Have 48 panels, want to install (flat roof, SFH, SF CA)

[Ampster]

We are running into this issue… our HPWH doesn’t like recirculating the hot water… might be able to insulate our hot water return pipe to get past this.

[ATTACH]n429403[/ATTACH]

I used a temperature sensor on the return line on my recirc system to turn off the recirc before the warm water got to the cold inlet. As far as using an additional HPWH for the radiant I don't know if the typical setting of 80 degrees will be a problem initially. My friend actually had radiant wall radiators which ran at a higher temperature and he was using a different model. It may not be worth the effort since gas is still the most economical

[chuckledog]

We are running into this issue… our HPWH doesn’t like recirculating the hot water… might be able to insulate our hot water return pipe to get past this.

Heat+Pump+w-recirculation+1331.pdf

[Ampster]

Thanks for the update.
I have a friend in Southern California who has radiant heat and uses a separate HPWH for that, He only turns it on during late Fall through early Spring, As you know radiant does not take high temperature water.

[chuckledog]

Update on heat pump water heater -- we've been using a Rheem Performance Platinum 80gal for much of the year. This is using about 100kWh per month or about 1 MWh per year.

We're switching our clothes dryer to electric -- that'll also run about 1 MWh per year.
The rest of the house appliances & lights combined run about 2 MWh per year.
The EV (Nissan Leaf, base model) with our current driving patterns uses about 2 MWh per year.

So that's 6MWh per year total -- leaving about 12 MWh per year extra.
So, we're putting it into home heating. We ran an HVAC local calc. It's not quite enough to heat our home, even with a favorable TOU rate plan, but it's enough to heat the basement and part of the upstairs. We're installing an AWHP tied into a radiant slab. We'll keep our old forced-air gas furnace around for the rest of the upstairs, the cold nights, and the power outages. (We've opted to not look into battery backup / Powerwall type stuff). The house won't be "net zero" but it felt like too big of a bet to shoot for that. If we overshoot our energy budget on electric, it can get expensive quickly. Maybe next decade when AWHP tech is more mature -- or maybe by adding mini splits.

As of right now we're in the middle of a remodel, using electric space heaters to keep warm with half our walls missing. Slightly crazy but the family seems supportive (again SF only gets down to 40F in the winter, if we had "real" winters I would be hating life right about now). Our gas furnace has been shut off for a year and our gas bills are a tenth of what they used to be.

My better half points out that if we can get our usage down to tier 1 in electric and tier 1 in gas, we'll get charged lower rates from PG&E for both. So shifting some but not all of the energy load from gas to electric has been very practical. We used to dip into tier 3 for gas which gets quite expensive.

Anyways thanks again to this forum for all the invaluable advice, I hope the information in this thread is useful to others as well.

[chuckledog]

Updating this old thread with some numbers. The system is consistently generating 4+6+5+3 = 18 MWh per year. CleanPowerSF tells us we’ve earned $1000 or so in credits. As we go all electric from natural gas we will likely consume as much or maybe slightly more than we produce.

Thanks again to this forum for all the guidance!

891B5B03-1594-48DD-B1D8-E7DC5830ECDF.jpeg

[J.P.M.]

Update on this old thread.

- Solar production has been 30% above PVwatts estimate/model but this is leveling out to 20%. Not sure why it under counted. I was told these are really good panels, it might be that, or the unusually dry season.
Happy to provide more details!

Could be several contributing reasons. Two of the more likely culprits might be:

1.) The input to PVWatts is not representative of the site conditions.
2.) The 6 months prior weather you've experienced may have been more conducive to PV generation than the weather data PVWatts uses for the same period.

The model help/info screens will tell you that even with input that's close to the actual array design parameters, yearly actual output might vary +/- 10 % or so from what the model pukes out.

Monthly output variance is maybe +/- 30 %.
6 months of output might be somewhere between the two.

My money would be about 2/3 of the diff. due to model input that's different from what's on your roof and the rest due to weather variation.

FWIW, data on running totals and ratios of actual vs. what the PVWatts model gives for my array from 10/17/2013 onward:

Using running 31 day totals:

Running 31 day actual total output/running 31 day PVWatts modeled total output:
Average: 0.9980
Minimum: 0.6426
Maximum: 1.3023
Std. Deviation: 0.0996
N =2,304

Using running 183 day totals:

Running 183 day actual total output/running 183 day PVWatts modeled output:
Average: 0.9824
Minimum: 0.8943
Maximum: 1.0756
Std. Deviation: 0.037
N = 2,121

Using 365 day totals:

Running 365 day actual total output/running 365 day PVWatts modeled total output:
Average: 0.9960
Minimum: 0.9575
Maximum: 1.0530
Std. Deviation: 0.0221
N = 1939

Data is from my array and deemed accurate but not guaranteed.
Your array results, output and actual vs. modeled output will be different.
I offer the above for information purposes only.

My climate has less summer/winter variation than most others with respect to irradiance. My thinking is that lower variation may help explain the lower 183 and 365 day variation in the PVWatts output vs. actual.

[Ampster]

Thanks again for the update. My CCA, Sonoma Clean Power, just offered incentives for installing a HPWH. In that process I also discovered additional rebates. I know Clean Power SF is still rolling out across the City but hopefully they will offer similar incentives in the future.
Hopefully, you got through the Public Safety Power Shutdowns late last year?

[chuckledog]

Update on this old thread.
- Everything has been working well.
- No issues during a recent wind storm.
- Solar production has been 30% above PVwatts estimate/model but this is leveling out to 20%. Not sure why it under counted. I was told these are really good panels, it might be that, or the unusually dry season.
- One roof leak from an improperly sealed drain. Interestingly, to dry out the affected interior room, we used alot of electric heat for 10 days. Our electric consumption was net positive during this time.
- Otherwise we are net positive for electric production just about every day. We will slowly switch our appliances over to electric as they wear out.

Thanks to everyone on this forum for all the invaluable advice.
- One piece of helpful advice was to use one company for both roofing and solar to reduce finger pointing when something goes wrong. I've learned alot about roofing over the past 6 months!
- Likely the best advice I got was to tilt the panels. The fact they are self-cleaning is really nice.

Happy to provide more details!

[Ampster]

I am glad it met your expectations. At that rate you will cover your consumption in less than ten days. Thanks for keeping us informed about the progress of your build.

[chuckledog]

First day of production. Partly foggy in the am otherwise clear. 58 kWh. PVWatts predicted 64 kWh so it's not far off.
10B50F66-96BB-4034-B786-E7732AFBFD30.jpeg

[chuckledog]

Panels were installed:
0248B4E6-26EA-44A9-9A8F-E76837BBD09D.jpeg

Pg&e took awhile to issue our permission to operate, but it finally came through.

The system just went operational!

Thanks again everyone on the forum here who who helped with advice and encouragement.

[ButchDeal]

Thanks! Pretty sure it's Ironridge XR100.

Question to the forum -- our inverter is a SolarEdge HD10000, and of course I'm very interested to be able to see the monitoring app(s), is there anything I should ask our installer in terms of networking or passwords to access the monitoring system?

It would be an SE10000h not HD10000

you want to ask for full access and owner
if you have good internet you want them to use the ethernet connection or third party wireless adapter, not cellular GSM

[chuckledog]

Thanks! Pretty sure it's Ironridge XR100.

Question to the forum -- our inverter is a SolarEdge HD10000, and of course I'm very interested to be able to see the monitoring app(s), is there anything I should ask our installer in terms of networking or passwords to access the monitoring system?

[khanh dam]

LOOKS GOOD! who manufacturer's that racking system? looks very tall to me!

[Ampster]

They're going with a 10 degree tilt.

Looks good. Thanks for the updates. I will be interested to see the production curve after a few days. Now you have the joys of wading through the TOU rate plans unless we hashed that out earlier.