Sizing Solar Panels for an Irish Home

The right number of solar panels for an Irish home depends on when you use electricity, what your roof can generate and what happens to surplus power. Roof space sets an upper limit; it does not by itself establish the best system size.

Solar generation is concentrated in daylight hours. Electricity used directly at home is self-consumption; surplus can be stored or exported. Compare the value of avoided imports with your actual export tariff instead of assuming every generated unit has the same value. Batteries can shift energy into the evening but add cost and lose some energy in charging and discharging. ^[9]

Solar sizing checklist

1. Start with annual consumption. Gather 12 months of electricity use in kWh, not just the bill total. Ask an installer to model generation for your roof’s orientation, shading and condition. ^[2]
2. Check daytime demand. Note when the home is occupied and which loads can safely move into daylight hours. Compare expected self-consumption for a smaller and a larger system. ^[9]
3. Separate current use from future plans. Ask for a second scenario if you expect an electric vehicle, heat pump or another substantial load. State when that change would happen and when the equipment would run.
4. Compare storage options. Request quotations with and without a battery or hot-water diverter. Include storage losses and additional cost rather than assuming a battery always pays for itself. ^[9]
5. Verify export assumptions. Confirm the supplier’s current rate, eligibility, metering and grid-connection requirements. Request a sensitivity calculation with a lower export rate. ^[2]
6. Request comparable quotations. For each design, record panel capacity in kWp, annual generation in kWh, self-consumption, export, total price and maintenance assumptions. An annual estimate will not show whether supply matches demand hour by hour. ^[2]

A useful decision question: what do the extra panels add after allowing for electricity you can use, storage costs and realistically paid exports? Choose using that comparison, with an installer’s design for your home.

Would you also like to know how battery storage affects self-consumption and export?AskAnswer complete. One follow-up option available.