Solar noob sparky questions

[NoPlaceLikeOhm]

Hi,
I'm located in California (north Bay Area/Napa) PG&E and looking into solar.

I'm a licensed electrician (not active) and thinking about re-activating my license to do my own house. I never did solar, or residential (minus a few houses for friends) electrical.

I'm likely to use a design company to package up the planning/permiting/ submittal stuff, because I'm out of the loop and I do better with line diagrams and tools. I'm not a Hobbiest, nor do I want to tinker with it. I want to install it and be done, so I can get to the next item on my wife's list.

My questions for those in NorCal/PG&E are regarding the battery sizing to Number of panels and combined with a stand-by generator. I didn't really want to mess with batteries, but I'm understanding it has to do with the PG&E/grid connection makes it more worthwhile.

Given my recent quote from Renvu, for a 28 (480 watt) panel system (Enphase based) I'd like to minimize to only the necessary # of batteries and scale up later if possible. It was about double of what I was expecting, but it's a 'full system' racking/controllers/combiner/comms kit/micro-inverters/connectors a 5KwH battery/lumin smart panel. Which frankly, I don't know that most of that does. I thought I knew how to wire stuff too.

If there's anyone who has been through the diy solar in or close to my area I'd love to hear about your experiences with your project.

Thanks for any info.

 

[DIYrich]

Since you are doing it yourself, skip the enphase and go with an eg4 18kpv or solark 15k. Batteries will be way cheaper.

If you don't care about power when grid is down, then enough battery to store 1 day of production.

15kwh eg4 power pro is under $4,000, I think.

If you care about grid down, then 3 days of usage or a backup generator.

 

[Hedges]

See if Napa is using SolarAPP+

If so, and if your electrician (electrical contractor?) license meets the requirement and you get a city business license, you may be able to skip all drawings, just answer 101 questions on-line and submit machine generated data for permits.

SolarApp+

SolarApp+ From https://solarapp.nrel.gov/: Safe and affordable home solar through permitting automation In 2021, the National Renewable Energy Laboratory launched a collaborative effort with key code officials, authorities having jurisdiction, and the solar industry to develop standardized plan...

diysolarforum.com

As people here say, "Power Audit".
Know how many watts peak, how many watts motor starting surge, how many watt-hours/day summer and winter.
Then you can start to design a system.

You will be under NEM 3.0, which means paltry credit for backfeed except for a couple hours maybe between 6:00 and 8:00 PM when credit will be greater than retail. So you want to store all PV production for backfeed during those hours.

That means a battery with usable capacity equal to total production on best day of the year.
Off-grid, people may shoot for 3 days without sun. Since you're grid-backup, plan to conserve during such times.

PV panels are cheap (like $0.005/kWh amortized over 20 years), and batteries start around $0.05/kWh (amortized over their cycle life.) In other words, approaching 1/10th the cost of utility bills. Although complete system will be a bit more, maybe $0.10/kWh if all labor is free.

By telling PG&E you plan to add loads (electric heat, EV charging), you should be able to over-build and over-panel. Although, they may have a practice of verifying after the fact (so you could burn off surplus, I suppose.)

Equipment selection probably has to be UL Listed ESS. I understand EG4 18kpv + PowerPro qualifies, probably others but I'm not sure which.

 

[NoPlaceLikeOhm]

See if Napa is using SolarAPP+

If so, and if your electrician (electrical contractor?) license meets the requirement and you get a city business license, you may be able to skip all drawings, just answer 101 questions on-line and submit machine generated data for permits.

SolarApp+

SolarApp+ From https://solarapp.nrel.gov/: Safe and affordable home solar through permitting automation In 2021, the National Renewable Energy Laboratory launched a collaborative effort with key code officials, authorities having jurisdiction, and the solar industry to develop standardized plan...

diysolarforum.com

As people here say, "Power Audit".
Know how many watts peak, how many watts motor starting surge, how many watt-hours/day summer and winter.
Then you can start to design a system.

You will be under NEM 3.0, which means paltry credit for backfeed except for a couple hours maybe between 6:00 and 8:00 PM when credit will be greater than retail. So you want to store all PV production for backfeed during those hours.

That means a battery with usable capacity equal to total production on best day of the year.
Off-grid, people may shoot for 3 days without sun. Since you're grid-backup, plan to conserve during such times.

PV panels are cheap (like $0.005/kWh amortized over 20 years), and batteries start around $0.05/kWh (amortized over their cycle life.) In other words, approaching 1/10th the cost of utility bills. Although complete system will be a bit more, maybe $0.10/kWh if all labor is free.

By telling PG&E you plan to add loads (electric heat, EV charging), you should be able to over-build and over-panel. Although, they may have a practice of verifying after the fact (so you could burn off surplus, I suppose.)

Equipment selection probably has to be UL Listed ESS. I understand EG4 18kpv + PowerPro qualifies, probably others but I'm not sure which.

Thank you for the replies.

Looks like Napa is not a city that does the SolarApp+. Yes, Electrical contractor C-10 and B General.

Yep, I just want battery power for the night running Air Conditioning (I will add batteries in future when batteries become better and cheaper)

I might be overkilling the # of panels. My average usage during the summer is 54.8 KW/Day. But I anticipate this going up, as I'll add electric dryer/oven/water-heater/heat-pump/electric floor heat

I figured if I was messing around on the roof, just cover it once and be done, but I don't want to waste money if it's power I'll never use.

Is there a calculator to get the 'actual' amount of solar generated for my area and a given watt panel? I mean, 28 panels at 480 watts is 13.44KW, but what would that really generate, given average weather, loss, etc.

Thank you.

 

[EZPZ]

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

 

[Hedges]

I think this calculator just considers latitude and panel tilt/orientation:

Solar Irradiance Calculator

www.solarelectricityhandbook.com

I thought there was one that considers local weather, but didn't keep track of which.


I do believe in massively over-paneling. Panels are pretty cheap now. Trick is keeping mounting hardware economical.


Guess you'll have to draw up whatever the city wants. People here mention Greenlancer as an economical source of fancy plans. City may want roof truss details.


A/C at night is unfortunate. Wish that could be covered by heat exchanger to pool water or the like. At least hot side heat exchanger won't be as hot as in the day. Figure out how big a battery that requires.

The EG4 PowerPro battery looks attractive. Maybe one or two will cover your night time usage. Need to see the track record of its software reliability.
DIY is still significantly cheaper, if you are up for a project.

The other battery approach is to store PV production in a battery, then backfeed PG&E at NEM 3.0 credit rates during a couple hours of peak value (maybe 6:00 to 8:00 PM). Draw from PG&E at night. I'm not sure the ratio, but you might only have to store 50% of what you use at night, because credits buy you some 2x as many kWh as you gave them. (Storing and backfeeding more kWh than used at night lets you have credits for winter and overcast days.)

As I posted earlier, your total hardware cost should work out to $0.10/kWh, amortized over 20 years for PV and cycle life of 16 years for battery. Add time value of money, but still a fraction of utility rates. Probably saves you 75% compared to electric bill.

That is, until flat rate infrastructure pricing is introduced. Sliding scale, sticking it to the high earners.

 

[Kuma]

Did solar install last summer in Auburn California, Placer County. CPUC requires solar equipment be on their approved list. If youre hiring some one for design/planning they should be aware of this.

https://solarequipment.energy.ca.gov/Home/PVModuleList

Take your time buying anything. It may be best to wait until plans are approved. Many have bought equipment only to realize later it cant be used. I was close to that. Ordered large panels due to good price and later learned they will not fit due to roof setback requirements. Luckily the order was canceled anyway due to product availability.

PV Watts is good for estimate. Installed SMA string inverter and their design tool also provides monthly/annual solar output. Perhaps Enphase also has a design tool.

 

[NoPlaceLikeOhm]

I do believe in massively over-paneling. Panels are pretty cheap now. Trick is keeping mounting hardware economical.


Guess you'll have to draw up whatever the city wants. People here mention Greenlancer as an economical source of fancy plans. City may want roof truss details.


A/C at night is unfortunate. Wish that could be covered by heat exchanger to pool water or the like. At least hot side heat exchanger won't be as hot as in the day. Figure out how big a battery that requires.

The EG4 PowerPro battery looks attractive. Maybe one or two will cover your night time usage. Need to see the track record of its software reliability.
DIY is still significantly cheaper, if you are up for a project.

The other battery approach is to store PV production in a battery, then backfeed PG&E at NEM 3.0 credit rates during a couple hours of peak value (maybe 6:00 to 8:00 PM). Draw from PG&E at night. I'm not sure the ratio, but you might only have to store 50% of what you use at night, because credits buy you some 2x as many kWh as you gave them. (Storing and backfeeding more kWh than used at night lets you have credits for winter and overcast days.)

As I posted earlier, your total hardware cost should work out to $0.10/kWh, amortized over 20 years for PV and cycle life of 16 years for battery. Add time value of money, but still a fraction of utility rates. Probably saves you 75% compared to electric bill.

That is, until flat rate infrastructure pricing is introduced. Sliding scale, sticking it to the high earners.

Over paneling, was my thought just based on the panel prices and my cranky knees and back just wants to do it once.

Yes, I was shocked at the hardware/rack/mounting cost. Are panels all mounted the same way, i.e. would any racking work or is it not worth buying rack/mounts separately.

I have rafters, not trusses. I'm hoping that's not an issue, I guess it would be weight and wind-load. I might have struct-eng who might do me a favor, but I'd be banging nails in the attic, so I'm hoping not.

I'll likely farm out engineering on the solar, as I'll be replacing the main service too, and would prefer a paper/package I can submit to the city. The paperwork and code insanity is what burned me out of contracting.

I want a 400amp service(might even need it with a 13.4 Kw system?), but would rather buy and set-up 2-200amp panels for cost. Something like a 380v rated mast/meter box and split to each panel, but I know the bus rating has to be enough for the solar (some percentage) and I'm unsure if I can split the solar load to each panel or if it will even be necessary, or more costly to do that.

I really didn't want to break out the NEC book, and I'm guess mine is 2-3 editions too old. I might pay a local sparky for a code/consult/pre-inspection just to save time. He might even feel sorry for me, attic-ratting at 53. :D

Appreciate the info, it's helpful.

 

[NoPlaceLikeOhm]

Did solar install last summer in Auburn California, Placer County. CPUC requires solar equipment be on their approved list. If youre hiring some one for design/planning they should be aware of this.

https://solarequipment.energy.ca.gov/Home/PVModuleList

Take your time buying anything. It may be best to wait until plans are approved. Many have bought equipment only to realize later it cant be used. I was close to that. Ordered large panels due to good price and later learned they will not fit due to roof setback requirements. Luckily the order was canceled anyway due to product availability.

PV Watts is good for estimate. Installed SMA string inverter and their design tool also provides monthly/annual solar output. Perhaps Enphase also has a design tool.

Thank you Kuma, re: the list and the advice. I wasn't aware of that. I'll get it through the AHJ before I spend any on equipment.

 

[Hedges]

I'm putting in 15kW system, 64A requires 80A OCP. Upgrading from 100A panel to 200A (wire drop good for about 150A, utility worker said.)
I think I could have done it with 100A service/main breaker in 150A busbar panel (120% rule). But since it needed changing I upgraded.

Consider 200A service and 200A meter/main, fan out to 2x 200A sub panels & 1x 100A safety switch.
Unless you need to draw more than 160A continuous.

 

[NoPlaceLikeOhm]

I'm putting in 15kW system, 64A requires 80A OCP. Upgrading from 100A panel to 200A (wire drop good for about 150A, utility worker said.)
I think I could have done it with 100A service/main breaker in 150A busbar panel (120% rule). But since it needed changing I upgraded.

Consider 200A service and 200A meter/main, fan out to 2x 200A sub panels & 1x 100A safety switch.
Unless you need to draw more than 160A continuous.

Is the 'safety-switch' like a disconnect? To and from what?

Okay. I'd want a bit more of a cushion too.
So your math is : 15kw/240 = 62.5 amps --> 80amp breaker: 80x1.2 = 96 amps busbar rating (or greater)?

So mine would be at 13.4Kw/240 = 55.83 amps --> 60 amp breaker: 60x1.2 = 72 amp busbar rating. Unless I'm not understanding correctly.

200amp service. Mine might be close, but I don't know how frequently my 100amp welder, 5hp compressor and 2 A/C units will be running and a future E-vehicle plug would be going simultaneously.

 

[Hedges]

Visible blade safety switch is so PG&E can be absolutely, positively sure there is airgapped isolation between my PV generator and their grid.
(Alterative is they yank meter, let that be the airgap, and I'm left in the dark.)

Safety switch is between grid connection and PV inverter, or PV combiner box in my case.

Not understanding 120% rule correctly. It works like this:

If I replaced old 100A main panel with 150A busbar main panel having 100A main breaker,
150A x 120% = 180A
180A - 100A main breaker = 80A allowed PV breaker (or 2x 40A breakers).

I could connect 2x 7.68kW PV inverters to 2x breakers, but that is 4 wires so 2 or 3 wire safety switch wouldn't work.
80A backfed breaker in main panel, to safety switch, to PV aggregator panel with 2x 40A PV breakers.

While your PV is backfeeding, that reduces current draw from the grid. So during the day it will help with A/C.
If you put in something like SolArk or EG4 18kpv with battery, you could put CT at meter connection. Then it can peak shave to avoid exceeding 160A draw. It would pull from battery as needed, then charge battery from PV. And export from battery to grid during the couple hours credits are high.

 

[NoPlaceLikeOhm]

Visible blade safety switch is so PG&E can be absolutely, positively sure there is airgapped isolation between my PV generator and their grid.
(Alterative is they yank meter, let that be the airgap, and I'm left in the dark.)

Safety switch is between grid connection and PV inverter, or PV combiner box in my case.

Not understanding 120% rule correctly. It works like this:

If I replaced old 100A main panel with 150A busbar main panel having 100A main breaker,
150A x 120% = 180A
180A - 100A main breaker = 80A allowed PV breaker (or 2x 40A breakers).

I could connect 2x 7.68kW PV inverters to 2x breakers, but that is 4 wires so 2 or 3 wire safety switch wouldn't work.
80A backfed breaker in main panel, to safety switch, to PV aggregator panel with 2x 40A PV breakers.

While your PV is backfeeding, that reduces current draw from the grid. So during the day it will help with A/C.
If you put in something like SolArk or EG4 18kpv with battery, you could put CT at meter connection. Then it can peak shave to avoid exceeding 160A draw. It would pull from battery as needed, then charge battery from PV. And export from battery to grid during the couple hours credits are high.

Very cool. This helps a lot. Thank you.

So it's 120% of the bus rating, minus your main breaker. So a 13.44Kv system = 56 amps at 240v. I would just need to have
(busbar-rating) - (main breaker) > 56 amps. Am I understanding it correctly now?

Based on that, I likely wouldn't need to split the solar portion between 2-200amp panels. I guess,worse case, I could safety/knife switch 2-2 pole contactors disconnecting solar. Unless that wouldn't count as an airgap-break.

So the safety switch/knife-switch disconnects the entire array(s) from the panel/grid. The safety switch is required in addition to a transfer-switch?

Apologies for my ignorance. I'm just trying to picture a single line diagram of how the array/solar connection, 2-200 amp panels, standby generator panel and it's xfer switch (which could charge solar batteries if needed) all fit together/how they work.

I'm picturing: DC Solar Panels to micro-inverters ->PV-AC combiner -> PV-AC Safety/disconnect -> house panel -> batteries (charging) and feeding house loads.

But at night it's back-feeding the panel from the batteries -> house panel (what protects line-workers from my battery backed panel?)

Standby generator would simply feed a sub/emergency panel with a transfer-switch between house panel and sub/emergency panel (which would need to include the solar battery circuit to charge them off the genny.

Sorry for the mess I'm much better with pictures than words. I will have it engineered, but I'd like to understand the basics beforehand.

I do like everything I've read online about Solark.

 

[Hedges]

Very cool. This helps a lot. Thank you.

So it's 120% of the bus rating, minus your main breaker. So a 13.44Kv system = 56 amps at 240v. I would just need to have
(busbar-rating) - (main breaker) > 56 amps. Am I understanding it correctly now?

56A continuous x 1.25 margin for nuisance trips = 70A breaker.
Conveniently, 225A x 1.2 = 270, 270 - 200A main breaker = 70A PV breaker allowed by 120% rule, located at far end of busbar

100% rule is where busbar rating x 1.0 - main breaker = allowed PV breaker, located anywhere in panel. Less lenient, so not what you're likely to use. Not sure if it is necessary for center-fed busbar (main breaker in middle not end.)

Based on that, I likely wouldn't need to split the solar portion between 2-200amp panels. I guess,worse case, I could safety/knife switch 2-2 pole contactors disconnecting solar. Unless that wouldn't count as an airgap-break.

I don't think contactors would qualify, regardless of how you switched coil current.

So the safety switch/knife-switch disconnects the entire array(s) from the panel/grid. The safety switch is required in addition to a transfer-switch?

Visible blade DPDT transfer switch should qualify for disconnect.
Again, utility may be somewhat relaxed regarding requiring visible blade.

Apologies for my ignorance. I'm just trying to picture a single line diagram of how the array/solar connection, 2-200 amp panels, standby generator panel and it's xfer switch (which could charge solar batteries if needed) all fit together/how they work.

I'm picturing: DC Solar Panels to micro-inverters ->PV-AC combiner -> PV-AC Safety/disconnect -> house panel -> batteries (charging) and feeding house loads.

I'm not such a fan of microinverters, which are most convenient for system designers. I've only used high voltage string inverters (which now require RSD for rooftop.)

But at night it's back-feeding the panel from the batteries -> house panel (what protects line-workers from my battery backed panel?)

System may backfeed to house loads at night, CT at meter to hit nominally zero export. It would still do UL-1741 anti-islanding to protect linemen. Or open a relay to supply house loads during power failure if so equipped.

Standby generator would simply feed a sub/emergency panel with a transfer-switch between house panel and sub/emergency panel (which would need to include the solar battery circuit to charge them off the genny.

Sorry for the mess I'm much better with pictures than words. I will have it engineered, but I'd like to understand the basics beforehand.

Block diagrams are good for understanding and discussion.
I often draw with PowerPoint or draw, or free OpenOffice/LibreOffice alternative.

I do like everything I've read online about Solark.

SolArk uses HV string of DC coupled PV panels, supports Tigo RSD, can have AC coupled string or microinverters on "gen" port (not to exceed DC coupled.) It may do everything you want.

Also look at Midnight. Their Rosie and 10k AIO are new products, but the developers are highly regarded, pioneers of the industry.

 

[NoPlaceLikeOhm]

56A continuous x 1.25 margin for nuisance trips = 70A breaker.
Conveniently, 225A x 1.2 = 270, 270 - 200A main breaker = 70A PV breaker allowed by 120% rule, located at far end of busbar

100% rule is where busbar rating x 1.0 - main breaker = allowed PV breaker, located anywhere in panel. Less lenient, so not what you're likely to use. Not sure if it is necessary for center-fed busbar (main breaker in middle not end.)




I don't think contactors would qualify, regardless of how you switched coil current.



Visible blade DPDT transfer switch should qualify for disconnect.
Again, utility may be somewhat relaxed regarding requiring visible blade.



I'm not such a fan of microinverters, which are most convenient for system designers. I've only used high voltage string inverters (which now require RSD for rooftop.)



System may backfeed to house loads at night, CT at meter to hit nominally zero export. It would still do UL-1741 anti-islanding to protect linemen. Or open a relay to supply house loads during power failure if so equipped.



Block diagrams are good for understanding and discussion.
I often draw with PowerPoint or draw, or free OpenOffice/LibreOffice alternative.



SolArk uses HV string of DC coupled PV panels, supports Tigo RSD, can have AC coupled string or microinverters on "gen" port (not to exceed DC coupled.) It may do everything you want.

Also look at Midnight. Their Rosie and 10k AIO are new products, but the developers are highly regarded, pioneers of the industry.

Jeeze, it seems the more I learn about additional components/design option the more confusing it is to make/build the ideal system.

If I’m correct, the solark hybrid has the inverter/controller for power and batteries and standby generator all packaged in one unit.

I’d assume without micro-inverters (I’m all for less components to break down) I would be running larger gauge wire/larger conduit roof penetrations going DC from roof to solark.

High voltage to me is over 600vac, what is solar high-voltage?

I really don’t understand the point of emergency switches on the roof for firefighter safety, you can turn off the ac/inverter but the panels themselves are still generating power in DC in daylight. I suppose DC is a bit safer/lower voltage.

I’d really like to find a California specific solar-designer/plan-submittle package as the state has gotten so mired in ridiculous code/fear of liability it’s crippling.

Thank you

 

[Hedges]

I mean "high" voltage not exceeding 600V, residential/rooftop. Some commercial units go to 1000V/

RSD isolates between panels so instead of < 600V between wires it is < 80V between wires. Supposed to be safer for firemen, but maybe not soaking wet.
More likely, it was lobbied for by Enphase.

Microinverters means 240Vrms at higher current.
PV strings could be as low as 100V, but mine are 480Voc, 380Vmp.

Now is your chance to plan your alternative energy future including PV and batteries, before you paint yourself into a corner.

I'm planning Sunny Boy or Sunny Boy Smart Energy for my sister, optional BYD LiFePO4 battery optional Automatic Backup Unit. More expensive and wimpy surge.

For myself, Sunny Boy, Sunny Island, AGM battery.

Midnight says their batteries will be very competitive. Watch that space, might be good for you.

EG4 and SolArk are available now, have "different" reputations.

If you need an installer, you'll be constrained to a couple volume brands of equipment.

 

[TomasGrey]

See if Napa is using SolarAPP+

If so, and if your electrician (electrical contractor?) license meets the requirement and you get a city business license, you may be able to skip all drawings, just answer 101 questions on-line and submit machine generated data for permits.

SolarApp+

SolarApp+ From https://solarapp.nrel.gov/: Safe and affordable home solar through permitting automation In 2021, the National Renewable Energy Laboratory launched a collaborative effort with key code officials, authorities having jurisdiction, and the solar industry to develop standardized plan...

diysolarforum.com

As people here say, "Power Audit".
Know how many watts peak, how many watts motor starting surge, how many watt-hours/day summer and winter.
Then you can start to design a system.

You will be under NEM 3.0, which means paltry credit for backfeed except for a couple hours maybe between 6:00 and 8:00 PM when credit will be greater than retail. So you want to store all PV production for backfeed during those hours.

That means a battery with usable capacity equal to total production on best day of the year.
Off-grid, people may shoot for 3 days without sun. Since you're grid-backup, plan to conserve during such times.

PV panels are cheap (like $0.005/kWh amortized over 20 years), and batteries start around $0.05/kWh (amortized over their cycle life.) In other words, approaching 1/10th the cost of utility bills. Although complete system will be a bit more, maybe $0.10/kWh if all labor is free.

By telling PG&E you plan to add loads (electric heat, EV charging), you should be able to over-build and over-panel. Although, they may have a practice of verifying after the fact (so you could burn off surplus, I suppose.)

Equipment selection probably has to be UL Listed ESS. I understand EG4 18kpv + PowerPro qualifies, probably others but I'm not sure which.

thanks!

 

[glandpuck]

I'm in So Cal and have a lot of experience with a system I had designed and installed and revised. I do not sell anything. I do not receive any commission. If you want to talk and get free advice and some sources in CA for hardware, then send me a PM.

The biggest problem you will have in doing this yourself is the lack of experience in doing it. I know you can bend the conduit, make the right choices of sizes, wire gauges, etc. But the key is knowing what are the best components to select to make it easy to install and to service and upgrade. And most importantly sizing the system to actually do what you want it to do. with NEM 3.0, there is no reason to sell to your utility provider. they don't want your wattage. They are busy expanding their own infrastructure and building massive battery storage facilities and lobbying the state for higher rates to build it all out and try to prevent fires.

So if you proceed, you are going to want to focus on a self consumption design, enough storage from batteries to offset time of use rates and get you through a 24 hour period on batteries. If you want a generator and plan on living for more than the next 10 years, I would highly advise a diesel generator, preferably liquid cooled which you can run forever even without your utility ever coming online. Second to that, a liquid cooled propane gen set and lastly air cooled or a large portable that burns propane.