NorCal: Ordered small solar + Powerwall

[kpinthebay]

Thought I'd share my ordering and thought process for potential new solar customers in a similar situation as us.

As I saw our electric bill slowly creep up, I got the approval from the mrs to go ahead with Tesla solar. Although we've been pestered by a Sunrun door to door sales guy for years, we went with the Tesla system. Why? 1) I like the online experience 2) I like the small/med/large package system 3) I like that they don't try to upsell you 4) Last - I love their pricing.

After studying my electric bill (PG&E), I initially ordered only the the small 4kw system. My goal wasn't to be completely reliant on solar, but just to defray some cost and to do my part to reduce some of our household's carbon footprint. After placing my order, I had thoughts on whether I wanted to do a Powerwall. There's a split camp for PW on youtube and the forums, but I figured since Tesla offered a package discount and I got a bigger tax credit, I might as well just do it. So I emailed and called a few numbers and was able to add a single PW to my order.

Now, here in Norcal my electric rates range from 16.6 cents to a whopping 48 cents during summer peak. Unreal. The 16 cents only applies from midnight to 3pm. My plan is to (obviously) have solar power available during sun hours, and hopefully use the PW from sundown to midnight, and maybe some after. I checked my bills and on normal non SIP workweeks, our usage spikes during the dinner hours. So if I can shift our dishwashing and laundry to off peak, I'm sure I can get below the 13.5 kw capacity of the PW.

Not to mention the peace of mind knowing we have backup power should we lose grid power. Happened a few times last year.

Pretty excited, but we'll see how long it takes for everything to happen. I will update this thread (hopefully) in a few months for my user experience.

 

[jrweiss98020]

If you are trying to work with Time Of Use pricing, more Powerwalls and more solar production capacity will be better. You want to avoid using any electricity during peak hours, so you want to be able to run the house AND recharge the PW - all from solar - during the peak. Unless you are VERY frugal with electricity, a small system like that will likely disappoint...

 

[jboy210]

Your usage sounds like most people. People come home from work and start cooking, turning on AC, etc and the usage and prices spikes.

Your plan do laundry late at night works. But you only need to worry about the dryer. The washer uses relatively little power.

There are a few things to consider about just have one powerwall that may make you rethink the decision.

• First is that you are likely going to have a separate panel that covers "critical" loads only. Lights, outlets and a few other things. Big power consumers like AC, oven, dryer may not be backed up since a single powerwall only outputs 5kW. There will be a cost to install this new panel.
• Second, the cost of installation includes items that like the gateway that are the same whether there are are 1, 2, or even 4 powerwalls. So the relatively cost to upgrade to a second powerwall is the more or less the cost of the second Powerwall.
• Third the federal tax credit is expiring. So the credit you get for installing a second PW will be less than the 26% your get this year if you decide you want to install a second Powerwall next year or later.

I went through this same analysis and went with 2 PWs.

 

[aesculus]

As @jboy210 states, the 5 kW you are limited to with 1 PW is a killer when trying to run an AC and do anything else. 2 PWs seems to be the sweet spot. And also you need to then match the solar to fill up the PWs enough so you can get through peak with no grid use and in fact send whatever you are producing then back to the grid for cost offset.

Be careful with rated solar capacity vs real solar capacity. Have the vendor verify your true solar production for the day.And if you might experience PSPS events you need at least as much solar as your minimum daily consumption. Any more than that and there will be not place for it to go during a grid outage but that probably won't happen that often anyway.

 

[cwied]

I would actually calculate the Powerwall sizing to last until solar production matches your home load the next morning, since this is what you would have to cover in the case of a power outage. Of course if cost is a prohibitive factor, anything is better than nothing, but being able to cover both the load shifting and power outage gives me a lot of peace of mind.

 

[wjgjr]

I would actually calculate the Powerwall sizing to last until solar production matches your home load the next morning, since this is what you would have to cover in the case of a power outage. Of course if cost is a prohibitive factor, anything is better than nothing, but being able to cover both the load shifting and power outage gives me a lot of peace of mind.

Yes - this makes the most sense, where cost is not a factor. And, as others have noted, in I think the vast majority of cases this - and the 5kW limit for continuous usage - will result in the need for at least 2 powerwalls.

One other note for OP is that it seems like Tesla is flexible on the sizing after you pick the initial option , so if it turns out that say 15 panels would be a perfect sizing for your needs, budget, and roof, it sounds like they would help make that happen. It seems like the S/M/L/XL is just a way to make it easier for customers to generally conceptualize their system (which makes sense as it is easier to start with 4 options based on your own budget, production, and roof constraints than with 40+ options.) But, once you get in the door, they will work with you to further refine the system, if you choose to do so.