Solar Payback Calculator

How Solar Payback works

The stated formula is payback = cost ÷ annual savings. Solar Payback uses Installed cost, Annual savings to report Simple payback. Use Solar Array Configuration Calculator to a separate total modules calculation.

In the loaded Solar Payback case, simple payback equals 8.75 years. A second case makes the effect of one changed measurement visible.

Use a measured Installed cost range in Solar Payback. The loaded value is 14,000 $; a separate case at 11,900 $ changes simple payback from 8.75 years to 7.44 years. Solar Payback holds annual savings against installed cost.

For Solar Electricity, test Simple payback at nominal and limiting installed cost values. Keep the Solar Payback cases separate.

Inputs for Solar Payback

Installed cost and Annual savings belong to Solar Payback. Keep source units with installed cost.

No recommendation is implied by the loaded example. Use measurements from the intended scenario.

Installed cost

Example entry: 14000 $.

Annual savings

Example entry: 1600 $/year.

When Solar Payback feeds another worksheet, transfer Simple payback at full precision. Preserve cold voltage, hot operating voltage, controller limits, energy yield, and shading loss. Round installed cost after the Solar Payback transfer.

Convert Installed cost for Solar Payback. Store original and converted installed cost values for Solar Payback. Prefix errors alter simple payback.

Reading the Solar Payback result

This output represents Solar Payback.

The result informs selection but does not approve a component or installation.

Use Simple payback to use Solar Payback to calculate simple payback. Compare it with cold voltage, hot operating voltage, controller limits, energy yield, and shading loss. Simple payback does not override another Solar Electricity limit.

For Solar Payback, preserve Installed cost and simple payback under the same irradiance, cell temperature, season, orientation, and string configuration record before final use.

Measurement and units

Use site-specific irradiance, temperature, shading, equipment limits, and measured system losses. Check prefixes on installed cost.

Preserve the measurement basis when testing alternatives.

For Solar Payback, source Installed cost from module datasheets, site measurements, weather records, and inverter logs. Record irradiance, cell temperature, season, orientation, and string configuration. Annual savings needs matching conditions.

Limits of this calculation

Financing, maintenance, degradation, and tariff changes are omitted. Use Solar DC Cable Loss Calculator.

Treat the formula as one part of the overall electrical analysis. Unentered effects remain outside Solar Payback.

Evaluate weather variability, mismatch, clipping, soiling, degradation, and curtailment separately. In Solar Payback, represent each effect through Installed cost. Document installed cost allowances.

Records for Solar Payback

In Solar Payback, tie installed cost to its source and state. Continue to Off-Grid Solar Array Calculator for required array size.

Preserve raw simple payback with the chosen installed cost rating.

For Solar Payback, record installed cost, annual savings. Record Installed cost state for Solar Payback. Keep simple payback unrounded.

Questions about Solar Payback