Solar Roof layout

[Brennerman]

Tesla has started designing a system for my house.

currently there are two trees blocking the sun on the west side I am looking at trimming or removing. While I would like this to be near 7 kWh with three Powerwalls. I am wondering if I don’t need that much. Would I be fine with a 5 kWh system with three or two Powerwalls?

No EVs as of yet, plan on adding a cybertruck tri motor and our average usage is between 15 to 20kw per day.

 

[Ampster]

I am a big fan of over paneling. It is a good hedge against future price increases. Whether you need 2 or 3 PowerWalls depend on your goals, your rate structure, your consumption patterns and your sensitivity to power outages. I have a small hybrid inverter for backup and load shifting. I also have two Teslas but don't expect my backup inverter to charge my Teslas. AC coupling my Grid Tie system should enable me to charge during the day when I do have a power outage..

 

[Odiemac]

How’s the net metering rules where you live?

I agree with @Ampster, it’s a lot easier to over-panel at first then to add later. 5kw looks like it would cover about 50% of your pre-Cybertruck usage, so maybe only 30% with the Cybertruck. I concur about 2 powerwalls and more solar if you need to make a trade-off, it’s much easier to add Powerwalls later.

 

[Brennerman]

What I have gathered net metering is available not sure on specifics.

 

[jjrandorin]

Does the cost of a solar roof pencil out with that relatively small amount of production? OP just as it relates to power usage. You mention you dont have an EV.

My house usage is between 20-25 kWh a day, without my model 3 (3300 sq ft home, in an inland area). My daily commute is 80 miles round trip to work . I have a model 3 Performance, which I am sure will be more efficient than the cybertruck as far as wh/mi. My car uses almost exactly the same amount of power for my round trip commute (22-25 kWh) as my house does for the day.

My point is, depending on how much you drive your proposed electric vehicle, you would expect to double your electric usage. My model 3 still costs me like 1/3 the price on my daily commute for " fuel", and I have a 8.7 kWh sized solar install. If it were me, I would be trying to get as close to 100% of my yearly usage as I could, but this obviously depends on how your home sits etc. That system seems very small to me for what it likely costs though....

 

[brucet999]

View attachment 506654 View attachment 506654 View attachment 506654 Tesla has started designing a system for my house.

currently there are two trees blocking the sun on the west side I am looking at trimming or removing. While I would like this to be near 7 kWh with three Powerwalls. I am wondering if I don’t need that much. Would I be fine with a 5 kWh system with three or two Powerwalls?

No EVs as of yet, plan on adding a cybertruck tri motor and our average usage is between 15 to 20kw per day.

Your proposed plan does not indicate compass points. Where is south? Productivity is best on south-facing arrays tilted 20º or more; next best are west-facing about 10% less than south; then east.

If one of those arrays is east facing, you need to consider whether your local climate tends to morning fog, which would greatly reduce productivity.

If your PoCo allows net metering and a time of use rate structure, then a west-facing array will produce nearly as much power as south, but will hit its highest production during peak TOU rates, so might yield better economic return than south-facing.

Why do you need all of those power walls? Is your area prone to frequent and lengthy power outages? Are you trying to get off the Grid? Does your PoCo allow time-shifting so you can take power at night and deliver it to the Grid during peak rates time?

My experience with my local Tesla Energy/Solar City was poor response and stupid system design featuring an east-facing array in an area where the marine layer causes morning overcast during about half the year.

 

[Brennerman]

I don’t have final numbers to this project as of yet. Just trying to speculate about what I should be trying to get setup. I would like to be off the grid as possible so originally I thought I would need three for the future addition of an EV as well.


the house is south east facing

 

[brucet999]

I don’t have final numbers to this project as of yet. Just trying to speculate about what I should be trying to get setup. I would like to be off the grid as possible so originally I thought I would need three for the future addition of an EV as well.


the house is south east facing

There is no such thing as "off Grid as possible." You either are, or are not, connected to the Grid. If you are connected, the local PoCo dictates the terms of how you can use your system. You need to know what those rules are.

So Tesla proposes most of your solar tiles (the 2.7 kW array) facing northeast, the next-to-worst direction for solar in North America (only due north is worse). Do you often have morning overcast or fog? Both of those make easterly facing less efficient.
Why isn't the southwest-facing (1.6kW) array expanded? That is the best direction you have. Is the back half shaded by trees?
Why is there nothing on the other southeast-facing roof? Is that roof shaded?

Equipment location section says, "At time of installation the Tesla crew will discuss with you the exact location based on your preference and install feasibility" That is insane. You don't want to be making such decisions while a crew is standing around waiting to start. Exact locations of PV tiles should be settled before you sign the deal.

Check out your proposed systems using PV Watts. This free calculator is capable of adjusting solar inputs for latitude, longitude, compass direction and roof slope.
PVWatts Calculator

Enter the relevant information for your address, azimuth (compass direction expressed in degrees), roof slope, etc. for each of the proposed roof sections. If Tesla refuses to tell you the rated output watts of each tile, you can calculate it by dividing the proposed areas by the number of tiles.

 

[cwerdna]

While I would like this to be near 7 kWh with three Powerwalls. I am wondering if I don’t need that much. Would I be fine with a 5 kWh system with three or two Powerwalls?

No EVs as of yet, plan on adding a cybertruck tri motor and our average usage is between 15 to 20kw per day.

You've got your units mixed up. Solar system sizes are measured in kW. kW is a unit of power.

Your electricity usage in a day is measured in kWh, a unit of energy. Ditto for battery capacity.

See Extended Warranty opinions ... - My Nissan Leaf Forum.

Notice the screenshots you attached have the right units? Look at your electricity bill, as well. You'll see your energy charge is in a per kWh basis.

 

[Brennerman]

There are two trees blocking the sun. I am going to have those trimmed or removed to open up that side.

This is not the final. I just received a call the other day stating they are designing the system for my house. When I checked my account I saw this layout. I am hoping to open up another 2kw on the roof.

 

[brucet999]

There are two trees blocking the sun. I am going to have those trimmed or removed to open up that side.

This is not the final. I just received a call the other day stating they are designing the system for my house. When I checked my account I saw this layout. I am hoping to open up another 2kw on the roof.

Has someone done a shade survey noting what areas are covered hour-to-hour in both summer and winter? My SunPower dealer did that for me, but my experience with Tesla/Solar City was that no such efforts were made. Maybe they are better in your area, but you cannot afford to assume so.

What will the esthetic/garden comfort effect be from removing those shade trees? Are they deciduous, and therefor not a problem in winter?

 

[gnumeric]

I would recommend just adding the additional panels now to save yourself the headache later. I have almost the exact specs of your system (5.04 kW solar, 3 PW) and I wish I would have gotten more panels. Like you, I thought about getting a bigger sized system but I opted not to. Don't make the same mistake as me. Now I have to go through the headache of adding a second system.

You should know that Tesla won't add a second system until at least a year has passed since your original system has been in use. So a second system of extra panels probably won't qualify for the ITC tax credit before it drops to 0% in 2022.

 

[Brennerman]

No one has done a shade survey yet, he is an image from google showing the shaded area.


Thanks Gnumeric, I will follow that advice!

 

[jboy210]

With our install they they gave us a couple of option for the roof. Did they do that for you? We got a 9KW and 12KW option and went with the 12KW option.

The 9KW option would have worked, since that is what the traditional solar panel systems we were looking at produced. But, since this is a solarglass roof adding additional solar, means re-roofing. So we went with the max 12KW option.

 

[Brennerman]

Not yet, I am waiting for a call back to discuss the system they are designing. I was looking at my account and had seen this layout in there. There is nothing final as of yet.

 

[Brennerman]

Moving along, they have updated the system (with removing the trees block the left side of the house).

this is what I was hoping to have so I am excited this is coming together!

 

[Dan123]

Moving along, they have updated the system (with removing the trees block the left side of the house).

this is what I was hoping to have so I am excited this is coming together!

It seems like this is the best you can do with your roof, which is not ideal.

If you want to have full-house backup, you need at least 2 PWs. If you want just to shift loads between peak and off-peak, you can probably just get one PW.

 

[Brennerman]

It may not be ideal, but this should cover my needs and then some. I am planning on having this as a house backup with the intention of adding an EV in the near future, so I was thinking 3 Pws would be sufficient.