New Construction: Experience of getting new solar roof + powerwalls

[ScottFLA]

Hello all -

I just thought I'd post here to see if anyone else is going through the same experience I am. I own a 2020 MX, love the car and have confidence in Tesla. So, when it came time for my wife and I to design and build a custom waterfront home I first looked into the Tesla panels, but then as I learned more about the solar roof I decided to go with that since wife doesn't like the appearance of panels. Mind you, this decision was made before we broke ground so I'll be looking at some change orders that include a partial credit from my GC on the original shingle roof. We live in Florida so obviously solar makes a lot of sense.

Here are the specs of my system:
Your Order
7.84 kW Solar Roof
Estimated energy produced: 10,968 kWh /yr
2 Powerwalls

I am not well versed in construction, but thought I'd give some thoughts. First, obviously make this decision before your draftsman is done and the project is permitted if possible, although that part is not turning into a very big deal since the change was made before we broke ground and a roof is not structural.

Currently our house has the block stemwall and lower first floor done and framing has started for the main floor. GC thinks it should be ready for roof in December.

Here is where things gets a little dicey. Whereas in the Tesla car buying experience I liked the fact that all communication was via text, when you have a general contractor (GC) the benefit is he takes care of everything. However, since the Tesla roof is on my account all communication is through me, the owner, and it's a little bit of a challenge and would be nice if Tesla would tell you who the local sub will be so your GC can collaborate. All Tesla will tell you is that once the framing is done, that's when they decide on who is installing and that's when they do a site visit and apply for the roof permit.

Putting myself in my GC's place I can understand he is a little anxious, although he thinks the roof is a good idea. However, it makes it tough to collaborate and to make sure scheduling is on time when he has to go through me, and then I have to text Tesla, etc. My GC can't have framing done and then have the house exposed to weather damage. Anyway, the latest issue is Tesla is just saying my GC should use an underlayment when framing is done and they did email me a PDF with the recommended underlayment, etc. My GC can deal with that, but now I'm the middleman. It can make for a challenge.

Sorry for being so long-winded but has anyone done a solar ROOF on new residential construction? I guess my biggest fear is that the house is all framed out and Tesla says the solar shingles or PWs are on backorder, and then the whole project is held up which would not be cool.

If anyone is interested I'll continue to update, but also wanted to learn from others if anyone has been through this. Kind of feel like I'm flying by the seat of my pants here.

 

[BrettS]

I’m not sure how far along in this process you are or how you have analyzed your power usage and such, but to me a 7.84kW system with an annual production of 11,000kWh sounds very small for a house here in florida, especially if you have an electric car to charge. Given that the solar roof isn’t really very expandable once it’s in place I would strongly suggest that you seriously consider increasing the number of active tiles so you can produce 1.5 or 2 times as much power.

 

[getakey]

that is small. What is the sq feet of the house?

 

[mongo]

Hello all -

I just thought I'd post here to see if anyone else is going through the same experience I am. I own a 2020 MX, love the car and have confidence in Tesla. So, when it came time for my wife and I to design and build a custom waterfront home I first looked into the Tesla panels, but then as I learned more about the solar roof I decided to go with that since wife doesn't like the appearance of panels. Mind you, this decision was made before we broke ground so I'll be looking at some change orders that include a partial credit from my GC on the original shingle roof. We live in Florida so obviously solar makes a lot of sense.

Here are the specs of my system:
Your Order
7.84 kW Solar Roof
Estimated energy produced: 10,968 kWh /yr
2 Powerwalls

I am not well versed in construction, but thought I'd give some thoughts. First, obviously make this decision before your draftsman is done and the project is permitted if possible, although that part is not turning into a very big deal since the change was made before we broke ground and a roof is not structural.

Currently our house has the block stemwall and lower first floor done and framing has started for the main floor. GC thinks it should be ready for roof in December.

Here is where things gets a little dicey. Whereas in the Tesla car buying experience I liked the fact that all communication was via text, when you have a general contractor (GC) the benefit is he takes care of everything. However, since the Tesla roof is on my account all communication is through me, the owner, and it's a little bit of a challenge and would be nice if Tesla would tell you who the local sub will be so your GC can collaborate. All Tesla will tell you is that once the framing is done, that's when they decide on who is installing and that's when they do a site visit and apply for the roof permit.

Putting myself in my GC's place I can understand he is a little anxious, although he thinks the roof is a good idea. However, it makes it tough to collaborate and to make sure scheduling is on time when he has to go through me, and then I have to text Tesla, etc. My GC can't have framing done and then have the house exposed to weather damage. Anyway, the latest issue is Tesla is just saying my GC should use an underlayment when framing is done and they did email me a PDF with the recommended underlayment, etc. My GC can deal with that, but now I'm the middleman. It can make for a challenge.

Sorry for being so long-winded but has anyone done a solar ROOF on new residential construction? I guess my biggest fear is that the house is all framed out and Tesla says the solar shingles or PWs are on backorder, and then the whole project is held up which would not be cool.

If anyone is interested I'll continue to update, but also wanted to learn from others if anyone has been through this. Kind of feel like I'm flying by the seat of my pants here.

I can understand the stress with being in the middle. If it helps my understanding is the underlayment is all the peel and stick type, so once that is on (along with standard penetration flashing) your roof is weathertight.
Biggest thing I can think of settle ahead of time is integrating the conduit for the solar wiring.

 

[ScottFLA]

Thanks for the comments so far, and I welcome the input on the system itself. When I did the online analysis during the Tesla ordering process they recommended a little over twice the amount of solar. Going by memory I think around 17.5 kwh. I got cheap and scaled it back, which after tax credits made it go from around 72K to 52K. I am taking other measures to make the home as energy efficient as possible to include impact glass throughout, and even the block will be filled.

I am not locked into anything and my GC has other non-Tesla bids, one that produces 15 kWh and uses 36 Hanwha Q CELLS 315W. According to that company, that would cover 100% electric, but I doubt it has all the bells and whistles of the Tesla app and the AI. That system also comes with the SolarEdge SE10000H-US inverter. The cost is $51,000 but I also have to factor in that I'll then be paying the cost for the shingled roof, and with all those panels it'll look a little funny. Then again, maybe panels are a thing of beauty.

The home is 12' ceilings w/ 2500 sqft main living with the garage below the house, as well as an additional "uninsurable" 1000 sqft below that can be converted into a rec room or home theater. If a hurricane comes just carry everything upstairs. I'll use ductless AC below.

I though that with the dual PWs and the AI used by Tesla it would still offset most of my power bill by using the grid only during the cheapest rates, if at all. This all goes to the heart of my anxiety - there is no "Tesla Solar Store" where I can walk in and get a full seminar.

 

[getakey]

What is your Peak Time period. I doubt if you can make it through Peak completely on the 2 PWs using AC.

 

[BrettS]

I though that with the dual PWs and the AI used by Tesla it would still offset most of my power bill by using the grid only during the cheapest rates, if at all.

I touched on this in another post, but I’ll say it again here. The powerwalls won’t add any extra power to your system. And right now I don’t believe that any utility here in Florida offers time of use rates, so there is no need to time shift your power usage with the powerwalls. In the end your solar system will only produce so much power. If you’re using 20,000kWh annually and your solar system is producing 11,000kWh annually, then you’ll still need to buy 9,000kWh from your power company. Having powerwalls won’t change that. If you were in an area with TOU rates then the powerwalls could help to make sure that you purchase those 9,000kWh at the cheapest price, but like I said, I don’t believe that any utility in florida is offering TOU rates right now.

 

[BrettS]

Also, just to be clear, there’s nothing wrong with buying a smaller system that won’t offset 100% of your power bill. A lot of people do that. Like with my above example, if you are only buying 9000kWh per year your power bill will still be way less than if you were buying 20,000kWh. However, the reason that I’m suggesting that you seriously consider whether you want such a small system is because with the solar roof once you put it on you will be stuck with it. If you discover a year down the line that you wish that your system was twice as big it’s not like you can just add more panels like you could with a solar panel install. I don’t believe that tesla does ‘upgrades’ to the solar roof where they replace non active tiles with active ones on existing roofs.

 

[getakey]

Didn't realize there are not TOU rates in FL. Agree with everything Brett has stated

 

[ScottFLA]

I touched on this in another post, but I’ll say it again here. The powerwalls won’t add any extra power to your system. And right now I don’t believe that any utility here in Florida offers time of use rates, so there is no need to time shift your power usage with the powerwalls.

Thanks, I honestly had no idea. I have Duke Energy and just Googled it and you're right on, not offered in this area. More to think about....

 

[getakey]

What are the rates in Florida. Our PG&E rates are about the highest anywhere.
Peak is $.54/kWh
Partial Peak is $.27/kWh
Fortunately, I get an overnight EV rate of $.13/kWh

 

[cridinger82]

Fpl does offer tou rates. Tesla just told me about this yesterday. Haven't looked into it to much..

 

[BrettS]

Fpl does offer tou rates. Tesla just told me about this yesterday. Haven't looked into it to much..

That’s interesting. I think that’s reasonably new. I was with FPL for a while before I moved and at that time they didn’t offer any TOU rates. Of course I moved like 5 years ago, so I guess a lot might have changed since then. I’m with Duke now and they currently do not.

 

[cridinger82]

ya they started it recently. Tesla didn't know until a few customers down here told them that FPL did recently start TOU rates. They did not offer them as of the end of 2018 when i last checked solar out... but retail rates are fairly cheap for fpl and i really need to dig in an do calculations on tou rates. 1:1 netmetering with fpl is really killer by itself at the moment .

 

[BrettS]

I just took a look at their web site and this is their rate chart:

But I don’t understand this at all. It looks like it is saying that off peak usage is a negative cost, but I can’t imagine that they would pay you to use electricity off peak. Are they saying that off peak is that much less than on peak?

 

[getakey]

I don't understaand several things about that chart including the negative rate. It does say "Rider" Does that mean you add the rates together during On/Off peak?
They have <1000 kWh On Peak, but no >1000 kWh On Peak
Same for Off peak, but reversed
Then at far right they use "fuel" instead of energy.

 

[BrettS]

I don't understaand several things about that chart including the negative rate. It does say "Rider" Does that mean you add the rates together during On/Off peak?
They have <1000 kWh On Peak, but no >1000 kWh On Peak
Same for Off peak, but reversed
Then at far right they use "fuel" instead of energy.

There are a lot of confusing things about that chart, but I can explain some of it.

“Normal” Utility billing has one rate for the first 1000kWh each month and a slightly higher rate for the rest of the power used each month. So that’s where the <1000 kWH and >1000kWh parts come in. I believe that for the non TOU residential service those columns are for the rate for the first 1000kWh and then the rest of the power usage, and then for the TOU service those columns are for on peak and off peak. I think they just chose a very confusing way to show two different kinds of rates in the same columns.

As far as the fuel charge, florida utilities separate out a cost for the fuel they burn to make the electricity. So for the normal non TOU rate you would pay the total of all the columns. For the first 1000kWh you would pay the <1000kWh Energy charge + the Conservation, Capacity and environmental charges, plus the <1000kWh fuel charge. For the rest of the power you used you would pay the >1000kWh Energy charge + the Conservation, Capacity and environmental charges, plus the >1000kWh fuel charge.

You make a good point about the rider. Maybe for on peak you would pay the normal rate +all of those charges and for off peak you would pay the normal rate minus those charges.

It’s definitely an incredibly confusing way to present the data in any case.

 

[zecar]

What are the rates in Florida. Our PG&E rates are about the highest anywhere.
Peak is $.54/kWh
Partial Peak is $.27/kWh
Fortunately, I get an overnight EV rate of $.13/kWh

Brutal. In Chicago my August bill average cost was 8.1 cents/kWh for all electricity. Including some expensive AC late in the afternoon. Hourly pricing. Overnight EV charging is usually about 7 cents.

 

[jboy210]

There are a lot of confusing things about that chart, but I can explain some of it.

“Normal” Utility billing has one rate for the first 1000kWh each month and a slightly higher rate for the rest of the power used each month. So that’s where the <1000 kWH and >1000kWh parts come in. I believe that for the non TOU residential service those columns are for the rate for the first 1000kWh and then the rest of the power usage, and then for the TOU service those columns are for on peak and off peak. I think they just chose a very confusing way to show two different kinds of rates in the same columns.

As far as the fuel charge, florida utilities separate out a cost for the fuel they burn to make the electricity. So for the normal non TOU rate you would pay the total of all the columns. For the first 1000kWh you would pay the <1000kWh Energy charge + the Conservation, Capacity and environmental charges, plus the <1000kWh fuel charge. For the rest of the power you used you would pay the >1000kWh Energy charge + the Conservation, Capacity and environmental charges, plus the >1000kWh fuel charge.

You make a good point about the rider. Maybe for on peak you would pay the normal rate +all of those charges and for off peak you would pay the normal rate minus those charges.

It’s definitely an incredibly confusing way to present the data in any case.

Sounds like the tiered plans we used to have here. There were 3 or 4 tiers and the price per kWh went as your consumption increased and you moved up tiers. Now, most of those plans are being converted to Time of Use.

 

[Prof]

I touched on this in another post, but I’ll say it again here. The powerwalls won’t add any extra power to your system. And right now I don’t believe that any utility here in Florida offers time of use rates, so there is no need to time shift your power usage with the powerwalls. In the end your solar system will only produce so much power. If you’re using 20,000kWh annually and your solar system is producing 11,000kWh annually, then you’ll still need to buy 9,000kWh from your power company. Having powerwalls won’t change that. If you were in an area with TOU rates then the powerwalls could help to make sure that you purchase those 9,000kWh at the cheapest price, but like I said, I don’t believe that any utility in florida is offering TOU rates right now.

I just spoke with FPL as I bought a new model S. They do have TOU rates and the plan hours are different for summer and winter seasons. They told me that just charging a car wouldn't make economic sense for TOU rates. One woulld need to shift other activities as well so a powerwall might make sense for shifting usage times.