Contractor Budget Kit
Guides
Browse tools

SOLAR

Solar System Expansion Cost Calculator

Estimate the cost of adding capacity to an existing solar system.

JOB INPUTS

Enter your numbers

Loading saved values

Current installed capacity

Current installed capacity

Capacity you're adding

Capacity you're adding

Installed cost per peak watt

$
Installed cost per peak watt
Results update automatically
CALCULATED RESULTUSD
Expansion cost$10,500.00
Added capacity3 kW
New capacity11 kW
FORMULA USED3 kW × 1000 × $3.50 = $10,500.00

HOW TO USE IT

How to use the Solar System Expansion Cost Calculator

  1. 1

    Enter the current capacity in kW.

  2. 2

    Set the capacity to add.

  3. 3

    Enter the cost per watt.

  4. 4

    Review the expansion cost.

THE MATH

Solar expansion cost formula

Cost = added capacity (W) × cost/watt

Each added watt runs ~$3-3.50 in the US. The added capacity is converted to watts then multiplied by the cost.

PRACTICAL EXAMPLE

Current 8 kW, adding 3 kW at $3.50/W

Added = 3 × 1000 = 3,000 W. Cost = 3,000 × 3.50 = $10,500. New capacity = 11 kW.

FAQ

Frequently asked questions

How much does a solar expansion cost in 2026?

Nationally, $2.50-$3.50/W added, depending on size.

Can I expand with another panel?

Yes, if the inverter and roof space allow.

Do I need a new meter?

Often no, but check interconnection rules.