New solar install

[poorpilot]

Hi there,
I’m new to the solar game and I was all excited about my new system but after scouring thru this forum I’m worried to the point of canceling my contract with Tesla. I’m in Phoenix and looking at the 7.53 system with 2 PW. I have to have a system that faces East and west due to historic home guidelines. Tesla has quoted me about 33K for everything and that is using the Hanwha panels and delta inverters. They are estimating a yearly production of 12400. My total usage last year was about 15Kwh. So my question is how does this stack up? Are these panels good or not? Will they work well in the Phoenix heat? Or any other insights? Thanks

 

[poorpilot]

15,000 kWh of usage last year

 

[Dan123]

There is nothing wrong with the panels or delta inverter. It is not the best available, but pretty good.

Is there a way to fight those historic guidelines?

33k for 7.5 system and 2 PWs seems reasonable, even on the cheap side. Is that after the tax credit?

Tesla estimate of solar production seems reasonable, but it depends on the exact orientation of your home, and the slope of the rood, and shading conditions (if any).

 

[poorpilot]

No there isn’t. Plus it would look pretty awful as well due to the shape of the house. This is the price breakdown:

 

[poorpilot]

My biggest concern is under normal conditions is the system large enough to charge the Powerwall during the day if fully discharged. And say during a power outage can they run my AC unit, which is a 5 ton package unit. And are the panels efficient in the summer heat

 

[dhrivnak]

No there isn’t. Plus it would look pretty awful as well due to the shape of the house. This is the price breakdown: View attachment 504473

We install solar and yes that sounds like a fair price and a reasonable production estimate

 

[jjrandorin]

My biggest concern is under normal conditions is the system large enough to charge the Powerwall during the day if fully discharged. And say during a power outage can they run my AC unit, which is a 5 ton package unit. And are the panels efficient in the summer heat

Since solar production varies during the year, I would imagine that for at least 7-8 months a year you would have enough power. Someone else linked this in another thread, but this is tesla's guidance on how to calculate how much power you can reasonably expect from your system:

Solar Panels Monitoring | Tesla Support


Here is the relevant part, if you dont want to click the link:

======================================

How can I ensure my system is working well?
System performance is measured in how many kilowatt-hours (kWh) it produces over a given period of time. A simple way to tell if the system is performing as expected is to utilize the “Daily kWh Rule-Of-Thumb” method below:

1. DC SYSTEM SIZE: Gather your DC (direct current) system size from your system designs or under "System Description" on your contract.
2. SEASONALITY FACTOR: Systems perform differently based on the time of year and so the production estimate will vary throughout the year. Seasonality Factors are based on the knowledge that the longest day of the year is June 21st and the shortest December 21st. Use the Seasonality Factor listed below:
   • Summer
     • May- June-July: 5 to 7
   • Fall/Spring
     • August-September-October/February-March-April: 3 to 5
   • Winter
     • November-December- January: 1 to 3
3. CALCULATE ENERGY PRODUCTION ESTIMATE: Estimated daily kWh system production= DC System Size X Seasonality Factor
4. ACTUAL ENERGY PRODUCTION: In your Tesla app, review the actual daily solar energy production for a recent full day. It's best to use a day where the cloud cover percentage is near zero.
5. ANALYZE: Compare the estimate you calculated to the production. If the production is equal to or greater than the estimate, then the system is performing as expected. If the production is less than the estimated, look to see whether shading or weather are a factor and if the low performance is consistent from day to day. In winter, performance for some systems may be near zero due to a combination of shading and weather.

Example: You have a 6 kW (DC) solar system. The estimated daily production for your system by season would be:

• Summer (May, Jun, Jul): 30-42 kWh/day
• Fall (Aug, Sep, Oct) or Spring (Feb, Mar, Apr): 18-30 kWh/day
• Winter (Nov, Dec, Jan): 6–18 kWh/day

On June 3rd, the system produced 38 kWh. This is in line with the estimated daily production range for June (30-42 kWh/day). Based on this, the system is performing within expectations.
=============================================

So, in your case, System Size (DC) =7.5. During the winter (nov, dec, jan) when production is lowest you will likely see between 7.5 and 22.5 kWh a day. Whether this is enough for you depends on what mode you are running the powerwalls in. You will likely be on a TOU plan, so you really only need the powerwalls to power your home during that TOU period, rather than if you were attempting to be "self powered" and use almost no grid power. As you move through January toward February, the daily power on sunny days will gradually increase.

For spring, you will see between 22.5 and 37.7 per day. Into summer, 37.5 - 52. Of course, during the summer you will be using your AC so your daily usage will also be much higher than spring. The system will not generate the same amount of power every day, and you should also know that AC is a huge electrical draw, so in a power outage situation you would want your AC backed up, but you would NOT be running it all day if you had no power. You might be turning it on for 30 minutes at a time for various times just to make your home "livable" but you will not be running your AC on powerwalls with no grid power all day.

The pricing looks good, especially for solar and 2 powerwalls. You could see if there are other panels available for an upcharge if you dont like those. If it were me, I would make sure they are putting as many panels as possible on the roof portions I am allowed to put them on, and I would see if I could get the best panels they offered as far as power output, since you can not put them on the most efficient roof plane.

It was my experience in 2015 that the original quotes was always something like 80-85% of your yearly usage, and I had to push to get a larger system by telling them I was getting an EV (expecting significant increase in electricity usage). Utilties do not want to authorize interconnect agreements when you are a net producer instead of net consumer, so solar companies size the systems to fit in those guidelines.

There is usually an exception form you can fill out stating that you expect increased usage in the next 12 months (installing a pool, buying an EV, etc).

Anyway, as a reference point, my system is 8.7 and I am generating about 25-27 Kwh a day right now, near the end of of January. If I were you, I wouldnt cancel, but I would push back and try to get as close to 100% of my current usage as I could, possibly by paying more for upgraded panels etc. People almost always use more power when they get solar, because they say "I have solar, I can do XXX".

Good luck

 

[Dan123]

My biggest concern is under normal conditions is the system large enough to charge the Powerwall during the day if fully discharged. And say during a power outage can they run my AC unit, which is a 5 ton package unit. And are the panels efficient in the summer heat

I think you are getting a very good deal.

Do you have space for more panels? If so, put more panels. If not, then this is the best you can do.

Hanwha have a good temperature coefficient. They are fine for heat.

As far as running the 5-ton AC, that depends on what kind of AC it is. It may be possible if the AC compressor has a low LRA value (on the sticker of the compressor outside). Should be below 58 for 2PWs. If it is higher, you may be able to install a soft-start device (Tesla should tell you if it is possible or not).

As far as sufficiency to recharge - if it is a sunny day, yes, it will be more than sufficient to recharge the batteries.

P.S. I would make sure that they do not undersize your inverter too much. They should install at least a 7kw inverter.

 

[poorpilot]

Thanks for the replies. So I talk to Tesla today and am finding them rather rigid. They only will do the hanwa panels now, they only increase systems increments of 12 and the contract is rather vague not stating what types of equipment is to be used. My roof has room for a few more panels but certainly not 12. I have a few other quotes for systems that are a bit larger using Panasonic panels both either in all black or black with the white grid lines. The black with white have a higher wattage than the all black (330 vs 325). I’m gonna post the other quotes as now I’m debating, do I go with the slightly larger system with no power walls or the Tesla/hanwa panels and power walls. The one thing that has me a bit is the 12 year warranty on the hanwa panels. I’m financing the system and while most likely I will pay it off faster than the 20 years, do I want to be making payments on something that isn’t under warranty any more. As most of you have already gone thru this process, any insight would be great. I have APS in AZ and TOU plan.

 

[poorpilot]

 

[solarAddict]

I'm new to the solar too (but was eyeing long before Tesla) and I got quotes from energysage as well. These quotes were all over the place - prices, production numbers, equipment etc. So I polled my work office, got 4 references and setup a meeting with all of them. Get someone local to look at your particular situation. Even if you don't go with them, it will help you to understand the details of your setup.

Good luck.

 

[jjrandorin]

Thanks for the replies. So I talk to Tesla today and am finding them rather rigid. They only will do the hanwa panels now, they only increase systems increments of 12 and the contract is rather vague not stating what types of equipment is to be used. My roof has room for a few more panels but certainly not 12. I have a few other quotes for systems that are a bit larger using Panasonic panels both either in all black or black with the white grid lines. The black with white have a higher wattage than the all black (330 vs 325). I’m gonna post the other quotes as now I’m debating, do I go with the slightly larger system with no power walls or the Tesla/hanwa panels and power walls. The one thing that has me a bit is the 12 year warranty on the hanwa panels. I’m financing the system and while most likely I will pay it off faster than the 20 years, do I want to be making payments on something that isn’t under warranty any more. As most of you have already gone thru this process, any insight would be great. I have APS in AZ and TOU plan.

Why cant you go with the larger system and add the powerwalls? Do the people you are getting quotes from not do powerwalls as well? I have only had my powerwalls for 2-3 weeks now (had solar since 2015) and cant imagine having solar without the powerwalls now, if I was buying new.

 

[Dan123]

Thanks for the replies. So I talk to Tesla today and am finding them rather rigid. They only will do the hanwa panels now, they only increase systems increments of 12 and the contract is rather vague not stating what types of equipment is to be used. My roof has room for a few more panels but certainly not 12. I have a few other quotes for systems that are a bit larger using Panasonic panels both either in all black or black with the white grid lines. The black with white have a higher wattage than the all black (330 vs 325). I’m gonna post the other quotes as now I’m debating, do I go with the slightly larger system with no power walls or the Tesla/hanwa panels and power walls. The one thing that has me a bit is the 12 year warranty on the hanwa panels. I’m financing the system and while most likely I will pay it off faster than the 20 years, do I want to be making payments on something that isn’t under warranty any more. As most of you have already gone thru this process, any insight would be great. I have APS in AZ and TOU plan.

If aesthetics is not an issue, black panels are less efficient. I don't think solar panel warranty length is that important. First, they are things that are unlikely to fail in your system. Second, if a panel fails after 12 years, the panels themselves are not that expensive $200 now, and probably even cheaper in 12 years.

 

[Dan123]

You can also join a solar co-op
Co-ops – Solar United Neighbors

 

[JayClark]

My biggest concern is under normal conditions is the system large enough to charge the Powerwall during the day if fully discharged. And say during a power outage can they run my AC unit, which is a 5 ton package unit. And are the panels efficient in the summer heat

I live in the southeast valley outside of Phoenix, and I'll describe how I make it work for my system, and cut my SRP electric bill from around $3000/yr, to around 800/yr. Sorry this is so long, but I tried to state it in simple terms without complex calculations (which I actually did originally when sizing my system). I haven't made it a full year back around to peak summer with my system, but I did test my solar/PW setup during 4 days of about 107-109deg weather before it cooled down, and my calculations were holding solid. So here is my setup...

I have 4.0kW Solar, and 4 PWs. South Facing - but ultimately the direction doesn't matter when you have PWs, you just need to have a good estimate of your low winter production average, and high summer production averages. Surprisingly for me, my payoff was faster at this configuration (little solar, lots of PW - for my home size here in Arizona, and based on the most aggressive SRP rate plan)... than any other configuration with more solar and less PWs.

I give you this information, for comparison to your own homes usage. Ultimately, to make sense of what will work based on your specific Utility (APS, SRP, other?) rate plans in the valley, your home size, etc... you will need to know how much power your house "MUST" use during your utility peak periods for you to live acceptably comfortable. SRP lets me see my hourly usage for any given day in my online account.

My Size and High Level Power usage assessment:

• My house, at all times, uses as baseline of about 18-20kWrs (about 600-800 watts per hour for a 3600sqr foot house) no matter what, based on observing my SRP online hourly usage when I've turned everything off but absolute essentials. 2 refrigerators, small wine fridge, wifi, routers, 3 wifi APs, NAS server 24/7 a various home automation devices (hue hub, Smarthings hub, smart thermostats, etc), and clocks and such on various devices (oven, microwave, etc).
• plus about 15kWhrs of electric car charging each day on our chevy volt (Model Y soon to come!)
• We have 3 ac units, 4.5 ton, 3 ton, and 2 ton. The 4.5 and 3 tons AC units have to run a lot in the summer.

Power Usage of My Home during Peak periods:
In winter my house can sip as little at 20-24kWhrs for a whole day if we don't drive/charge out electric cars, and as little as 4kWhrs total during winter utility designated peaks-periods (higher rates), again during the winter, because we watch TV, cook, etc.

In the summer, the house can use as much as 150kWhrs per day when the heat is hitting 115 degrees and we make a couple 30-40 mile trips in our electric car and then charge them - also this peak is usually when low temps aren't going below 100 degrees overnight. The two bigger AC units are a must during the summer and I'm on SRP's solar plan, so peak window is between 2-8 in the summer, and I need the AC during those hours as both my wife and I usually are working from home. We do all car charging during off peak, so my main goal is to completely zero out all of my home peak usage, while still using reasonable AC during peaks.

AC is my key constraint for eliminating Peak-period AC usage which is my primary goal for saving money, and minimizing my electric bill. If I can eliminate my peak usage, ALL POWER usage is only charged at off-peak, and on SRP our solar plan off-peaks kWh rate charges are between 1/2 to as much as 1/3 the price of any other hourly rate plan (so like only 3.6cents off-peak per kWhr, vs about 7.5-45cents per kWh on all other plans). After measuring and checking my SRP usage, I need enough PW to eliminate my 18-24 (max) kWhr usage needs (with AC) during the summer peak periods.

So with that peak usage in mind, I also wanted about 25% slack, so that means my PWs needed to be at least 30kWhrs of storage. So that's 3 PWs, and I probably could have made this work for my home just fine. However, in addition to eliminating all peak power usage, I ALSO did want some "backup" capacity peace of mind. So in addition to powering my home, I added a fourth Powerwall to both give me some Backup capacity, but also that gives me even more slack if during the worst summer months we also have our annual monsoons that make it cloud for several days in a row. So, 4 Powerwalls, but only 4k of solar.

Financials:

So just by zeroing out my peak usage with the PWs (every single day), I've cut my electric bill at minimum of 50%, so in half - EVEN if I used the same amount of power as before I was on the solar generation rate plan, but just by shifting it off peak via the Powerwalls and having super cheap off-peak rates now on the solar plan. In reality, in addition to those savings, I'm ALSO using about 18-22kWhrs less per day with my small 4kWhrs PV system.

So, bottom line, for me to maximize savings and payback, I need just enough Powerwall (maybe plus a little slack for cloudy days, lets say 20% slack over my calculated needs for the worst peak period usage) capacity to cover my max summer peak-period usage. Then, I need just enough solar to to cover replenish the PWs each day. In my case, in the worst of the summer heat I actually have slightly less Solar than I need, but because I built in "slack" in the PW capacity (by getting 4 Powerwalls) I can finish "re-charging" the Powerwalls on the weekend. The reality is this is only going to be needed during the worse 8 weeks of the summer. Right now in the winter, I only need about 25-35% of the capacity of the 4-PWs but that allows be to extend the life by only running the Powerwalls in the 30-60% charge range, until I need the full range as summer heat ramps up.

If you calculate using less than the

Bottom line savings:

• Winter Low billing months before I had solar/PW=~$90-120; After Solar/Powerwall monthly billing=$45-60
• Summer High billing months before I had solar/PW=~$400-475; With Solar/Powerwall monthly billing=$125-175

Hope some of this is useful for comparing to your situation.

 

[Tedslaract]

No there isn’t. Plus it would look pretty awful as well due to the shape of the house. This is the price breakdown: View attachment 504473

YIKES!....crazy price difference... I got quoted 2k less for the same size system...but for only 1 power wall.....glad I didn't pull the trigger.