Ready to place order for panels

[isjka]

Hi,

I'm ready to place an order on the site for panels here in IL. From what I've read , the IL block program incentives come off the top making it more palatable from a cost standpoint. We also have net metering available to us in IL and I'm already on the hourly rate with ComEd. I used ComEd's solar calculator today and it estimated 9.7 kw for 11,452 with a 110% offset of the last 12 months.

What size should I order 8.16 or 12.24? And how does Tesla handle the referral codes? I would think ComEd would reject the 12.24 based on the 110% offset rule with net metering, but wasn't sure from an order perspective which router makes the most sense.

Thanks for any tips.

 

[willow_hiller]

With net metering, it usually makes the most economic sense to size your system to around 100%. 110% would be a good benchmark for decreases in production over time or if your consumption goes up slightly.

Do you know about how many kWh you consume annually? PVWatts is my favorite calculator to figure annual output: PVWatts Calculator

It's saying in Chicago, a South-facing 8.16 kW system will generate 10,695 kWh per year on average, where a South-facing 12.24 kW system will generate 16,042 kWh per year. Tesla can design a system in-between the two sizes for you, you just need to ask for it over the phone or by email after placing an order. The best number I've found to reach them is 877-571-7652.

With referral codes, you must place your order through the referral link. Attempts to add referral codes after placing the order are usually not honored. Let me know if you need a code. If you already have a Tesla account, you can also use your own referral code, but the same rule applies.

 

[wjgjr]

If I am understanding you correctly, ComEd won't approve anything that is set to generate over 110% of your last year's production (and it sounds like 110% = 11,452MW) if you want to take advantage of net metering. I would be tempted to start with the larger size and have Tesla downgrade you. Tesla will do their own estimates, but based on these numbers, it sounds like they should settle on 28-30 panels to meet the ComEd rules. And Tesla should be familiar with the rules - they generally do seem to be aware of them - but if you pick the large, it is possible they will just come back with 36 panels in the first draft, and you will have to remind them of the ComEd restrictions. Whether you pick the 8 or 12kW system, you will, based on what a number of people on this forum have found, have opportunity to customize the system before finalizing everything.

 

[holeydonut]

Can you tell your utility that you are buying an EV or how you're impacted by COVID sheltering with more energy use at home?

 

[isjka]

Thanks for all the info here. I don't think ComEd will budge on the 110%. There is even some fine print that states if you don't have 12 months of usage they use some type of average.

I'll order the larger system then call as suggested. How long should I wait until I phone them after the order is placed?

 

[willow_hiller]

I'll order the larger system then call as suggested. How long should I wait until I phone them after the order is placed?

You should be given an opportunity to upload your utility bill shortly after ordering, and then you'll get your layout within a week. If you're feeling patient, you could see if they see your utility from the bill and limit it to 110% by themselves when you get the layout.

Or if you want to ensure they design it that way from the start, you could give them a call right after uploading your utility bill.

 

[AcerMe]

Thanks for all the info here. I don't think ComEd will budge on the 110%. There is even some fine print that states if you don't have 12 months of usage they use some type of average.

I'll order the larger system then call as suggested. How long should I wait until I phone them after the order is placed?

I ordered the 8kW system and the first layout they provided they had already determined my max allowed by ComEd and sized me down to 6kW.

Also with me being home since March and not charging my car much, energy usage dropped a bit year over year. I tried making a case for a bigger system but they did say ComEd is firm in the 110% rule. I know other utility companies allow exceptions but looks like a no go for me.

The flipside is recent months usage is higher year over year with AC running all day...so I don't know how big of a difference it really is.

 

[isjka]

I placed the order for the larger size and it was modified - no real big surprise there. What I did find out is that my PV Watts max output per ComEd is 10,594 kwh. That does seem to correlate to my last 12 months +/- 10%. Tesla estimated a system at 7.82kw producing 8,511 kwh per year. When I asked about the difference, I was told Tesla estimates more of a real world scenario. When I plug 7.82 into PV Watts for my area, I do come up with a range between 9,734 and 10,594. Does Tesla really underestimate that much? Can't really get through to ComEd this week due to power outages.

Here is the design. There are no more vents on the side of the roof where no panels exist. I was told that didn't matter since that side wouldn't produce as much. Seems to look decent. Thoughts?

 

[willow_hiller]

When I plug 7.82 into PV Watts for my area, I do come up with a range between 9,734 and 10,594. Does Tesla really underestimate that much?

They underestimate some. Are you accounting for your roof pitch and azimuth (system cardinal direction) on PVWatts? PVWatts defaults to a good pitch and a purely South facing system, so if you don't adjust those it will give you an overestimate.

 

[isjka]

I actually used the same parameters as Tesla did. They did change the pitch and azimuth from the defaults. It just seems like a huge underestimate.

 

[isjka]

Order placed......