Solar savings calculator
Estimate what generated electricity may be worth when part is used at home and the rest is exported.
What self-consumption means
Self-consumed solar is electricity generated by your system and used in the building rather than exported. Each self-consumed kWh can avoid buying roughly one kWh at your import tariff, subject to the way your tariff is structured.
What this calculator does not model
It does not model financing, panel degradation, maintenance, taxes, battery losses or hour-by-hour tariff changes. It is a simple annual-value estimate designed for first-pass comparisons.
How to read the number this calculator gives you
Solar self-consumption savings are one of the harder household energy figures to estimate accurately, because the value of a solar panel system depends not just on how much electricity it generates but on how much of that generation is actually used inside the home at the moment it is produced, versus exported to the grid at a lower rate. This calculator focuses on the self-consumption portion — the share of solar output that directly offsets electricity you would otherwise have bought from your supplier at full retail price. That offset is usually the most valuable part of a home solar system, which is why installers and energy advisors typically encourage shifting flexible loads, such as washing machines, dishwashers or EV charging, into daylight hours to raise the self-consumption share.
Why this is an estimate, not a quote
Actual savings depend on your system's real generation profile across the seasons, your household's hour-by-hour usage pattern, any battery storage that shifts self-consumption into the evening, and your specific export tariff if you sell surplus back to the grid. A rooftop system in northern Europe will generate a very different seasonal curve to one in southern Spain or Italy, and a household that is out at work all day will self-consume a smaller share of midday generation than one with someone home. Treat the result as a planning estimate to sense-check quotes and payback assumptions, not as a guaranteed figure.
Example self-consumption scenarios
| System size | Self-consumption share | Approx. annual saving* |
|---|---|---|
| 3 kWp, no battery | 30% | €150–€250 |
| 4 kWp, no battery | 35% | €230–€350 |
| 4 kWp with home battery | 55–65% | €380–€550 |
| 6 kWp with battery and EV charging shifted to daytime | 65–75% | €600–€850 |
*Illustrative ranges at a typical €0.30/kWh retail price; actual savings depend on location, system output and household usage pattern.
Frequently asked questions
Does adding a battery always increase savings?
Usually yes, because a battery lets you store midday surplus generation and use it in the evening instead of exporting it at a lower rate, raising your effective self-consumption share. The extra savings need to be weighed against the battery's own cost.
Why is exported electricity worth less than electricity I use myself?
Export or feed-in tariffs are typically well below the retail price you pay for imported electricity, so every kWh you consume directly from your own panels is worth more than one you sell back to the grid.
What self-consumption percentage is realistic without a battery?
Many unshaded residential systems without storage self-consume roughly 25–40% of their generation, depending heavily on how much of the household's usage happens during daylight hours.
Does this calculator account for seasonal variation in sunlight?
Not directly — it works from an annual generation and self-consumption estimate you provide. For a seasonally accurate figure, use monthly generation data from your installer's estimate or an existing system's monitoring app.
Should I use gross or net electricity price in the price field?
Use your normal retail unit price per kWh, since that is the cost every self-consumed kWh is actually offsetting on your bill.
