Solar on the shady side of the roof

[Calsun]

Many installations have sections of panels that produce a different amount of power during the day and this is handled by a dual MPPT charge controller equipped inverter. This type of inverter is quite common today but was rare when I installed solar on my house in 2012. Many inverters have 4 MPPT charge controllers and can handle 4 different arrays with no problem and one still has a single inverter box.

I was focused on the panel arrays on my house and largely ignored the inverter specifications. When I replaced the Sunpower inverter (which failed under warranty but with Sunpower dragging their feet to replace it for the past 4 months), I did so with a Solis dual MPPT inverter that has provision for adding battery backup later with the batteries charged by the inverter, easy addition of Wifi for both internet and smartphone connectivity, and many other features not in my original inverter. I would strongly recommend giving full consideration to the inverter that the dealer is selling you.

When I interviewed 4 solar installation companies the one I chose was the one whose people were willing and able to work with me. The other 3 had hired salespeople who were clueless and selling solar as they might sell home siding.

[J.P.M.]

NW/SE is 12 deg, NE/SW is 20 deg.

Thank you once again.
The low tilts help explain the relatively small difference in outputs as f(orientation).

[davidcheok]

If I were going to install solar that was only going to knock 7% off my bill, I rather put that money elsewhere.

[OCJ]

Forgot to ask: What's the tilt of the panels ?

Thanx,

J.P.M.

NW/SE is 12 deg, NE/SW is 20 deg.

[J.P.M.]

They're 400s. SE is at 147 deg and the other panels offset by 90 deg. $2.50 /watt installed.

The 5 NE panels at 57 deg are set to do at least 2,500 kWh for the year, $5k pre-incentive, $3.5k post, thanks SDG&E for the ridiculous sub 4-year payback on Northerly facing panels. And that was before the January price increase!

Forgot to ask: What's the tilt of the panels ?

Thanx,

J.P.M.

[OCJ]

What's the STC rating of the panels ?

They're 400s. SE is at 147 deg and the other panels offset by 90 deg. $2.50 /watt installed.

The 5 NE panels at 57 deg are set to do at least 2,500 kWh for the year, $5k pre-incentive, $3.5k post, thanks SDG&E for the ridiculous sub 4-year payback on Northerly facing panels. And that was before the January price increase!

[J.P.M.]

I have NE and NW panels in SoCal, normally that would be a bad idea and yes winter production sucks, but thanks to SDG&E somehow reaching this far north with their sky high pricing and the magic of NEM 2.0, the summer generation carries the year.

I have Powerwall Dashboard and Home Assistant running in VMs as well as an Emporia Vue Utility Connect, and I've downloaded and summed 4 PVWatts runs (SE, SW, NE, and NW) hourly data into Excel to compare with actuals, as well as Green Button data and CSV import from the Tesla app.

Last June 24th (day after PTO, first day after solstice that wasn't throttled) I was able to record a full day of production. My NE panels produced 2.50 kWh each, NW panels 2.80 kWh each, SE 2.71 kWh each, and SW 2.76 kWh each.

Now fast forward to Winter solstice, NE was 676 Wh each, NW 1.1 kWh each, SE was 1.54 kWh each, and SW was 1.07 kWh each.

Now one thing is my NW and SW panels are paralleled in a string. So while my SW production seems to be "brought down" my NW production seems to be "brought up."

And finally production from June 24th to Dec 24th looked like this: NE 254 kWh each, NW 326 kWh each, SE 350 kWh each, and SW 328 kWh each.

So while not completely North or South, my Northerly production was certainly worth it for me and I would still get those panels if I had to do it again. For my location, PVWatts puts North production at 69.5% of South production, with only azimuth changed. PVWatts has proven fairly accurate for my system so far.

What's the STC rating of the panels ?

[OCJ]

I am glad those Northern panels are working for you. Most end up spending a lot more then that kind of panel can produce making the payback very long and hard. Hopefully you will reduce your electric bill even with the new NEM rates.

I'm on NEM 2 so I'm good for the next 19 1/2 years or so... unless they manage to push through the fixed charges they are looking at, and the "equity" charges being looked at also. Not the fixed charges for per kW of solar, but income-based fixed charges. If that one ever goes through that is truly a time where I'll get my lazy butt of the couch and mobilize.

[SunEagle]

I have NE and NW panels in SoCal, normally that would be a bad idea and yes winter production sucks, but thanks to SDG&E somehow reaching this far north with their sky high pricing and the magic of NEM 2.0, the summer generation carries the year.

I have Powerwall Dashboard and Home Assistant running in VMs as well as an Emporia Vue Utility Connect, and I've downloaded and summed 4 PVWatts runs (SE, SW, NE, and NW) hourly data into Excel to compare with actuals, as well as Green Button data and CSV import from the Tesla app.

Last June 24th (day after PTO, first day after solstice that wasn't throttled) I was able to record a full day of production. My NE panels produced 2.50 kWh each, NW panels 2.80 kWh each, SE 2.71 kWh each, and SW 2.76 kWh each.

Now fast forward to Winter solstice, NE was 676 Wh each, NW 1.1 kWh each, SE was 1.54 kWh each, and SW was 1.07 kWh each.

Now one thing is my NW and SW panels are paralleled in a string. So while my SW production seems to be "brought down" my NW production seems to be "brought up."

And finally production from June 24th to Dec 24th looked like this: NE 254 kWh each, NW 326 kWh each, SE 350 kWh each, and SW 328 kWh each.

So while not completely North or South, my Northerly production was certainly worth it for me and I would still get those panels if I had to do it again. For my location, PVWatts puts North production at 69.5% of South production, with only azimuth changed. PVWatts has proven fairly accurate for my system so far.

I am glad those Northern panels are working for you. Most end up spending a lot more then that kind of panel can produce making the payback very long and hard. Hopefully you will reduce your electric bill even with the new NEM rates.

[OCJ]

The historical problem is that Northern facing panels in the North hemisphere will rarely produce a lot of power during the Winter months because the sun is too low in the sky.

If you are getting inflated output info then try to remember that if there is a low sun or clouds or smoke then most panels no matter what their tilt will not output anything close to their nameplate wattage let alone 68% and North facing panels fall into the category of low sunlight.

I have NE and NW panels in SoCal, normally that would be a bad idea and yes winter production sucks, but thanks to SDG&E somehow reaching this far north with their sky high pricing and the magic of NEM 2.0, the summer generation carries the year.

I have Powerwall Dashboard and Home Assistant running in VMs as well as an Emporia Vue Utility Connect, and I've downloaded and summed 4 PVWatts runs (SE, SW, NE, and NW) hourly data into Excel to compare with actuals, as well as Green Button data and CSV import from the Tesla app.

Last June 24th (day after PTO, first day after solstice that wasn't throttled) I was able to record a full day of production. My NE panels produced 2.50 kWh each, NW panels 2.80 kWh each, SE 2.71 kWh each, and SW 2.76 kWh each.

Now fast forward to Winter solstice, NE was 676 Wh each, NW 1.1 kWh each, SE was 1.54 kWh each, and SW was 1.07 kWh each.

Now one thing is my NW and SW panels are paralleled in a string. So while my SW production seems to be "brought down" my NW production seems to be "brought up."

And finally production from June 24th to Dec 24th looked like this: NE 254 kWh each, NW 326 kWh each, SE 350 kWh each, and SW 328 kWh each.

So while not completely North or South, my Northerly production was certainly worth it for me and I would still get those panels if I had to do it again. For my location, PVWatts puts North production at 69.5% of South production, with only azimuth changed. PVWatts has proven fairly accurate for my system so far.

[SunEagle]

Okay, going to make a couple SWAGS here. Since both of those companies are headquartered in California, you're in California, yes?

California has a thing called Net Metering (NEM) 2. It's about to end and be replaced with NEM 3, or whatever. You have until mid April for what's written below to apply.

I'm guessing since you're talking about tilt kits the "shady" side is the North side?

In Northern California, North facing panels can produce 68% of South facing panels annually. Normally, people in other states might not think that's worth it. Thanks to California IOUs absurdly high electricity rates and the magic of NEM 2, it actually is worth it. PROVIDING you don't pay an absurdly high amount for your panels and/or get absurdly high priced financing, and the shading you're referring to isn't actually trees or buildings.

The reason it still makes sense is in the summer, when the sun is higher in the sky due to the tilt of the Earth and its orbit around the sun, especially in late June, north facing panels will produce 98% of south facing panels, even parallel with your roof. During this time, those north facing panels will generate credits that you can then use later in the year.

That's right, NEM 2 treats production as an annual bucket. Put it in and take it out later. And what you put in goes in at full retail rate as a credit for use later.

Please do provide more information, and provide it quickly as the NEM 2 countdown is in effect. You have a short window of time to lock it in.

The historical problem is that Northern facing panels in the North hemisphere will rarely produce a lot of power during the Winter months because the sun is too low in the sky.

If you are getting inflated output info then try to remember that if there is a low sun or clouds or smoke then most panels no matter what their tilt will not output anything close to their nameplate wattage let alone 68% and North facing panels fall into the category of low sunlight.

[OCJ]

Okay, going to make a couple SWAGS here. Since both of those companies are headquartered in California, you're in California, yes?

California has a thing called Net Metering (NEM) 2. It's about to end and be replaced with NEM 3, or whatever. You have until mid April for what's written below to apply.

I'm guessing since you're talking about tilt kits the "shady" side is the North side?

In Northern California, North facing panels can produce 68% of South facing panels annually. Normally, people in other states might not think that's worth it. Thanks to California IOUs absurdly high electricity rates and the magic of NEM 2, it actually is worth it. PROVIDING you don't pay an absurdly high amount for your panels and/or get absurdly high priced financing, and the shading you're referring to isn't actually trees or buildings.

The reason it still makes sense is in the summer, when the sun is higher in the sky due to the tilt of the Earth and its orbit around the sun, especially in late June, north facing panels will produce 98% of south facing panels, even parallel with your roof. During this time, those north facing panels will generate credits that you can then use later in the year.

That's right, NEM 2 treats production as an annual bucket. Put it in and take it out later. And what you put in goes in at full retail rate as a credit for use later.

Please do provide more information, and provide it quickly as the NEM 2 countdown is in effect. You have a short window of time to lock it in.

[bcroe]

Something to consider. The tilt kit is to allow catching all the sunlight
heading for your roof, with the minimum number of panels. If you just
lay the panels flat, more will be required to catch all the sun, but they
will still get just as much energy. The tilt kit might allow catching some
sun that would have missed the roof entirely, but they have lots of
issues. Under clouds more panels will perform better, the more clouds,
the bigger the advantage. Bruce Roe

[J.P.M.]

1.) How may kWh/yr. do you use ?
2.) How many kWh/yr. is each proposal producing ?
3.) How big is each system in STC kW ?
4.) What are your roof orientations, tilt and azimuth ?
5.) What's your zip code ?
6.) Most residential PV systems offset a substantial portion of an annual electric bill, most of the time greater than 2/3 of the usage. Single digit % offsets are unusual. If I'm reading what you have written correctly, if shading is so much it reduces offsets to single digits %ages, PV is probably not going to be cost effective

I'd suggest you need to supply a lot more info before folks here can offer intelligent opinions on what vendors are providing.

[dreamypenguin]

They did tell me the kWh difference in numbers, too. One bid was ~370/month and the other was around 600 (with the both sides of the roof installation).

I tried to go use pvwatts but I am not that technical. It's too complicated for me to use properly, I think?