Seeking advice for new solar

[Eric99]

Hello,
I am very impressed with the vast amount if knowledge in this forum. Ive spent numerous hours researching online. Here’s my situation:

-electric bill average $130/mo
-Just bought a model Y so thats not factored in yet (plus not driving quite as much right now)
-planning on re-stuccoing house next year
-want to upgrade my service panel (currently 100 amp)
-have aluminum wiring in the house
(Any additional concern specific to solar)

Does Tesla offer more than what is on their website? I was considering 4kw and 1 PW. But i think 6kw would be better. 8 overkill?
Located in Bay Area Northern California.
Anything else i need to be thinking about?

thanks for any help!
Eric

 

[Electrph]

Hello,
I am very impressed with the vast amount if knowledge in this forum. Ive spent numerous hours researching online. Here’s my situation:

-electric bill average $130/mo
-Just bought a model Y so thats not factored in yet (plus not driving quite as much right now)
Does Tesla offer more than what is on their website? I was considering 4kw and 1 PW. But i think 6kw would be better. 8 overkill?

i can give quick answer to this .. tesla seems to throw you in 4 / 8 / 12kW etc based on what you report as your monthly bill .. i just kept increasing my monthly bill on site until i was given size i thought appropriate .. later during the process you can tweak number of panels / placement but that may require some effort on your part due to tesla wanting to “keep it simple or cookie cutter”
Also generally better from economics to slightly oversize now than add later .. more factors to consider of course, if powerwall(s) for excess storage / how your utility handles your excess production etc

 

[getakey]

Do you have AC? If so, what is peak bill in Summer?

Definitely use PVWatts to get an estimate of annual production. Then compare to your annual usage.

 

[BrettS]

Just a couple of quick thoughts here. When you are looking at sizing a solar system looking at your actual power usage (kWh used per month as well as per year and even a daily average in the summer and winter) can be much more useful than knowing your average power bill cost.

The cost of electricity can vary greatly, so a $130 power bill for you might represent half the power usage that a $130 power bill for me would represent. And with time of use rates two people with $130 power bills in the same area might still have vastly different power usage numbers because they might use their power at different times.

Once you know how much power you are using you can compare that to the amount of power that the solar system you are looking at can produce.

If you are interested in a powerwall you should consider what you want to use it for. If you’re just looking to do load shifting to avoid using power during peak times then a single powerwall on a house with a low power demand might be all that you need. If you want to back up your house in the event of a power outage then it’s unlikely that a single powerwall could back up the whole house. A single powerwall can back up a subset of your critical circuits, but not high power draw circuits like a central AC or an electric oven. You typically need at least two powerwalls to backup every circuit in a house.

 

[charlesj]

Yes, all the above. PG&E will allow you to 110% of last years usage. In your case though since you bought an electric car, that needs to be added somehow especially is you will be driving to work eventually.
I'd recommend to go for that full 110%.
I have a smidge under 4kW and 2 batteries. While it is great for normal grid loss hate to have a loss with all the smoke and fire with minimal solar production. Then you are out of battery quickly no matter how much you turn off. Some you just don't want to, like fridge and freezer if you have one and a number of other appliance usage, cable, internet, etc.

 

[SaveOurPlanet]

I agree with all the advices given here, but you still need to do some homework yourself. As everyone says, your monthly electricity charge is useless because it is biased by baseline or TOC, so take your annual kWh consumption for the last 3 years and take the highest one as baseline. The highest annual consumption + 10% would be what you should start with. PG&E does not give you one-for-one on NEM2 so unless you get lots of sun after 4:00pm you need to make sure you get enough juice from the PW to get you through the peak hours, also you may incur more charges from PG&E for delivery in the future so I think it is best to size enough battery to be self-powered. I ordered only 1 PW because my usage from 4:00pm to 9:00am the following day is around 10 kWh so 1 PW should cover it, but I think 2 PW would let me not worry about rate plan or usage so I asked to add 1 more PW if it would not delay my project. I also have a feeling that Tesla intentionally under estimate the output of the system so you can size a bigger system but still flying under the radar from PG&E.

 

[SMAlset]

Tesla will fill out your PG&E application forms at some point in the process. One of the questions I recall was do you have an EV and if so how many. Pretty sure that helps with the calculations and any exemptions.

OP do you use AC during the summer/fall? Would you want this backed up along with other things on your house?

 

[Eric99]

thanks for the responses. Looking at our past usage, average monthly is appox 550 kWh. 2 months a year it will go up to high 700s (electric heater usage) we only use AC maybe 1 week per year. My goal for the Powerwall is to stay off peak rates. 4-10PM. Backup power is not a huge concern.
Numbers dont include new Model Y charging. (maybe 8-10k miles per year)

 

[Eric99]

4 kWh panels from PVWatts

 

[Eric99]

8 kWh panels

 

[Eric99]

those were if i put the panels on the back side of the roof (would be unseen)
the front of the house numbers are 4kWh=6100/yr and 8kWh=12,200/yr.
thats a big difference

 

[charlesj]

t...
Numbers dont include new Model Y charging. (maybe 8-10k miles per year)

I think you can calculate mileage at 3 mi per kW, that's about 4mWh per year but you could be driving more.
How much have you driven last 12 to 24 mo? and with that car, family may want to drive that all the time. so best to estimate high15k.