Are Home Solar Batteries Safe? What the Summerside Fire Does and Does Not Tell You

Home solar batteries are safe in normal use, and fires in them are rare. Lithium iron phosphate, the chemistry used in many home batteries, is one an expert who has studied lithium cells since 1978 calls “very uncommon” to catch fire, and certified home battery storage includes a battery management system designed to prevent overcharging, one known cause of cell failure. The fire burning at Summerside’s Sunbank solar farm since Sept. 7 began in one of the battery banks at a grid site whose battery capacity is rated at 20 megawatt hours, orders of magnitude more than anything mounted on a house.

What Happened at the Sunbank Solar Farm

A fire began in one of the large battery banks at the city’s Sunbank solar farm in Summerside, P.E.I., at about 5:30 a.m. on Sept. 7, Labour Day, CBC News reported. The 30 hectare west end site houses thousands of solar panels, CBC reported a week later. The fire prompted an immediate shelter in place order, a voluntary evacuation notice, road closures and two school closures the following day, according to The Canadian Press.

The shelter in place order was downgraded to a voluntary advisory and then lifted. On the night of Sept. 9 a cell that was believed to have burned out ignited again at about 9 p.m., so the city reinstated the voluntary warning and widened the affected zone. Crews had the fire back under better control by early the next morning, the city lifted the notice again that evening, and the P.E.I. Public Schools Branch said students were expected back Friday, CBC News reported. On Sept. 10, P.E.I.’s chief public health officer, Dr. Heather Morrison, said air quality monitoring confirmed the gasses did not pose a threat to residents, citing toxicology experts at the Atlantic Poison Control Centre in Halifax. “It is safe to exercise and be outside,” she said.

By the seventh day the fire was confined to a single battery cell, down from two earlier in the week. It was still burning on Sept. 17, with the city and province calling the situation stable and Dr. Morrison saying residents should feel confident in both the air and the drinking water. The city is developing a longer term plan for air, water and soil sampling around the site.

No cause has been announced, and officials have not determined what started the fire.

Why a Utility Battery Bank Is Not the Box on Your Wall

The scale difference is the part most coverage skips. The Sunbank farm cost $69 million, was energized in January 2024, and runs 48,000 solar panels producing 21.6 megawatts, with battery capacity rated at 20 megawatt hours, The Canadian Press reported. That rating covers the farm as a whole, not the single bank that caught fire.

Home batteries are rated in kilowatt hours, not megawatt hours. Twenty megawatt hours is 20,000 kilowatt hours, so a single home unit holds a tiny fraction of what is stored at Sunbank. That unit conversion is ours, applied to the published rating.

Scale changes the problem. A grid site packs enormous quantities of cells into enclosures that crews cannot easily reach once a fire starts, which is why the Summerside blaze was left to burn itself out under round the clock monitoring rather than extinguished. A wall mounted home battery is a single certified appliance, installed by a licensed electrician, in a location an occupant can walk away from.

What Thermal Runaway Is, and What Is Designed to Stop It

Thermal runaway is the failure mode behind almost every serious lithium battery fire. A 2023 report from the U.S. based Fire Protection Research Foundation, cited by The Canadian Press, says lithium ion batteries can catch fire when damaged by impacts or exposed to water, and that under certain conditions either can push cells into an uncontrollable temperature rise ending in fire or explosion.

The same report explains why these fires are stubborn: the reaction inside a damaged cell creates flammable gasses that are self sustaining and resist traditional firefighting. Water often cannot reach or cool the internal reaction, and the risk of reignition remains high even after a fire appears to be out. For that reason, the report says, codes and standards focus on prevention, early detection and containment rather than extinguishment.

That is also why a modern battery is built in layers. Jeff Dahn, a professor of physics and atmospheric science at Dalhousie University who has researched lithium batteries since 1978, told CBC News it is “very uncommon” for a lithium iron phosphate battery to catch fire.

“If a cell is repeatedly overcharged, it can cause problems, but that is generally prevented by the battery management system,” Dahn said. He added that electric vehicles and energy storage systems are designed so that if a single cell goes into thermal runaway, its neighbours do not, often using thermal barriers such as fire retardant foams placed between the cells.

Dahn called such fires “very, very rare” and said lithium ion safety is continually improving, pointing to electric vehicles as the everyday comparison: broadly similar cells, a great many of them on the road, very few fires.

How Home Batteries Are Certified in Canada

A home battery sold in Canada is not an unregulated product. According to CSA Group, residential energy storage systems typically require a certification mark from a nationally recognized testing laboratory. Three standards carry most of the weight:

• ANSI/CAN/UL 1973 covers cells, modules and battery systems used in stationary applications, and includes safety criteria for well known battery chemistries alongside construction and testing criteria.
• UL/CAN 9540 is the binational standard for energy storage systems as a whole, including functional safety measures and electrical, mechanical and environmental testing.
• UL 9540A is the test method for evaluating thermal runaway fire propagation, the exact behaviour described above.

Installation is governed separately by the Canadian Electrical Code and by provincial electrical and fire codes, which is why a battery needs a permit and an inspection rather than a weekend afternoon.

Are Home Solar Batteries Safe Enough for Your House? Five Questions to Ask

• What cell chemistry does this battery use, and is it lithium iron phosphate?
• Which certification marks does the unit carry, and can I see them on the nameplate?
• Does it have a battery management system, and what does that system do if a cell overheats or overcharges?
• Where will it be mounted, and does that location meet the Canadian Electrical Code and my municipal fire code?
• Who pulls the permit, and who performs the inspection?

An installer who cannot answer these plainly is the actual risk. A certified unit, correctly placed and inspected, is a well understood appliance.

Related Questions

Can a home battery fire be put out?

Not easily, which is why prevention matters more than suppression. Water often cannot cool the reaction inside a damaged cell. Tell your fire department the battery is there, and keep it accessible.

Is lithium iron phosphate safer than other lithium chemistries?

It is the chemistry Dahn described as “very uncommon” to catch fire, and it is widely used in home storage products. No lithium chemistry is immune, which is why the protections that matter are certification, the battery management system and correct installation.

Should the Summerside fire change my plans?

On the evidence available, no. One grid scale battery bank failed, the cause is still unknown, air and water testing found no risk to residents, and the specialist most quoted on the incident called such fires very rare. If it has made you cautious, put that caution into the questions above rather than into abandoning storage.