Why oversize solar panels?
Why oversizing your solar panels makes sense in Ireland
When we design solar systems, we don't follow a one-size-fits-all rule. Every home is different, and so is the weather. That's why you'll often see us recommend more panels than you might expect. It's not about overselling - it's about making sure your system performs well all year, especially in Ireland's less-than-sunny climate.
5 reasons to oversize solar panels
We often get asked why we fit more panels than the inverter seems to support. It's a good question. Here's the straightforward answer.
- 1. You can only export up to 5kW of AC power to the grid due to ESB regulations. This is the limit for residential systems, regardless of how much your panels can generate.
- 2. Inverters often accept more power from the panels (DC) than they can output to the home or grid (AC). This means we can install more panels than the inverter's rated output, without overloading it.
- 3. Ireland doesn't get the kind of sunshine needed to regularly push your panels to their full rated output. The extra capacity helps balance this out over the year.
- 4. On cloudy or short winter days, the extra panels work harder to make the most of available light. That means better overall performance when conditions aren't ideal.
- 5. Clipping happens when your panels generate more power than the inverter can handle. The system simply trims the excess. This only tends to happen for a few hours on very sunny summer days, and the gain across the rest of the year far outweighs that small loss.
Understanding peak performance
Each solar panel has a peak power rating. That's the number you see like 435Wp or 440Wp. But these ratings come from lab conditions you just don't get in Ireland.
Standard test conditions (STC)
- 25°C temperature
- 1000 watts per square metre of solar radiation
- 1.5 air mass
These conditions rarely line up in Ireland. What we do get is cooler weather, which helps panels operate more efficiently.
What you actually get from your solar panels
A panel rated at 440 watts will not give you 440 watts all the time. Under typical Irish conditions, output might be closer to 327 watts per panel. That's what the datasheets call the 'Nominal Operating Cell Temperature' performance.
With a 7.83kW system, you might get about 5.89kW on an average day. And that's a good match for a 5kW inverter.
In summer you might lose a little at peak times due to clipping, but in winter you gain far more by having those extra panels pulling in whatever light is available. If you really feel like nerding out on your solar panel specs check out the Jinko solar panel datasheet below.
Environmental factors matter
Solar panels are affected by a lot of things, including:
- Panels stay cleaner in Ireland thanks to rain
- Hot days don't always mean high output - panels need the right kind of radiation, not just heat
- In winter, the Earth is farther from the sun and radiation is lower
All this means that panels won't hit their top rated output most of the time, and that's expected. Oversizing helps smooth out the ups and downs.
The bottom line
Oversizing your system doesn't mean waste. It means getting more consistent performance year-round. And in Ireland, that's exactly what you want. It's not about selling more panels. It's about designing the best solar system that works for you, in real world conditions. That's what we care about.
Need a hand?
If you still have questions around oversizing your solar panels get in touch with your installation team at PureVolt.ie and we will be happy to help.