Blog Article
Thinking of pairing a battery with your solar panels? Choosing the right size battery can make or break your system’s efficiency and savings. Let’s walk through how to get it right
What to Know First
(Capacity, Usable Energy & Depth of Discharge)
When shopping for a solar battery, you’ll see terms like total capacity, usable energy, and depth of discharge. Here’s what they mean and why they matter
- Total Energy Capacity (kWh): This is the maximum energy the battery can store, what the manufacturer advertises.
- Usable Energy Capacity (kWh): This is how much of that stored energy you can actually use, often a bit lower to protect battery life.
- Depth of Discharge (DoD): This expresses the safe percentage of the total capacity that can be used regularly. Many modern batteries allow 90 % DoD for balance between usability and longevity.
In short: usable energy is more important for your day-to-day needs than the total headline capacity.
Typical Battery Sizes & What They Suit
In Ireland, many homes start in the 5 kWh range for battery capacity. That’s a solid starting point for average usage. But depending on your setup, you might go lower (for smaller homes) or much higher (for bigger households or high usage). As battery tech improves, you’ll find more flexibility, modular systems, scalable units, etc.
What Factors Should You Consider?
To choose a battery size that fits you, consider:
- Usable Capacity - how much you’ll actually draw
- Power Rating - how many appliances you might run at once
- Solar PV Size - your panel output influences how much energy you can fill the battery
- Electricity Usage Patterns - when do you use power? Evening, night, weekends?
- Electricity Prices / Tariffs - can you charge cheaply or get some benefit from exporting?
- Battery Usage Goals - full backup, partial, or daily cycling?
What About Household Usage in Ireland?
On average, Irish homes use 4,200 kWh per year, that’s about 11.5 kWh per day. But winter, lifestyle, heating, EV charging, all that can push it higher or lower. Let’s say your solar panels produce 10 kWh a day. Depending on how much you shift your usage to after sunset, you might pair that with a 4–8 kWh battery, or more if you want days of autonomy.
Example Scenario
- Daily usage: 11.5 kWh
- Solar production: 9 kWh (on average)
- If you aim to cover your evening and night usage, a 6–8 kWh usable battery might be a sweet spot.
- Want backup for 1–2 cloudy days? Then scale up accordingly.
Choosing the Right Battery Size
- Focus on usable capacity, not just what’s advertised
- Use real figures (your usage, your system output)
- Don’t oversize unnecessarily, under-charged batteries waste cost.
- Always consider future needs (e.g. EVs, heat pumps)
Ready to find the perfect solar battery for your home? Talk to our expert team at New Energy, we’ll help you size your system, unlock SEAI grants, and start saving from day one.
