4 tenants, 1 60kW solar array - possible to run 4 AC outputs from single inverter?

B

Brettstep

Member
Location
Ohio
Occupation
Solar Developer
I have a 3-phase commercial building with 4 tenants that my client wants to serve with 1 solar array. Is there anyway to have 4 AC outputs coming out of one inverter, doing to 4 MDP's? Was thinking I could put CT's on each run to account and bill for the solar power being consumed by each tenant.
 
Brettstep said:
I have a 3-phase commercial building with 4 tenants that my client wants to serve with 1 solar array. Is there anyway to have 4 AC outputs coming out of one inverter, doing to 4 MDP's? Was thinking I could put CT's on each run to account and bill for the solar power being consumed by each tenant.
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No.
 
Brettstep said:
I have a 3-phase commercial building with 4 tenants that my client wants to serve with 1 solar array. Is there anyway to have 4 AC outputs coming out of one inverter, doing to 4 MDP's? Was thinking I could put CT's on each run to account and bill for the solar power being consumed by each tenant.
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You cannot split up a single output.

Otherwise it's more of a legal question than a technical one.

If these tenants are metered by the utility then whether you can legally do anything like what the client wants depends on whether they allow a utility meter with solar to credit other meters on the same service or property. Most states don't have favorable laws on this.

If the tenants are legally submetered and your client pays a master utility meter, then I'd presume the client takes the savings and doesn't have to change how he charges the tenants.
 
LarryFine said:
Welcome to the forum.

Won't they end up in parallel anyway?

Why not just meter each tenant's power usage?
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Thank you for the welcome and your thoughts. I am not sure the implications of ending up in parallel. Sorry, I am more of a developer than electrician. Just looking for the most cost effective and allocation effective way to design. Right now the client is rehabbibg the commercial building that has no tenants, so no prior usage to size each of the systems appropriately based on what can be widely variant tenant energy needs. Having 4 seperate systems sized equally may result in some tenants being under supplied and some over. The other downside is having 4 seperate accounts, 4 seperate customer charges, 4 seperate home runs, 4 seperate inverters....and not have the one system to more effectively address the peak demand spikes of any one tenant.
 
jaggedben said:
You cannot split up a single output.

Otherwise it's more of a legal question than a technical one.

If these tenants are metered by the utility then whether you can legally do anything like what the client wants depends on whether they allow a utility meter with solar to credit other meters on the same service or property. Most states don't have favorable laws on this.

If the tenants are legally submetered and your client pays a master utility meter, then I'd presume the client takes the savings and doesn't have to change how he charges the tenants.
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Thank you for thoughts. Ohio does not have the virtual net metering you suggested, which would be the most effective option. Any difference in having 4 inverters, with each output going to each tenants main panel, vs just splitting output from one 50kW inverter? The client ideally wants to bill his tenants for the solar energy they use, vs trying to estimate how much more they should pay in rent for significantly reduced electric bills from the solar.
 
Brettstep said:
Thank you for thoughts. Ohio does not have the virtual net metering you suggested, which would be the most effective option. Any difference in having 4 inverters, with each output going to each tenants main panel, vs just splitting output from one 50kW inverter?
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Yes,that's totally different in just about every respect.

The client ideally wants to bill his tenants for the solar energy they use, vs trying to estimate how much more they should pay in rent for significantly reduced electric bills from the solar.
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He should probably look into whether and how that is legal.
 
Brettstep said:
Thank you for reading and answering. Any thoughts on this Solshare tech.... https://allumeenergy.com/us/how-it-works/
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Sorry for my terse reply, but there isn't a whole lot of information in your question and the reasons for my answer depend on the service design. For one thing, if the tenants are separately metered you can't connect them to the same PV inverter because the branch point at the inverter would provide a current path from one tenant's service to another tenant's loads.

Something you might consider is to build the PV system with microinverters; you can split them up any way you want.
 
Brettstep said:
Thank you for the welcome and your thoughts. I am not sure the implications of ending up in parallel. Sorry, I am more of a developer than electrician. Just looking for the most cost effective and allocation effective way to design. Right now the client is rehabbibg the commercial building that has no tenants, so no prior usage to size each of the systems appropriately based on what can be widely variant tenant energy needs. Having 4 seperate systems sized equally may result in some tenants being under supplied and some over. The other downside is having 4 seperate accounts, 4 seperate customer charges, 4 seperate home runs, 4 seperate inverters....and not have the one system to more effectively address the peak demand spikes of any one tenant.
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As you found we do not have virtual metering in Ohio, and to my knowledge it is not legal to sub-meter tenants in a commercial building from a single service. But what we commonly do have in Ohio for commercial and industrial customers is demand charges, which may or may not currently apply to the building you are describing. If there are kW demand charges, then there is no practical way to sub-meter that, even if you could pursue sub-metering the kWh usage by changing to a single service and installing CT's on feeders to each individual customer. What might be legal, not sure, is to change the lease agreement for the tenants to state that electric is included in the lease, with the stipulation that there is some schedule of annual kWh usage included, and if their usage is below it, they get a certain amount of lease credit, and if their usage is above it, they pay a certain additional fee. If this is indeed legal, the complication is you would need to set those thresholds without knowing how much a tenant will use, and if there are demand charges for the service from the utility, this would complicate things enough to make it not feasible. There is a community solar bill being worked on in Ohio, and if it passes and does not contain any poison pills that render it useless, that might be your solution, to install solar on the common roof and sell subscriptions to each tenant. Of course, the demand charge issue still potentially could make this less desirable.
 
solarken said:
As you found we do not have virtual metering in Ohio, and to my knowledge it is not legal to sub-meter tenants in a commercial building from a single service. But what we commonly do have in Ohio for commercial and industrial customers is demand charges, which may or may not currently apply to the building you are describing. If there are kW demand charges, then there is no practical way to sub-meter that, even if you could pursue sub-metering the kWh usage by changing to a single service and installing CT's on feeders to each individual customer. What might be legal, not sure, is to change the lease agreement for the tenants to state that electric is included in the lease, with the stipulation that there is some schedule of annual kWh usage included, and if their usage is below it, they get a certain amount of lease credit, and if their usage is above it, they pay a certain additional fee. If this is indeed legal, the complication is you would need to set those thresholds without knowing how much a tenant will use, and if there are demand charges for the service from the utility, this would complicate things enough to make it not feasible. There is a community solar bill being worked on in Ohio, and if it passes and does not contain any poison pills that render it useless, that might be your solution, to install solar on the common roof and sell subscriptions to each tenant. Of course, the demand charge issue still potentially could make this less desirable.
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But of course PV does not dependably affect demand charges.
 
jaggedben said:
I think he was alluding to that. Demand charges make the whole thing less desirable.
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I didn't read what he posted in great detail, but whenever I see "PV" and "demand charges" together I feel a need to point out that PV doesn't necessarily help with demand because so many people don't seem to get that.
 
ggunn said:
I didn't read what he posted in great detail, but whenever I see "PV" and "demand charges" together I feel a need to point out that PV doesn't necessarily help with demand because so many people don't seem to get that.
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I agree with you and jaggedben, and I have been working a lot lately on potential projects for customers with high demand charges. How much solar helps comes down to the daily load profile of the business. If peaks happen mid-day, solar will help more, if they happen at 6:00am when the factory crew arrives, solar will help far less. I get interval data from the utility whenever I can, and then can model it with some level of confidence. Same applies for assessing how much storage is needed to peak shave. But you are right, a lot of people don't get that.
 
solarken said:
As you found we do not have virtual metering in Ohio, and to my knowledge it is not legal to sub-meter tenants in a commercial building from a single service. But what we commonly do have in Ohio for commercial and industrial customers is demand charges, which may or may not currently apply to the building you are describing. If there are kW demand charges, then there is no practical way to sub-meter that, even if you could pursue sub-metering the kWh usage by changing to a single service and installing CT's on feeders to each individual customer. What might be legal, not sure, is to change the lease agreement for the tenants to state that electric is included in the lease, with the stipulation that there is some schedule of annual kWh usage included, and if their usage is below it, they get a certain amount of lease credit, and if their usage is above it, they pay a certain additional fee. If this is indeed legal, the complication is you would need to set those thresholds without knowing how much a tenant will use, and if there are demand charges for the service from the utility, this would complicate things enough to make it not feasible. There is a community solar bill being worked on in Ohio, and if it passes and does not contain any poison pills that render it useless, that might be your solution, to install solar on the common roof and sell subscriptions to each tenant. Of course, the demand charge issue still potentially could make this less desirable.
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Yes, the rate plan would include demand charges. Curious why you think that makes it impractical to submeter? Are submeters like this, https://www.satec-global.com/BFM136 , not capable of measuring the kW, but only kWh's? If it could measure the peak consumption to each subpanel/tenant, then couldn't peak demand just be allocated accordingly? I will call the state about legality. Not sure how a landlord submetering/selling solar power to tenants is different than a solar company selling solar power to customers via PPAs? I appreciate your idea on the lease agreement. Yes, I too am hoping the community solar bill will eventually get passed.
 
solarken said:
I agree with you and jaggedben, and I have been working a lot lately on potential projects for customers with high demand charges. How much solar helps comes down to the daily load profile of the business. If peaks happen mid-day, solar will help more, if they happen at 6:00am when the factory crew arrives, solar will help far less. I get interval data from the utility whenever I can, and then can model it with some level of confidence. Same applies for assessing how much storage is needed to peak shave. But you are right, a lot of people don't get that.
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But if a peak happens when the PV is not producing, like on a dark cloudy day or at night, there's your demand charge.
 
ggunn said:
But of course PV does not dependably affect demand charges.
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Totally understand PV does not dependably affect demand charges...but in a typical 9-5 operation with 4 tenants, each tenant has a better chance of having their demand reduced by having the potential capacity of a 60kW array vs the potential capacity of only 15kW - which they would only have if we had seperate meters and seperate solar arrays going to each meter. With energy rates as high as they are now, and solar costs as low as they are, along with the stack of other grants and incentives, peak demand savings are not necessary for the project to have a great ROI...but I still like to optimize for the demand savings if possible.
 
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