Choosing solar panels and inverters without the jargon
Why equipment choice matters less than you think
Most modern panels from established manufacturers perform within a few percent of each other. The quality of the design and installation usually has a bigger effect on your results than the brand on the label. Still, a few specifications are worth understanding so you can compare quotes fairly.
Solar panels: the specs that matter
Power rating
Measured in watts (W). Residential panels today are typically 400 to 450 W. A higher rating means fewer panels for the same system size, which helps on small or awkward roofs.
Efficiency
The share of sunlight a panel turns into electricity, usually 20 to 23 percent. Higher efficiency matters when roof space is limited. If you have plenty of space, a slightly less efficient panel at a lower price can be the better deal.
Temperature coefficient
Panels lose output as they heat up. The temperature coefficient tells you how much, as a percentage per degree. A value closer to zero, such as -0.30 %/°C, performs better in hot climates.
Warranties
Look for two separate warranties:
- Product warranty: covers defects in materials and workmanship, commonly 15 to 25 years
- Performance warranty: guarantees a minimum output after a set period, often around 85 to 90 percent after 25 or 30 years
A warranty is only as good as the company behind it. Ask how claims are handled and who covers labour if a panel needs replacing.
Inverters: three main options
The inverter turns the direct current from your panels into the alternating current your home uses. It is the part most likely to need replacing during the life of a system, so it deserves attention.
| Type | How it works | Best for | Watch out for |
|---|---|---|---|
| String inverter | One central unit for a row of panels | Simple, unshaded roofs | Shade on one panel lowers the whole string |
| String with optimisers | Central unit plus a small device on each panel | Partial shade, several roof faces | More parts on the roof |
| Microinverters | A small inverter behind each panel | Complex roofs, panel-level monitoring | Higher upfront cost |
Hybrid inverters
A hybrid inverter can manage a battery as well as panels. If you aren’t adding storage now but might later, a battery-ready hybrid avoids replacing the inverter in a few years.
Specs you can mostly ignore
- Maximum efficiency of the inverter: nearly all are above 96 percent; the difference is tiny
- Panel colour and frame finish: a matter of looks, not output
- Peak output claims in marketing: compare tested ratings on the datasheet instead
Questions to ask when comparing quotes
- Which panel and inverter models are included, with datasheets?
- Is the system designed around shade on any part of the roof?
- What is the inverter warranty, and can it be extended?
- Is the inverter battery-ready?
- How will I monitor the system, and does monitoring show each panel?
- Who do I call if something stops working?
The bottom line
Choose a reputable installer first, then let them recommend equipment suited to your roof. A well-designed string system can outperform a poorly planned premium one. Focus on warranties, shade handling, and future plans such as storage, and you’ll make a choice that serves you for decades.
