Batteries and Storage

Solar batteries store electricity your panels produce during the day so you can use it later in the evening, overnight or during a power outage. Without a battery, a grid-connected solar system sends any excess electricity to the grid through net meteringA solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months. and draws from the grid when the sun is not shining. A battery gives you the option to keep some of that electricity for yourself.

The batteries used for home solar are larger and more expensive than anything you would buy at a hardware store. Whether they are worth the cost depends on what you want them to do.

There are three ways homeowners use batteries. Most systems are set up for one or a combination of these.

Your solar panels often produce more than your home needs during the middle of the day. Instead of sending that surplus to the grid, a battery stores it and supplies your home in the evening and overnight. This means you buy less electricity overall. Systems set up this way typically cycle the battery once a day for most of the year.

Ontario's time-of-use pricing charges more for electricity during peak hours. A battery can charge overnight when rates are lowest and supply your home during peak-rate periods, reducing the cost of the electricity you do buy from the grid. These systems are typically sized to cover your home's peak and some mid-peak hours.

A battery can power critical loads, such as your fridge, freezer, furnace fan and a few lights, when the grid goes down. Without a battery, a grid-connected solar system shuts off automatically during outages to protect hydro workers. Backup systems are typically sized to last a day or two on essential loads.

A common assumption is that solar panels with a battery will power your entire home indefinitely during an outage. They will not. That would require a very large battery and a solar system designed to recharge it even during the lowest-production months. The smaller the load you put on the battery during an outage, the longer it lasts.

If your battery is sitting fully charged waiting for an outage, you can also use part of its capacity for daily time-of-use shifting. The trade-off is that during a shifting cycle the battery depletes and needs to recharge. If the power goes out during that window, your backup is reduced. To manage this, you can reserve a portion of the battery's capacity for backup while the rest cycles daily. This may mean a larger battery. Your solar installer will help you find the right balance and program the battery accordingly.

Most of this resource hub focuses on the most common residential solar setup: grid-connected panels without batteries, using net meteringA solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months.. Batteries change the picture in one important way.

Ontario's Home Renovation Savings Program (HRSP) offers rebates of up to $5,000 for solar ($1,000/kW) and $5,000 for battery storageA system that stores solar electricity for later use, typically during power outages. Batteries are optional and are not required for net-metered solar systems. ($300/kWh). But there is a trade-off: if you take the HRSP solar rebate, your system is not eligible for net meteringA solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months.. Any excess electricity you export to the grid receives no credit on your hydro bill.

In practice, this means battery systems paired with the rebate usually have weaker financial performance than net-metered systems without batteries, even after accounting for the rebate. Net-metered systems without batteries typically pay back in 12-18 years. Batteries may still be the right choice for homeowners who want backup power, want to reduce grid dependence or have high evening electricity use.

See Government Financing and Incentive Programs for full HRSP details

See Net MeteringA solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months. section for how net meteringA solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months. works

Everything above applies to homes connected to the grid. Fully off-gridA solar system that is not connected to the electrical grid. Off-grid systems rely on batteries and often a backup generator and are typically used in remote or seasonal properties. solar and battery systems, where you disconnect from the grid entirely, are expensive, complex to design and require ongoing monitoring. They are a lifestyle choice, not a cost-saving measure, and are typically only practical for remote properties without grid access. This section does not cover off-gridA solar system that is not connected to the electrical grid. Off-grid systems rely on batteries and often a backup generator and are typically used in remote or seasonal properties. systems.

Most homeowners who add battery storageA system that stores solar electricity for later use, typically during power outages. Batteries are optional and are not required for net-metered solar systems. do so for backup power or greater independence from the grid, not because batteries improve their financial return. There are a few situations where a battery may also save money:

• Small roof, high electricity use. You would not be able to offset enough of your consumption through net meteringA solar system configuration that allows excess solar electricity to be sent to the grid in exchange for hydro bill credits. These credits can then be used to offset future electricity imports. In Ontario, unused credits expire after 12 months. alone, so storing and using your own production would be more valuable.
• High evening consumption. You already benefit from ultra-low overnight (ULO) rates, often because you charge an EV or plug-in hybrid overnight, and a battery lets you shift more of your use to those cheap hours.

Your HSA Advisor will let you know if your consumption profile and roof make storage financially worthwhile.

Home backup batteries cost more upfront than a portable generator and require professional installation. They also operate quietly, produce no emissions, need no fuel and recharge from your solar panels. For homeowners who want backup power without the noise, exhaust and ongoing fuel costs of a generator, a battery is the alternative.