can model this yourself as well if you're ambitious.

On my interconnect agreement, from JCPL, there was a section where the installer had to estimate the expected production and demonstrate that it was "reasonable" based on last years consumption. But, the extent to which these calculations were or were not scrutinized I could not say. My installer estimated a bit low.

But every PoCo interconnect agreement differs. Call your PoCo and get a copy.

Not sure how big your home is, but 14-15kW is a pretty big residential system. Mine is 12.2kW for comparison (~2100 sq feet) but I have some shade and poor roof inclination (only 20%). I also use a lot of air conditioning, but most of my major appliances, heat, etc. are natural gas. Given the propensity for rain/snow/clouds in MA, while you may have less HVAC requirement, if you anticipate one or more electric cars, I could potentially see needing 14-15kW. Especially if you have any electric appliances.

[ButchDeal]

The next question is whether or not your AHJ will permit a Load Side Tap. Assuming you have a 200amp panel, line side taps are limited to the 120% rule, or ~7.6kW in most cases.

This is actually backwards. Load side tapes are limited by 120% rule and are generally limited to a 7.6kW system on a 200a MSP with 200a bus.

Line Side tap is not limited though.

[Markyrocks69]

This is actually backwards. Load side tapes are limited by 120% rule and are generally limited to a 7.6kW system on a 200a MSP with 200a bus.

Line Side tap is not limited though.

A line side tap is limited to the ampacity of the service entrance cable. If you have 200amp wire they won't allow 400amps worth of solar but I doubt any residential installation would ever exceed the 200.

However when you said load side tap does this normally refer to just interconnection at a breaker in the panel? I suppose its possible to tap say a 60amp wire for some appliance circuit but when someone says load side tap they're referring to a tap that would inevitably land on the bus of a main distribution panel?

[ButchDeal]

A line side tap is limited to the ampacity of the service entrance cable. If you have 200amp wire they won't allow 400amps worth of solar but I doubt any residential installation would ever exceed the 200.

However when you said load side tap does this normally refer to just interconnection at a breaker in the panel? I suppose its possible to tap say a 60amp wire for some appliance circuit but when someone says load side tap they're referring to a tap that would inevitably land on the bus of a main distribution panel?

most services with a 200a MSP have a higher amp service often 350 or higher but yes you are correct, the Line side tap would be limited by the service NOT MSP size which would generally be a lot higher than a 40a limit for a 7.6kW inverter as stated above by JSchnee21.

A load side tap would generally be a breaker in the MSP or something on the load side of the MSP not the LINE or SERVICE side of the MSP.

[JSchnee21]

Sorry, yes, that was a typo on my part. --- CORECTED

[k.electron]

im not a 100% sure what this tap business is, but i couldnt find any documentation about this 115 limit. no other provider seems to know anything about it either.

given that we estimate about 15-17 mwh per year, we are most likely going to go with a provider that will put up a 15.2 kwdc system with the 10 kwac solaredge.

[Markyrocks69]

im not a 100% sure what this tap business is, but i couldnt find any documentation about this 115 limit. no other provider seems to know anything about it either.

given that we estimate about 15-17 mwh per year, we are most likely going to go with a provider that will put up a 15.2 kwdc system with the 10 kwac solaredge.

Well the first piece of information that you probably need to find out is what is the maximum output in amps from your inverter. Usually the breaker is that number x 1.25.

If your main service panel is a 200amp service more than likely the biggest breaker that you can use to backfeed into the panel is 40 amp double pole. If it's only 100amp service your limited to 20... in a nutshell ( this is not precise) your main distribution panel amp rating on the bus, say 200 x 1.2=240 (120%). 240amps would be the maximum input amps from all sources. Now you could put in a smaller main breaker or other various tricks to play with the numbers ect. Anything else is going to require a line side tap.

Read this it will explain it in more detail

https://www.jadelearning.com/2014-nec-705-12d2-understanding-pv-interconnections/

[brianbsl]

Is it National Grid or Eversource?

National Grid has a form you can fill out to qualify by the load you have in your house (number of lights, fridges, etc).
However my installer didn't require that even though we were applying about 25% higher than our past 12mo of usage and National Grid pushed it right through (like within 24 hours).
I was getting all wound up over it and it was a total non-issue.

We do have CL320 service which maybe helped justify it. And we had only been there for about a year and I believe the owners had a much higher usage (we swapped out 180 incandescent bulbs for LED for example).

[k.electron]

Is it National Grid or Eversource?

National Grid has a form you can fill out to qualify by the load you have in your house (number of lights, fridges, etc).

we have national grid.

qualify for what? net metering at all? or just cap allocation? as a 10kwac system we dont need cap allocation.

[k.electron]

Well the first piece of information that you probably need to find out is what is the maximum output in amps from your inverter. Usually the breaker is that number x 1.25.

If your main service panel is a 200amp service more than likely the biggest breaker that you can use to backfeed into the panel is 40 amp double pole. If it's only 100amp service your limited to 20... in a nutshell ( this is not precise) your main distribution panel amp rating on the bus, say 200 x 1.2=240 (120%). 240amps would be the maximum input amps from all sources. Now you could put in a smaller main breaker or other various tricks to play with the numbers ect. Anything else is going to require a line side tap.

Read this it will explain it in more detail
https://www.jadelearning.com/2014-ne...erconnections/

solaredge se10000h-us is rated at 42A continuous output at 240V. we have a 200A panel.
even at 125% we should be more than adequate here.

[brianbsl]

we have national grid.

qualify for what? net metering at all? or just cap allocation? as a 10kwac system we dont need cap allocation.

To justify your usage. If your history does not justify it.