What size solar inverter do I need?

Your inverter capacity should match or slightly exceed your solar panel array's total wattage. For a 10,000W (10 kW) system, a 10 kW inverter is standard. Some installers size inverters at 90–110% of array size. String inverters handle a whole system; microinverters handle one panel each and work better with shading or complex roofs.

What's the difference between string inverters and microinverters?

String inverters are a single unit that handles the whole array — they're cheaper ($1,000–$2,000) but one shaded panel reduces output for the whole string. Microinverters attach to each panel individually ($150–$250/panel), maximizing output under shading and providing panel-level monitoring, but at higher overall cost.

What size inverter do I need for my solar system?

Your inverter capacity should be sized at 100–120% of your solar array's DC wattage. For an 8 kW solar array, a 7.6–10 kW inverter is appropriate. Slight oversizing (a higher DC:AC ratio up to 1.25:1) is common and allowed by most utilities — it improves energy harvest in low-light conditions without significantly exceeding the inverter's capacity on peak sunny days.

String inverter vs microinverter — which is better?

String inverters are more affordable ($800–1,500) but if one panel underperforms (due to shading or failure), it reduces the entire string's output. Microinverters ($100–200 per panel) optimize each panel independently — ideal for shaded or complex roofs. Microinverters cost $1,500–3,000 more for a typical system but offer better production, monitoring, and 25-year warranties.

Solar Inverter Size Calculator

Determine the right inverter size for your solar array. The inverter converts DC power from your panels to AC power for your home — proper sizing maximizes production while keeping costs efficient.

System Size (kW)

Efficiency (%)

About This Calculator

The Solar Inverter Size Calculator determines the appropriate AC capacity for your inverter based on your DC panel array size. Inverter sizing is one of the more nuanced decisions in solar system design — the goal is not to match inverter size exactly to panel capacity, but to deliberately undersize the inverter relative to the DC array. This practice, called "clipping" or "DC oversize," is standard in the industry because panels rarely hit their nameplate DC output under real-world conditions. An inverter sized at 80–90% of DC array capacity captures almost all real-world production while costing less than a perfectly matched inverter.

The standard DC:AC ratio (also called the inverter loading ratio or ILR) for residential systems is 1.10–1.25, meaning 8 kW of panels paired with a 6.4–7.3 kW inverter. At this ratio, the inverter "clips" peak DC output on only the sunniest midday hours — typically just 1–5% of annual production — while operating more efficiently throughout the rest of the day. Going above 1.25 DC:AC ratio increases clipping losses significantly and is generally not recommended. Below 1.10, you are paying for inverter capacity that rarely gets used.

Inverter efficiency (typically 96–99% for modern string inverters and 95–97% for microinverters) represents AC conversion losses. The best string inverters from SMA, SolarEdge, and Fronius achieve 98–99% peak efficiency. Microinverters (Enphase) and power optimizers (SolarEdge) offer per-panel optimization that improves production on shaded or mismatched roofs at some cost premium. For unshaded, uniform rooftop installations, high-efficiency string inverters typically offer the best value.

Inverter sizing is also critical for permit applications and utility interconnection agreements, which specify maximum inverter output in kW AC. Getting the inverter size right before submitting permits avoids costly change orders. Most residential inverters are priced between $0.10–0.20 per watt AC, so an 8 kW inverter costs roughly $800–$1,600 in equipment alone, with installation adding another $200–$500. The estimated cost shown here is equipment only.

Calculations based on NREL solar modeling data and industry-standard assumptions, built and maintained by the independent SolarToolsOnline research team.

Estimates only — not financial, tax, or legal advice. Verify important results with a licensed solar installer or financial professional before making decisions.