Annual Generation
3,600.00kWh
Annual Saving
€864.00
Payback
8.10 years
10yr Return
€1,640.00
Rates & sources
UK energy unit rates vary by region and supplier. Ofgem publishes a price cap refreshed each quarter.
Source: Ofgem — Energy price cap — figures refreshed at the start of each tax year.
When to use this calculator
- Before switching supplier, upgrading equipment, or comparing energy-saving changes.
- When you want to test different usage assumptions or price scenarios quickly.
- When you need a simple estimate before requesting installer or supplier quotes.
- When you are evaluating solar panels, a heat pump, or insulation and want to check the payback period before spending.
- When your tariff is about to change and you want to quickly model the impact on your annual energy bill.
A realistic Ireland planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
System Size (kWp)
4.5 kW
Installation Cost (€)
€7,500
Peak Sun Hours Per Year
25 years
Electricity Price (€/kWh)
4.5 kW
After entering these figures, review annual generation, annual saving and payback together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Annual Generation
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Annual Saving
This gives you the recurring yearly benefit of the change or upgrade, which is usually the most practical starting point when comparing options. Divide it by 12 to see the monthly equivalent, or multiply by 5 to get a five-year view of the cumulative gain.
Payback
The payback period shows how many months or years it takes to recover the upfront cost through ongoing savings or income. Compare it against how long you plan to stay in the property or use the product before deciding whether the investment makes financial sense.
10yr Return
Use this to compare scenarios over different time horizons and judge whether the projected outcome clears your minimum required target. Remember that real-world returns fluctuate, so also check the result under a more conservative growth assumption.
Method & assumptionsAuthoritative sources
This calculator estimates the financial return from a domestic solar panel installation by modelling three income streams: electricity you generate and use directly (avoiding grid purchases at your unit rate), electricity you export under the Smart Export Guarantee (paid at your entered SEG rate), and any applicable government incentives. It assumes a panel output figure based on the system size you enter, adjusted for typical UK irradiation levels for a south-facing roof. East- or west-facing installations produce roughly 15–20% less annually. The calculator does not account for panel degradation over time, which averages around 0.5% per year for quality panels, nor does it model battery storage independently. Installation costs vary considerably by region and installer, so obtaining at least three quotes is advisable before using this tool for budgeting purposes.
Common mistakes
- !Using optimistic assumptions without testing a more cautious scenario as well.
- !Comparing outputs from different tools without checking that the inputs match.
- !Treating the result as a final quote instead of a planning estimate.
- !Using the current tariff rate without accounting for future price changes, which can make payback calculations look more favourable than they really are.
- !Forgetting to include the standing charge when comparing annual energy costs, which can be a significant portion of a typical bill.
What to do next
- Run the same scenario with a 10% higher unit rate to see how your figures would look if prices rise.
- Compare this result with a related energy or insulation calculator before requesting installer quotes.
- Use the linked guides to understand export tariffs, grant eligibility, or supplier comparison approaches.
- If you are evaluating an upgrade, get at least two installer quotes and rerun this calculator with the actual cost figures before committing.
- Set a reminder to rerun the calculation when your tariff renews, so the payback estimate stays accurate.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.
End-of-article next steps
Where to go after this calculator
Move to a focused hub instead of restarting your research from scratch.
Best Tools for Small Business
Pick software, validate unit economics, and execute workflows with one connected path.
Open hub →
Startup Resource Center
A startup stack for software decisions, runway math, and practical launch workflows.
Open hub →
Creator Toolkit
Choose creator platforms, calculate revenue targets, and ship assets faster.
Open hub →
Money Management Tools
A practical path for financial product choices, scenario math, and planning utilities.
Open hub →