Green Button Data in Ontario: Why It Decides Solar Savings (2026)

Last verified October 22, 2026 against the Ontario Ministry of Energy and Mines, the Ontario Energy Board, Home Renovation Savings, Hydro One and Hydro Ottawa.

Green Button data is the most useful input for an Ontario solar savings estimate because it shows your electricity use hour by hour for up to 24 months. That hourly pattern decides how much solar power your home can use itself. On a Home Renovation Savings rebate system, that is the only part that saves money, and it is also the part that decides whether a battery pays.

Want numbers for your own home? Run your address through the free solar and battery estimator for a system size, cost range and payback estimate. It costs nothing and needs no account.

Key takeaways (as of October 22, 2026)

1. Ontario required most regulated electricity and natural gas utilities to offer Green Button by November 1, 2023.
2. The file holds your usage in intervals of one hour or less, with up to 24 months of history.
3. Two homes with identical annual use can land about $300 a year apart on the same 7 kW system, purely because of when they use power.
4. On the Home Renovation Savings path, solar power your home does not use the moment it is made earns nothing, so hourly data sets the right system size.
5. On the Ultra Low Overnight plan, weekday 4 pm to 9 pm use is billed at 37.7 cents per kWh from November 1, 2026, against 3.7 cents overnight. Green Button shows how many kWh your home uses in that window.
6. Download My Data lives inside your utility's online account and comes as an XML file. Hydro One and Hydro Ottawa list no charge for it as of October 22, 2026.

Green Button data is your own electricity usage and account information, provided by your utility in one standard digital format that you can download yourself or share with an app you choose. In Ontario, offering it is a legal requirement for most regulated utilities. The Ontario Ministry of Energy and Mines says the requirement began on November 1, 2021, and that most regulated electricity and natural gas utilities had to provide access no later than November 1, 2023. The rule sits in Ontario Regulation 633/21, the Energy Data regulation made under the Electricity Act, 1998.

There are two parts. Download My Data gives you a file. Connect My Data lets you authorize your utility to send your data automatically to a third party app. The Ontario Energy Board (OEB) says that once you authorize an app it keeps ongoing access, and that you can revoke that authorization at any time by contacting your utility.

The OEB's staff guidance on Green Button, dated November 1, 2021, says usage must be provided in intervals of one hour or less, and that at least 24 months of history must be available unless you have held the account for less time. The usage data it lists includes hourly interval data and energy charges. That is a far richer record than a paper bill. Our Ontario hydro bill guide covers the numbers a bill can give you. This article is about the one number it cannot.

Your annual kilowatt hours tell an installer how big a system to quote. Your hourly data tells you how much of that system's output you will actually use, and only used power saves money on a rebate system.

Here is the plain version. Solar panels make most of their power between mid morning and late afternoon. Your home uses power whenever people are in it. Self consumption is the share of solar production your home uses at the moment it is produced. If the house is empty from 8 am to 6 pm, the panels are making power while the fridge is the only thing running. A home where someone works from home, or where the air conditioner runs all afternoon, uses far more of its own solar.

Think of the panels as a tap that only runs during the day. On a net metering system, the grid holds a bucket under that tap and credits you for what it catches. On a load displacement system there is no bucket. Load displacement means the solar power you generate is used in your own home and nothing goes out to the grid, so without a battery, whatever you are not using at that moment is never produced. A single annual number cannot tell you how much is lost. Green Button can, because it shows what your home was drawing in every hour the sun was up.

The table below compares what each data source can tell you before you sign a solar quote.

Green Button data is essential on the Home Renovation Savings path and useful on the net metering path, because the two paths value unused solar very differently.

As of October 22, 2026, Home Renovation Savings (HRS) pays $1,000 per kW of solar to a maximum of $5,000, and $300 per kWh of battery storage to a maximum of $5,000, each capped at 50 percent of total costs, so up to $10,000 combined. The program page states that recipients are not eligible for a net metering agreement with their utility and that the incentives are for projects designed for load displacement only. A battery is optional, but to qualify for the battery rebate it must be paired with a new solar system. The program says not to buy or install any equipment before you receive written preapproval. Our Ontario solar page sets the rebate beside current costs and rate plans.

On that path, any solar you do not use yourself is lost. Sizing the system to your annual kWh alone can oversize it for a home that is empty during the day. Hourly data lets your installer size to what the house can absorb, which is the method in our zero export sizing guide.

Net metering credits the power you send to the grid. The OEB's net metering page notes that credits can only offset charges for the electricity you consume, not other charges on your bill, and that credits can be carried forward for up to 12 months before they are reduced to $0. Unused daytime solar still has value here, so self consumption matters less for system size. It still matters for choosing a price plan and for checking whether summer credits will run out before winter. Our HRS versus net metering comparison walks through the full decision.

Two Ontario homes each use 9,500 kWh a year, each install a 7 kW rooftop system on the HRS path without a battery, and each sit on the Time of Use plan. Their annual totals look identical. Their savings do not.

Assumptions, stated so you can change them:

• Annual production of about 1,170 kWh per kW, the southern Ontario figure used across this site, drawn from Natural Resources Canada photovoltaic potential data.
• Displaced electricity valued at a single 14.6 cents per kWh, the Time of Use mid peak price effective November 1, 2026. This is a middle value, not the exact price of every solar hour: weekday middays are mid peak in winter and on peak at 18.9 cents in summer, and weekend production is worth the 9.1 cent off peak price. Avoided delivery charges and HST are ignored, so treat this as a simplification.
• Home A has someone home most days and runs air conditioning in summer. Comparing its hourly Green Button file with an estimated solar production curve shows it would use about 60 percent of its solar as it is made.
• Home B is empty on weekdays. The same comparison shows about 35 percent.

Both percentages are illustrative. Your own file, matched against a production estimate for your roof, gives you your real number.

The gap is about $300 a year, or roughly $7,500 over 25 years before panel ageing or price changes. Without a battery, Home B's remaining 5,323 kWh of potential production earns nothing: the HRS path rules out net metering credits, so a zero export design curtails that power instead of sending it to the grid. A quote built on an annual total cannot show that number. Green Button exposes it in an afternoon. The fix for Home B is not to give up on solar. It is to size smaller, shift loads such as a dishwasher or EV charger into daylight, add a battery, or pick net metering instead. Your file, run through an estimate, helps you decide which.

See what your real usage pattern does to the numbers. The estimator gives you a system size, cost range and payback range for your home. Estimates only, no credit card, no account.

A battery only earns money on the hours it replaces, so the kilowatt hours your file shows between 4 pm and 9 pm on weekdays set the ceiling on what a battery can save you through price shifting on the ULO plan.

The Ultra Low Overnight (ULO) plan has the widest price spread of Ontario's regulated price plans. These are the prices the OEB set effective November 1, 2026. Hydro One's ULO page confirms that weekends and holidays are off peak until 11 pm, then ultra low until 7 am.

Say your Green Button file shows an average of 5 kWh of use between 4 pm and 9 pm on weekdays. Each kWh moved from on peak to overnight saves 37.7 minus 3.7, or 34.0 cents. 5 kWh × $0.34 = $1.70 per weekday. Roughly 250 weekdays a year, once holidays are removed, gives about $425 a year before battery losses. A 15 kWh battery would be oversized for that job. If the file shows 12 kWh in that window because of electric heating or evening EV charging, the same math gives about $1,020 a year. Our TOU versus ULO comparison helps you decide whether to switch plans at all.

You download Green Button data from your utility's online account in a few clicks. The exact menu differs by utility.

1. Log in to your utility's online account. Hydro Ottawa also lets you sign in to its Green Button portal with your 20 digit account number, total kWh consumption and bill due date from your latest bill.
2. Find the Green Button icon or link. Hydro One customers log in to myAccount and click the Green Button icon shown below Account Strength. Other utilities place it under usage, smart meter or downloads.
3. Choose Download My Data and pick the longest date range offered. Hydro One and Hydro Ottawa both offer up to 24 months, and Hydro Ottawa has a request form for data older than that. Hydro Ottawa says its data uses the same intervals your smart meter records, such as 15 minute or hourly readings.
4. Save the file. Hydro One provides it in XML, which it describes as raw data. XML is built for software, not for reading by eye. If your utility also offers a spreadsheet (CSV) version, that one opens in Excel or Google Sheets. Either way, a competent installer can work with it.
5. Optional: share automatically. Connect My Data sends your data to an app you choose. Read how the app handles your data first, because once you share it, Hydro One states it is no longer responsible for your data.

Green Button data is a record of the past, and five things can make the past a poor guide to the future.

• Your household changed. A new EV, heat pump, hot tub or home office makes last year's file understate next year's use. Adjust upward and tell your installer.
• Gaps and estimates. Hydro Ottawa warns that gaps or estimates may occur because of outages, meter issues or communication problems. A stretch of estimates flattens your real hourly pattern.
• Less than 24 months. A new account gives you less history. One winter and one summer is the minimum you want.
• The file says nothing about your roof. Orientation, pitch, shading and roof age change what the system produces.
• Sharing without reading. The OEB says it is your responsibility to understand the terms you accept, and recommends asking an app what it will do with your data before you authorize the transfer.

Answer these before you accept any savings number.

1. Did the estimate use your hourly Green Button data, or only an annual total?
2. If you are on the HRS path, does the quote state your expected self consumption percentage?
3. Does the system size reflect what your home can absorb in summer daytime, not just your annual kWh?
4. If a battery is included, does the quote show your weekday 4 pm to 9 pm kWh and the ULO math behind it?
5. Did anything change in your household in the past 12 months that the file does not reflect?
6. Did the installer ask for the file at all? If not, ask why.

Download the file today, then put it to work before you talk to anyone selling panels.

Get an estimate built on your real usage. Enter the monthly totals from your file in the free Solar Calculator Canada estimator for a system size, cost range and payback estimate. Estimates only, no credit card, no account.

Solar Calculator Canada is an independent Canadian platform that provides free solar and battery estimates and matches homeowners with vetted installers. We do not install equipment. If you ask to be matched with installers, your details may be shared with vetted installers in our network and we may earn a fee from that match. Running an estimate on its own does not require it. You can read how we vet installers before you decide. No permit, inspection, utility approval, rebate or install date is guaranteed until the approvals are complete.

Editorial note: The figures on this page are estimates built on stated assumptions and on Regulated Price Plan prices effective November 1, 2026. The Ontario Energy Board sets these prices once a year on November 1. Home Renovation Savings terms and utility Green Button menus change, so confirm with the program and your utility before you buy. This article is informational and is not electrical, financial or legal advice.

1. Ontario Ministry of Energy and Mines, Lower your energy bills with Green Button.
2. Government of Ontario, O. Reg. 633/21: Energy Data, under the Electricity Act, 1998.
3. Ontario Energy Board, Green Button.
4. Ontario Energy Board, OEB Staff Guidance for Implementation of Green Button, November 1, 2021 (PDF).
5. Ontario Energy Board, Electricity rates.
6. Ontario Energy Board, Net metering.
7. Home Renovation Savings, Solar panels and battery storage.
8. Hydro One, Green Button.
9. Hydro One, Ultra-Low Overnight price plan.
10. Hydro Ottawa, Green Button.
11. Natural Resources Canada, Photovoltaic potential and solar resource maps of Canada.