If you're thinking about a home battery, we'd like to design it around how your home actually uses electricity. A battery's value depends on when you use power, not just how much. ComEd's smart meter records your usage every half hour, and ComEd lets you download that record through a feature called Green Button.
This guide shows you how to download a year of that data and send it to us. It takes about five minutes.
Watch the steps
Here's the whole process at a glance. We describe each step in detail below.
Before you start
- Make sure you have access to your ComEd account online. If you don't have one yet, go to comed.com and click Create Online Account. Keep a recent ComEd bill handy in case ComEd asks for your account number.
- Plan to use a computer for this. We wrote these steps on a computer. ComEd's screens look different on a phone.
- Decide which dates to use.
- Best: the year ending the most recent May 31. As of this writing in September 2026, that's 6/1/2025 to 5/31/2026. This may seem a bit old, but it helps us model certain ComEd charges as accurately as possible.
- If you haven't lived in your home that long: Any complete year works. For example: 9/29/2025 to 9/28/2026.
Less than a year in your home? This method needs a full year of your usage. If you haven't lived in your home for a year yet, talk to your sales consultant or email info@certasun.com about other options.
Download your data
1. Open My Usage
Sign in at comed.com. Click My Account in the menu at the top of the page, then click My Usage at the bottom of the first column.
2. Open My Green Button Data
On the My Usage page, click the card called My Green Button Data. The page can shift a little while it loads, so give it a moment before you click.
3. Click the Green Button
Make sure you're on the Download My Data tab. Then click the green Green Button – Download my data button on the right.
4. Choose "Export usage for a range of days"
A panel called Download my data opens. Under Time Period, click Export usage for a range of days. Leave Format set to CSV.
Watch out: ComEd starts with Export all bill totals selected. That option gives only one number per month, which isn't enough for us to design a battery. Be sure to switch to the range of days.
5. Enter your dates
Type the To date first, then the From date, using the dates from Before you start. You can also pick them from the calendar next to each box.
Why the To date first? ComEd won't accept a range longer than one year. Until you change the To date, it still shows today's date, so a From date from last year makes the range too long.
If you see this message and the Export button turns gray, check that your two dates are no more than a year apart.
6. Click Export
Click Export. ComEd says the export can take up to a minute, so give it time.
Send the file to us
ComEd saves a ZIP file to your computer's Downloads folder. Its name starts with cec- and ends with DailyUsageData.zip. (The name says "Daily," but the file holds your usage for every half hour.)
You don't need to open or unzip it. Attach the ZIP file to an email to your Certasun consultant, just as ComEd saved it.
The file contains your name, service address, and ComEd account number, along with your half-hour usage and estimated cost. It doesn't contain your ComEd password. Please never share your password with us or anyone else. We'll never ask for it.
About the cost numbers in the file
Next to each half hour of usage, the file shows a cost. Please don't read it as your bill. ComEd calls these costs estimates, and they cover only part of your bill: some of the charges that go up or down with each kilowatt-hour (kWh) you use. The costs leave out your other charges, including your fixed monthly charges and taxes, so they won't add up to what you actually paid.
We don't use that column. We use your usage and apply ComEd's current published rates to it.
If something doesn't look right
- The Export button is gray. Your dates are more than a year apart. Change the To date first, then the From date.
- You have more than one ComEd account. Before step 1, make sure the account shown on your ComEd dashboard is the home where the battery would go.
- You've lived in the home less than a year. This method won't work yet. Talk to your sales consultant or email info@certasun.com about other options.
- You opened the file in Excel. That's fine, but please don't save it from Excel. Excel can change the file's formatting. If you already saved it, just download a fresh copy from ComEd.
If you get stuck, contact your sales consultant or our broader team at info@certasun.com or (312) 638-0800. We're happy to help.
This post was written by Jenny Schwabacher.
