Solar Energy Cost Calculator

A solar energy cost calculation converts an installed solar system’s capital cost and expected operating cost into a cost per kilowatt-hour. The primary result is Levelized cost, expressed in $/kWh. It provides a simple lifetime cost benchmark for comparing a proposed solar array with utility energy charges, another generation option, or alternative system designs.

For electrical design and project screening, the result can help compare the economic effect of design choices that change installed cost or production. Examples include conductor routing, DC and AC feeder lengths, raceway layout, inverter selection, module count, service capacity constraints, and expected annual kWh output. A longer conductor run may increase material and labor cost; voltage-drop limits, inverter operating voltage, ampacity, raceway fill, equipment layout, and actual production conditions still require separate engineering and field review.

The calculation uses four inputs:

Input	Unit	Purpose
System cost	$	Installed or assumed solar system cost
Annual energy	kWh/year	Expected annual energy output
Annual O&M cost	$/year	Annual operation and maintenance allowance
Lifetime	years	Assumed project operating life

Lifetime Energy

Annual energy is the assumed first-year or representative yearly solar production used by the calculation. The calculation applies the same annual kWh value for every year of the stated Lifetime.

\(\displaystyle \text{Lifetime energy} = \text{Annual energy} \times \text{Lifetime}\)

The result is shown in kWh.

For example, 24,000 kWh/year over 25 years produces:

\(\displaystyle 24{,}000 \text{ kWh/year} \times 25 \text{ years} = 600{,}000 \text{ kWh}\)

This is a constant-output assumption. Actual PV production can be affected by module degradation, shading, soiling, inverter availability, temperature, orientation, weather variability, curtailment, and changes in site conditions. Those effects are outside this calculation.

Lifetime Total Cost

The Lifetime total cost combines the initial System cost with the recurring Annual O&M cost across the selected lifetime.

\(\displaystyle \text{Lifetime total cost} = \text{System cost} + (\text{Annual O\&M cost} \times \text{Lifetime})\)

For an $18,000 system with $250/year in O&M over 25 years:

\(\displaystyle 18{,}000\text{ USD} + (250\text{ USD/year} \times 25\text{ years}) = 24{,}250\text{ USD}\)

The calculation treats all dollars equally regardless of when they occur. It does not discount future O&M expense, model loan payments, account for interest, or calculate an after-tax project return.

Levelized Cost

Levelized cost divides lifetime total cost by lifetime energy:

\(\displaystyle \text{Levelized cost} = \frac{\text{Lifetime total cost}} {\text{Lifetime energy}}\)

Using the example values:

\(\displaystyle \frac{24{,}250\text{ USD}}{600{,}000\text{ kWh}} = 0.0404\text{ USD/kWh}\)

The calculated solar energy cost is therefore 0.0404 $/kWh, or approximately 4.04 cents per kWh.

This value is a lifetime average cost of solar energy under the entered assumptions. It is not the utility bill savings rate. A utility tariff may include separate energy, demand, delivery, fixed, time-of-use, export-credit, and minimum-bill components. Solar production may offset those charges differently depending on the service rate and interconnection arrangement.

Annualized and Capital Cost Results

The result panel also includes two supporting values.

\(\displaystyle \text{Annualized total cost} = \frac{\text{Lifetime total cost}} {\text{Lifetime}}\)

\(\displaystyle \text{Capital cost per kWh} = \frac{\text{System cost}} {\text{Lifetime energy}}\)

For the stated example:

Result	Calculation	Value
Lifetime energy	24,000 kWh/year × 25 years	600,000 kWh
Lifetime total cost	$18,000 + ($250/year × 25 years)	$24,250
Levelized cost	$24,250 ÷ 600,000 kWh	0.0404 $/kWh
Annualized total cost	$24,250 ÷ 25 years	970 $/year
Capital cost per kWh	$18,000 ÷ 600,000 kWh	0.03 $/kWh

Annualized total cost spreads the undiscounted lifetime cost evenly over the assumed operating years. It is useful for high-level comparison against expected annual energy value, but it is not an accounting depreciation schedule or a financing payment.

Capital cost per kWh isolates the installed system cost from recurring O&M. In the example, the $18,000 system cost contributes 3 cents per lifetime kWh, while O&M accounts for the remaining approximately 1.04 cents per kWh.

Electrical Design Relationship

Solar energy cost is affected by electrical design decisions, but it does not replace electrical design calculations.

PV source circuits, output circuits, feeders, and interconnection conductors must be selected using the applicable electrical requirements and actual installation conditions. Conductor ampacity may depend on AWG or kcmil size, insulation temperature rating, terminal rating, ambient-temperature correction factor, adjustment factor for current-carrying conductors, raceway conditions, and equipment listing. Voltage-drop review may affect conductor size and installed cost, particularly where an array, combiner, inverter, disconnecting means, distribution equipment, or point of interconnection is separated by a long run.

A lower-cost conductor or raceway path should not be selected solely because it reduces the calculated cost per kWh. The design must separately verify ampacity, overcurrent protection, disconnecting means, grounding and bonding, inverter requirements, equipment ratings, utility interconnection requirements, installation instructions, and AHJ approval.

Calculation Boundary

The estimate is an undiscounted lifetime solar cost review from System cost, Annual energy, Annual O&M cost, and Lifetime. It does not include incentives, financing, inflation, utility escalation, taxes, insurance, module degradation, replacement equipment, inverter replacement, production risk, demand-charge effects, export compensation, or a site-specific production study.