Solar + Powerwall install questions

[07stuntar1]

Solar City came over to my house to estimate on Solar Panels + Power Wall. Without looking at my power bill they estimated 2 systems 7.5 kWh and 3 power walls. I’m was a bit confused why it’s 2 and 3 and not 3 systems 3 powerwalls. I asked why and he said someone requested 3... Not sure who. There’s not much communication with them besides email.
After digging in and looking at my power bill I use about 35 kWh.


I had a few questions:

How many Solar Panel are per systems?

I asked and he said it only made to off set my bill 90%. Not sure why I wouldn’t want to do 100% ?

I saw the PW2 max output was 7kWh so does 2 mean 14kWh and 3 is 21kWh. Is that enough for a house. My car charges at 7kWh. Sounds like it is wired in series will this give me maximum battery length to last the whole night?

Most people I talk to say micro inverters per panel are better because one weak panel doesn’t bring down the power. If one inverter breaks the rest of the panels still work. Also easier to upsize later. Solar City quoted and said Solar Edge with power optimizers are better. Any input on this?

He said they are not Tesla Panels but 315W Q-Cells. Anyway to get the Tesla Panasonic 330W or 325W?

 

[jakestgermain]

Solar City came over to my house to estimate on Solar Panels + Power Wall. Without looking at my power bill they estimated 2 systems 7.5 kWh and 3 power walls. I’m was a bit confused why it’s 2 and 3 and not 3 systems 3 powerwalls. I asked why and he said someone requested 3... Not sure who. There’s not much communication with them besides email.
After digging in and looking at my power bill I use about 35 kWh.


I had a few questions:

How many Solar Panel are per systems?

I asked and he said it only made to off set my bill 90%. Not sure why I wouldn’t want to do 100% ?

I saw the PW2 max output was 7kWh so does 2 mean 14kWh and 3 is 21kWh. Is that enough for a house. My car charges at 7kWh. Sounds like it is wired in series will this give me maximum battery length to last the whole night?

Most people I talk to say micro inverters per panel are better because one weak panel doesn’t bring down the power. If one inverter breaks the rest of the panels still work. Also easier to upsize later. Solar City quoted and said Solar Edge with power optimizers are better. Any input on this?

He said they are not Tesla Panels but 315W Q-Cells. Anyway to get the Tesla Panasonic 330W or 325W?

 

[jakestgermain]

Where are you located? I just had Tesla install Panasonic SC 330 panels at my home. I basically told them I didn't want the Q-Cells and they gave me the 330's

 

[L-P-G]

• 90% vs 100% - Probably because Tesla Energy is in the business of repeatable installs to do as many as possible and as quickly as possible, I'm guessing to do 100% of your consumption it wouldn't be divisible by 7kW (which is what their tiers are). This would mean customizing the plans which they probably don't want to do since it would increase the engineering hours
• This is a common occurrence with TE, they just quote you enough PWs to take the full 100% output of your solar without taking into consideration curtailing of the frequency can modify the output percentage so you can have less PW than your solar produces. In other words you array can output 14k gallons per hour (in a perfect day without heat or cable losses) and the PWs can absorb 11kgal/h (14kgal/h) because their inverter (or keeping with the analogy) water pump can only handle that much. Your tank size would be 28k gal. Don't confuse the capacity of output with the capacity of storage. To know if that's enough you'd have to add up the loads you plan on running overnight and one, make sure you don't use more than 14kW/h and two, your added up loads don't use up more than you have stored.
• SolarEdge uses power optimizers which do the same thing as micro inverters, the main difference is that micros output AC and optimizers output DC

 

[Cirrus MS100D]

I just signed a contract last week for a more modest PV (4kW) system and 2 Powerwalls because they're important to us for backup purposes as we often lose grid power.

I did ask Tesla about using our HPWC, which is on a 60 amp circuit, and engineering confirmed that 1x Powerwall will accept "up to" a 30 amp circuit (sounds like this is what you have?), 2x Powerwall will accept "up to" a 60 amp circuit (which is what we have), so we're planning on hanging our 60 amp HPWC off of the 2x Powerwalls. (In another thread, I brought up the question about Powerwall sizing + HPWC and went into more detail about our setup, which is a detached garage/outbuilding, not connected to our main house.)

Obviously there are other factors to take into account for various items like starting requirements vs. running requirements (well pumps, HVAC, etc.) but you generally have the gist of them being additive, though understand that 7kW is the peak (initial) draw for 10 sec for a single Powerwall, with 5kW being continuous. So, yes, stringing 3x together you should be able to output 15kW continuous.

 

[Dan123]

Solar City came over to my house to estimate on Solar Panels + Power Wall. Without looking at my power bill they estimated 2 systems 7.5 kWh and 3 power walls. I’m was a bit confused why it’s 2 and 3 and not 3 systems 3 powerwalls. I asked why and he said someone requested 3... Not sure who. There’s not much communication with them besides email.
After digging in and looking at my power bill I use about 35 kWh.


I had a few questions:

How many Solar Panel are per systems?

I asked and he said it only made to off set my bill 90%. Not sure why I wouldn’t want to do 100% ?

I saw the PW2 max output was 7kWh so does 2 mean 14kWh and 3 is 21kWh. Is that enough for a house. My car charges at 7kWh. Sounds like it is wired in series will this give me maximum battery length to last the whole night?

Most people I talk to say micro inverters per panel are better because one weak panel doesn’t bring down the power. If one inverter breaks the rest of the panels still work. Also easier to upsize later. Solar City quoted and said Solar Edge with power optimizers are better. Any input on this?

He said they are not Tesla Panels but 315W Q-Cells. Anyway to get the Tesla Panasonic 330W or 325W?

I think it is about 12 panels per system, so it should be about 8kw. Maybe they are using 300 watt panels in your case.

The number of powerwalls depends on the type of equipment you have in the house. I presume that you asked them for a whole-house backup. 3 powerwalls can supply 15KW continuously (21kw for 10 seconds). So maybe you have something in your house that requires it. Otherwise, you can probably go with 2 pws.

I think in Hawaii the utilities have some rule about limiting exports to the grid. So maybe 3 powerwalls are designed to be enough to store most of your daily production from 7.5 kw system, which could be up to 50kw per day in Hawaii.


Your power utility may not allow 100% or more than 100%. So they estimate it at 90%. But in reality, they usually estimate conservatively, and your solar production, at least in the first few years may be higher than their estimate. By the way, 3 powerwalls by themselves are likely to consume about 1kwh per day.


SolarEdge with power optimizers is a pretty good and popular solution. It is probably almost as good as micro-inverter in terms of efficiency (maybe tiny bill less efficient, but not enough to care about it). It is easier to expand the system with micro-inverters, but it is not too hard with power optimizers either. In either case, you won't be doing it yourself.

 

[NuShrike]

I asked and he said it only made to off set my bill 90%. Not sure why I wouldn’t want to do 100% ?

They want to make a sale by keeping the system cheap, and keeping the utility happy because you'll still end up paying the utility.

This is grossly ignoring 100% coverage is only on the best days of a sunny summer. Clouds cut output by 2/3rds, winter, dust reduces output by up to 10%, age reduces output by up to 1% every year, ambient temperatures above 25C reduces output, ... Most people are already under "conserving" habits, so 100% doesn't represent normality.

There's so many reasons 200% should be your minimum aim, if you want any longevity out of this system without range-anxiety.

 

[Dan123]

There's so many reasons 200% should be your minimum aim, if you want any longevity out of this system without range-anxiety.

I think it depends on whether you get paid for the extra power that you end up sending to the grid. If you are paid for it, then nice, cover every crevice with solar panels. If you are not paid for it, or paid very little for it, then it does not make financial sense to oversize by 200%.

 

[NuShrike]

I think it depends on whether you get paid for the extra power that you end up sending to the grid. If you are paid for it, then nice, cover every crevice with solar panels. If you are not paid for it, or paid very little for it, then it does not make financial sense to oversize by 200%.

It's looks like Hawaii, so no exports and so probably no FiT anyways.

This thread Switched on my system today! would be the closest model for daily usage and needs.

 

[07stuntar1]

Where are you located? I just had Tesla install Panasonic SC 330 panels at my home. I basically told them I didn't want the Q-Cells and they gave me the 330's

Where are you located? I just had Tesla install Panasonic SC 330 panels at my home. I basically told them I didn't want the Q-Cells and they gave me the 330's

I was able to get them to agree to use the Panasonic 330s