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The Kelly Family's Solar Battery Journey
When the Kelly family installed solar panels on their home in County Kildare two years ago, they were happy with the savings but frustrated by one thing: exporting large amounts of surplus generation to the grid for a fraction of what they paid for imported electricity. The solution was obvious — add battery storage. What they didn't expect was just how transformative it would be.
The Original Solar Installation
The Kellys' initial installation was a 5kW system with 14 Jinko panels, installed in early 2024. The system generated approximately 4,200 kWh in its first year, but with both parents working during the day, they were only self-consuming about 35% of their generation and exporting the rest. At the Clean Export Guarantee rate of approximately 6c per kWh, their annual export income was just €160 — while the exported energy was worth over €800 at import rates.
"We were essentially giving away €600+ worth of electricity to the grid every year," says Aisling Kelly. "That's when we started looking seriously at battery storage."
Adding a Tesla Powerwall
In April 2025, the Kellys added a Tesla Powerwall 2 (13.5kWh usable capacity) to their existing solar system. The SEAI battery retrofit grant of €600 applied, reducing the installed cost from approximately €7,500 to €6,900.
"The installation took half a day," recalls Aisling. "They connected the Powerwall to our existing inverter and set up the Tesla app. Within hours, we could see exactly when the battery was charging, how much it was storing, and when it was discharging."
The Results: 47 Days Off-Grid
The summer of 2025 was exceptional for solar generation in Ireland, and the Kellys' system with battery storage delivered remarkable results:
- Self-consumption increased: From 35% to 92%
- Grid imports during summer: Effectively zero for 47 consecutive days (late May to mid-July)
- Annual electricity bill: Reduced from €1,800 (pre-solar) to €380 (with solar + battery)
- Annual export income: Reduced to €40 (most surplus now stored in battery)
- Net annual saving: €1,420
"Going 47 days without touching the grid was incredible," says Aisling. "Even on cloudy days, the battery had enough charge from the previous sunny days to get us through the evening and night. It genuinely felt like we'd achieved energy independence."
Is Battery Storage Right for You?
The Kellys' experience shows that battery storage can be transformative, but it's not for everyone. The economics work best when: you're out during the day (meaning lots of surplus generation), your electricity tariff has peak pricing (making stored solar more valuable), and you have a sufficiently large solar system. For households where someone is home all day, the battery benefit is smaller because more solar is already self-consumed.
Frequently Asked Questions
How many days can a solar battery last off-grid?
The Kelly family achieved 47 consecutive days of zero grid imports during summer with a 13.5kWh Tesla Powerwall and 5kW solar system.
Is a Tesla Powerwall worth it in Ireland?
For the Kellys, the Powerwall increased self-consumption from 35% to 92% and reduced their annual bill to €380. The payback on the battery alone is approximately 6 years.
Can I add a battery to an existing solar system?
Yes. Battery retrofit is straightforward and can be done in half a day. The SEAI offers a €600 grant for battery retrofits to existing solar systems.