Commercial & small business
Your inverter doesn't need to match your array's DC rating. See what AC capacity your system actually needs using a standard oversizing ratio.
How it works
Step 1
This comes from your solar system design or the system size by square footage tool if you're still in early planning.
Step 2
1.25 is a reasonable default for most commercial systems, though your installer may recommend a different ratio based on your specific site and climate. The interconnection cost estimator is also based on your final AC rating, so this step feeds directly into that one.
Step 3
Available inverter models come in specific size increments, so the final selection may round up slightly from this estimate. Check the three-phase system sizing tool if your site runs on three-phase power.
A 150 kW DC array at a standard 1.25 DC-to-AC ratio needs a 120 kW AC inverter. That ratio means the array's DC capacity exceeds the inverter's AC output capacity by design, which is standard commercial practice rather than a mistake in sizing. Once sized, the interconnection cost estimator covers the utility-side cost of connecting that inverter to the grid, and the underlying wiring requirements come from the National Electrical Code sections on interconnected systems, commonly referenced as NEC 690 and 705.
A solar array rarely produces its full rated DC output, since that peak only happens under ideal sun angle and temperature conditions for a small part of the day. Sizing the inverter below the array's DC rating, known as oversizing the DC side, captures more usable production during the many hours the array runs below peak, without needing a larger and more expensive inverter. The inverter itself is certified against IEEE 1547-2018, the performance standard that governs how it responds to grid abnormalities regardless of how it's sized, and the solar inverter size calculator in our inverters and equipment section walks through this same oversizing logic at a smaller scale.
Clipping happens on the rare occasions the array's DC output actually exceeds the inverter's AC capacity, at which point the inverter caps its output and the excess is lost. At a typical 1.25 ratio, clipping losses are usually small, often around 1 to 3% of annual production, a worthwhile tradeoff against the production gains from oversizing, similar to the shading-related losses covered in the solar shading analysis tool. The inverter clipping output loss calculator can help quantify the specific production loss at your chosen ratio.
Most commercial systems use a ratio between 1.15 and 1.35, with 1.25 being a common middle-ground choice. The right ratio for a specific project depends on local climate, panel orientation, and the specific financial tradeoff between inverter cost and clipping losses, which a system designer typically optimizes for the site. For three-phase installations, the three-phase system sizing tool covers additional considerations specific to that electrical setup, and the permitting cost estimator covers what getting the final design approved typically costs. Run the same inputs through solar inverter size calculator to cross-check this figure. If demand charges are a big part of your bill, the backup runtime estimator in our Battery & Storage section can show whether a battery would shave your peak enough to pay for itself.
Questions Roof condition decides a lot here. The roof inspection cost before solar estimator in our Solar + Roofing Integration section can help you check inspection and replacement costs before you size the system.
A 150 kW DC array at a standard 1.25 DC-to-AC ratio needs a 120 kW AC inverter. That ratio means the array's DC capacity exceeds the inverter's AC output capacity by design, which is standard commercial practice rather than a mistake in sizing.
A solar array rarely produces its full rated DC output, since that peak only happens under ideal sun angle and temperature conditions for a small part of the day. Sizing the inverter below the array's DC rating, known as oversizing the DC side, captures more usable production during the many hours the array runs below peak, without needing a larger and more expensive inverter.
Clipping happens on the rare occasions the array's DC output actually exceeds the inverter's AC capacity, at which point the inverter caps its output and the excess is lost. At a typical 1.25 ratio, clipping losses are usually small, often around 1 to 3% of annual production, a worthwhile tradeoff against the production gains from oversizing.
Most commercial systems use a ratio between 1.15 and 1.35, with 1.25 being a common middle-ground choice. The right ratio for a specific project depends on local climate, panel orientation, and the specific financial tradeoff between inverter cost and clipping losses, which a system designer typically optimizes for the site.