Grid-Tie Inverter Calculator

What size grid-tied inverter do you need? Enter your array and utility requirements — get sizing, DC:AC ratio, and clipping analysis.

Array & utility specs

Solar array size?

kW DC

System efficiency?

Utility interconnection?

Recommended inverter size

10.0 kW AC

Standard sizing (1.0 DC:AC)10.0 kW

Undersized option (1.25 DC:AC)8.0 kW (saves $200-400)

Clipping loss at 1.0 ratio0.0%

Estimated annual production14,125 kWh

Recommendation: For net metering, a 10.0 kW inverter matches your 10 kW array (1.0 DC:AC ratio). Slight undersizing to 8.0 kW (1.25 DC:AC) saves $200-400 with minimal clipping loss.

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How to Use This Calculator

Enter your array size

Enter your solar array's DC power in kW. This is the sum of all panel wattages divided by 1,000. For 25 × 400W panels, enter 10 kW. The system efficiency field (default 86%) accounts for real-world losses before AC output — adjusting this changes the clipping analysis.

Select your utility interconnection type

Choose from net metering (full export allowed), export limited (utility caps how much you send to grid), or no export (all solar consumed on-site). For export limited, enter your utility's cap in kW — found in your interconnection agreement. This directly affects the recommended inverter size.

Understand the sizing options

The result shows three sizing options: standard (1.0 DC:AC ratio), undersized (1.25 DC:AC), and the clipping loss for each. A 1.25 DC:AC ratio is common in the industry — slightly undersizing the inverter saves $200-400 with typically under 1-2% annual energy loss from clipping.

The Formula

Standard inverter kW = Array kW × 1.0 (1.0 DC:AC ratio) Undersized inverter = Array kW ÷ 1.25 (1.25 DC:AC ratio) Effective AC output = Array kW × System efficiency Clipping occurs when: Effective AC > Inverter rating Clipping % = (Effective AC - Inverter rating) ÷ Effective AC

Inverter clipping happens when the solar array produces more AC power than the inverter is rated for. The excess is simply not converted. Clipping is most significant in high-irradiance climates (desert southwest) and systems with high DC:AC ratios. A DC:AC ratio of 1.1-1.3 is widely accepted as optimal for US systems.

Example

10 kW array — standard net metering

Array size10 kW DC

System efficiency86%

UtilityNet metering (full export)

Sizing options

Standard (1.0 DC:AC)10 kW inverter, ~0% clipping

Undersized (1.25 DC:AC)8 kW inverter, ~1.5% annual clipping

Annual production~14,170 kWh/yr

The 8 kW inverter saves approximately $300 versus the 10 kW unit. At $0.15/kWh, the 1.5% clipping loss is about 213 kWh/yr = $32/yr lost. The inverter savings pays back in roughly 9 years — but since inverters typically need replacement after 10-15 years anyway, the undersized option is often the better financial choice. For cloudy climates with fewer high-irradiance hours, clipping is even less significant.

FAQ

What is a good DC:AC ratio for a grid-tied solar system? ▼

The optimal DC:AC ratio (also called the inverter loading ratio or ILR) is typically 1.1-1.3 for US systems. NREL studies suggest 1.2 is the sweet spot that minimizes total system cost while keeping clipping losses under 1-2% annually. Sunny climates (Arizona, Nevada) stay closer to 1.1 to limit clipping; cloudy climates (Pacific NW) can push to 1.3+ since high-irradiance hours are rare. Ratios above 1.5 are generally not recommended for grid-tied systems.

What happens if my inverter is too small for my array? ▼

When the array produces more AC than the inverter is rated for, the inverter simply limits (clips) its output to its rated power. It doesn't damage the inverter — this is normal operation. The excess solar energy that could have been converted is lost as heat in the panels (they operate at a slightly higher voltage). The trade-off is predictable and quantifiable: a slightly smaller inverter for a lower upfront cost, at the expense of some production on sunny peaks.

What is an export limit and why do utilities impose them? ▼

Some utilities limit how much solar power you can export to the grid to manage grid stability and transformer loading. Common limits: 3.68 kW (UK single-phase), 5 kW, 10 kW. When your system produces more than the export limit, the excess must be consumed on-site (by loads or batteries) or curtailed. Export-limiting inverters use a grid monitoring sensor to dynamically throttle output at the export cap. If your utility has an export limit, check the exact value in your interconnection agreement.

Do I need a larger inverter if I add battery storage later? ▼

Depends on the system architecture. A basic AC-coupled battery (like a Powerwall added to an existing solar system) uses its own separate inverter and doesn't affect your solar inverter size. A hybrid inverter (like SolarEdge HD-Wave or Solax) handles both solar and battery with one unit and must be sized for your solar array DC input and battery charge/discharge requirements simultaneously. If planning batteries from the start, consider a hybrid inverter sized for both.