How do you install solar PV system for multi-family and multi-unit buildings?

    I am putting together a solar installation design for a multi-family building.   How do you let two units that have two service points from the grid share a single system?  How do you enable both units to benefit from the solar electricity generated from the system?

    Comments

    MG,

    I have a couple of questions:

    1. Does each unit have a dedicated meter or do they share a meter?

    2. When you say 'benefit', do you mean 'get net metering credit'?

    3. Is there only one roof between them with good irradiance?

    4. What state is the property in?

    - SFox

    SFox-

    1. In this particular application each unit has its own dedicated meter.
    2. When I say benefit what I really mean is that both units can share the power generated by the system.  I am assuming that only the system owner would be eligible for the rebate but each unit would reduce their power consumption through the output of the system.
    3. In this case their is only one roof and it does have good irradiance.
    4. This property is in CA however there is a second job I am working on in NY.

    Thanks for the help with this. 

    Michael

    Michael,

    Thanks for the clarification. The short answer is that if you have a PV system that generates more power than the meter it's connected to is using, then it goes into the "grid" - this is the basis for net metering that I'm sure you're aware of. The "grid" is the network of power supply and demand around the PV system. You're right about rebates - sort of - I'll add some more below. While the PV produced power would be consumed by the closest meters to the backfeeding meter, it would not have any effect on their recorded power consumption. The only benefit would be that renewable energy is being consumed close the the point of generation.

    As to the rebates or value of the PV power shared between multiple meters, things are very complicated and very political in nature. The technical term for this sharing is Virtual Net Metering. California is at the forefront of this policy - but only for limited cases:  The main reason it's so tricky (in my opinion) is that distributed power generation and virtual net metering is basically a direct threat to the established utility revenue models and the utilities are not going to change their way of doing business overnight. 

    If you want to keep up to date on renewable energy net metering policy, the best spot to start is DSIREUSE. Here are the links to California and NY:

    NY: Link

    CA:Link

    Hope this helps - it's an interesting topic and one you're sure to hear more about in the near future.

    Thanks for the answer on this, but I think the heart of the question that I have on this subject is, how do you wire a PV array such that two service boxes share the power generated by one array.  Is that possible?


    Thanks

    OK. That's not too hard. You could just use two smaller inverters (or micro inverters) which would divide the array into two separate sections (with two different outputs). One output could go to one meter and one output to the other. If the meters are on a common wall, it would be very easy. It would require one permit for each individual owner / address involved. The rebate or credits would be applied to each meter /account.

    - SFox

    Dan bergeron commented 7 months 2 weeks ago

    Have a duplex in MA interested in doing a PV lease. Is it possible to share the created electricity evenly to both units?

    Thank you for your great question. The simple answer is, yes, it is very possible using Virtual Net Metering (VNM). One company in CA that is doing this well is IV Energy Today their solution is only available in CA. Thanks again.

    Timothy J Smith commented 5 months ago

    i am trying to get solar installed in my owner occupied, two family home in Massachusetts. Each unit has a separate meter but the bills are both in my name. While taking bids for the project, several companies based the size of the proposed system on the average monthly usage for the building, figuring both unit's bills in together. but one company insisted that Massachusetts has a one meter rule that would limit the size of the system capacity to the average monthly usage of one meter (using the one with the higher bill of course). The size is then 13 kwh as opposed to a 27.9 kwh system that would cover both bills. Is this true, that Mass has a "one meter" capacity rule for multi-family homes?
    i understand that the system will only be connected to one net meter and that I can use virtual net metering to use the excess for the other bill, but a 13khw system would only cover about 10% of that.

    Submitted
    12 years 6 months ago
    Asked by
    Michael Goldberg
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    Installation
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