What’s the calculator useful for?

This calculator gives a reasonable first approximation of the cost of a solar panel installation in Ireland. It’s useful if you’re in the early stages of considering a solar panel installation and want to know if it’s something that would be generally viable for you before seeking firm quotes. Firm quotes can vary from the estimate above depending on the details of your roof, whether you are offered budget or premium hardware, and many other factors.

How much will solar panels save me?

For a very rough guide, you can assume savings of about €200 per year per kilowatt of solar panels installed. So, for example, you could expect to save very roughly €1,000 per year with a 5 kW solar panel installation.

However, for a much more accurate estimate, which also factors in the savings from a battery (if you choose to include one), use the Kilowatt.ie electricity price comparison tool. This lets you factor in your real electricity usage profile via smart meter data and run a detailed simulation for each half-hour period across a whole year, to get a much more accurate picture of how much you could save with solar.

Savings could go up or down in the future depending on changes to energy prices, taxes, and other factors. In general though, having solar panels installed reduces your exposure to energy price swings.

Also, if you have a mortgage, you may want to take into account the impact that installing solar could have on your Building Energy Rating. A better BER grade can unlock access to green mortgages for many homes, meaning many thousands of euros in mortgage interest savings on top of the lower electricity bills.

How many panels should I install?

It’s generally best to install as many panels as possible, until you hit one of these limits:

• As many as you can fit on the roof
• Around 11 kW of panels

The 11 kW number is not an exact figure, but it’s about the most that realistically makes sense for Irish households given ESB Networks limits on the size of inverter that you can install without special (NC7) permission.

Perhaps surprisingly, this rule holds true even for households with low electricity usage: Even if you have already gone far beyond covering your own needs, each additional solar panel can still pay you well in terms of surplus electricity that you can sell to the grid.

Is a battery worthwhile?

If you have medium or high usage, then a battery can pay for itself, but perhaps not in the way that you think. Rather than using the battery to store surplus solar energy for use overnight, what make most sense in Ireland currently is to charge the battery using discounted night-rate electricity. This stored low-cost electricity can then be used to power the home during the day, while any high-value surplus solar electricity can be exported to the grid.

The exact calculations get complicated quickly, so it’s best to use our electricity price comparison tool, to see how much a battery could save you, give your own unique circumstances.

In general, batteries can provide a decent return on investment, but generally not as dramatic as solar panels. So if you have a tight budget then prioritise panels but consider including a “hybrid” (battery-ready) inverter so that you can add batteries at a later date.

How about a hot water power diverter?

Hot water power diverters don’t make much sense given the current state of the Irish electricity market. Right now, it generally makes more sense to run your immersion using cheap night/EV rate electricity, and export your surplus solar energy for a higher profit, than to “waste” that valuable daytime electricity running an immersion heater.

However, a simple timer switch which allows you run your immersion each night using discounted off-peak electricity can make a lot of sense.