How a Lisburn Family Cut Their Electricity Bill by 65% with Solar Panels

This case study is a representative example based on typical results for a household of this type in the Lisburn area. The figures reflect real-world performance data from similar installations across Northern Ireland.

When the Murphy family moved into their three-bedroom semi-detached home in Lisburn in 2019, their electricity bill was manageable. By 2024, it had nearly doubled. With two young children, a growing number of devices to charge, and electricity rates climbing past 25p per kWh, they decided it was time to look at solar panels seriously.

Why they chose solar

“We had been thinking about it for a couple of years,” says Sarah Murphy. “Every time a price rise letter came through the door, we would talk about it again. Eventually we just decided to stop talking and get some quotes.”

The family’s main motivation was straightforward: reduce their electricity bills. They were spending around £1,200 per year on electricity, which felt unsustainable for a household trying to save for the future. Environmental considerations played a part too, but the financial case was what tipped the decision.

The system they installed

After comparing quotes from three local MCS-certified installers, the Murphys chose a system comprising:

• 10 x 400W solar panels (4kW total capacity), installed on their south-facing rear roof
• A 5kWh GivEnergy battery, mounted in the garage
• A GivEnergy inverter with smart energy management
• Total cost: £7,800 (inclusive of VAT at 0%)

The installation took a single day. The installer handled all the paperwork, including DNO notification and MCS registration. The family was generating electricity by teatime.

12 months of real results

After a full year of operation, the numbers tell a compelling story.

Generation: The system produced 3,480 kWh over 12 months. This was slightly above the installer’s estimate of 3,400 kWh, helped by a particularly sunny May and June.

Self-consumption: Thanks to the battery, the family used 72% of their solar generation directly. The battery charges during the day when the panels are producing and discharges in the evening when the family is cooking, watching television and running the washing machine. Without the battery, self-consumption would likely have been around 35% to 40%.

Grid imports: Their grid electricity purchases dropped from 4,200 kWh to just 1,700 kWh over the year. That is a reduction of nearly 60%.

Export income: The 28% of generation they did not use (around 974 kWh) was exported to the grid, earning them approximately £68 in export payments.

Total annual savings: Combining reduced bills and export income, the family saved approximately £780 in the first year, a 65% reduction in their electricity costs.

Month by month variation

The savings were not evenly distributed across the year, as you would expect. During June and July, the Murphys’ electricity bill was effectively zero, with the system generating more than enough to cover all their needs and the battery handling the evening demand.

Winter was a different story. December and January saw much lower generation, and the family relied on grid electricity for a significant portion of their needs. Even so, the battery helped shift some cheap overnight electricity into peak hours, trimming costs further.

Across the full year, the pattern averaged out to consistent and meaningful savings.

What they would do differently

Asked what they would change about the experience, the family had just one observation.

“We would probably have gone for a slightly larger battery,” says Sarah. “The 5kWh is great, but on long summer evenings we sometimes have excess solar that the battery cannot absorb because it is already full. A 9.5kWh battery would have captured more of that, though obviously it would have cost more upfront.”

They also wished they had started the process sooner. “We spent two years thinking about it. Looking back, that is two years of savings we missed out on.”

The payback calculation

At £780 per year in savings, the system’s £7,800 cost gives a simple payback period of exactly 10 years. However, with electricity prices expected to continue rising, the real payback is likely to be shorter. If prices increase by just 3% per year, the payback drops to around 8.5 years.

After payback, the system will continue generating free electricity for another 15 years or more, with panels typically warranted for 25 years and batteries for 10 to 12 years.

Would they recommend it?

“Absolutely,” says Sarah. “It is one of the best investments we have made in our home. The bills are dramatically lower, we feel good about using clean energy, and the kids love watching the app to see how much electricity the panels are making.”

If you are in Lisburn or anywhere else in Northern Ireland and considering solar panels, comparing quotes from multiple installers is the best way to ensure you get a fair price. Use our free comparison tool to get up to three quotes from trusted local installers.