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The house remained cool, and the battery reached a full charge.
Photo Credit: iStock
A homeowner in Belgium took to the r/solar subreddit to highlight what rooftop solar can do in extreme summer weather. During a 99 degrees Fahrenheit (37 degrees Celsius) heat wave, their setup kept the house cool while almost no electricity was needed from the grid.
In a post on Reddit, a homeowner from Belgium said their 18-panel system generated 31.3 kilowatt-hours during the heat wave, with the heat pump and air conditioning running throughout the day.
“31.3 kWh solar day keeping the heat pump and AC on all day long in 37C weather,” they titled the thread.
According to the post, the house remained cool, the battery reached a full charge, only 0.03 kilowatt-hours came from the grid, and 7.8 kilowatt-hours were still exported during times when the sun’s power far exceeded their usage. With all that in mind, it’s not surprising they wrote “can’t complain” to wrap up the post.
The day produced enough power not just to handle the cooling load but also to fully charge the home’s battery and leave extra electricity to send back out, offering a clear example of home energy independence in oppressive heat.
Results like this help show why some homeowners pair rooftop solar with electric heating and cooling. Heat pumps can manage indoor temperatures efficiently, and adding solar teamed up with battery storage can greatly reduce the cost of staying comfortable.
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Here, the reported 0.03 kWh taken from the grid is almost nothing, while the 7.8 kWh sent back out could become bill credits depending on local policies.
There is also a reliability angle. Heat waves often push electricity demand higher as air conditioners kick on across entire neighborhoods, so homes that generate their own power can reduce pressure on the grid and limit homeowners’ exposure to peak pricing and surprise utility bills.
Anyone interested in building a similar system can use EnergySage to compare free bids from local solar installers. For people more focused on cooling, EnergySage can also help connect them with heat pump installers, while Merino offers ultra-efficient single-room HVACs that can be installed at a lower price point.
A commenter from Midland, Texas, said they recorded roughly similar performance that same day in 100F weather while running a 4-ton heat pump. They called it a “happy coincidence,” and it added a U.S. heat-wave comparison to the thread.
“Way cool!” another user said. “In the news this morning I see there is a heatwave in the EU and UK, and the houses there are mostly not refrigerated.”
Good as the OP’s story was, one poster wanted even more for them.
“A little more air-sealing/insulation or other efficiency improvements would easily give you an energy cushion,” they wrote.
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© 2025 THE COOL DOWN COMPANY. All Rights Reserved. Do not sell or share my personal information. Reach us at hello@thecooldown.com.

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