Energy Savings Payback Calculator | Annual kWh Cost & Simple Payback

Result

Formulas

$C_{\mathrm{existing}} = E_{\mathrm{existing}}\times r$
$C_{\mathrm{proposed}} = E_{\mathrm{proposed}}\times r$
$E_{\mathrm{saved}} = E_{\mathrm{existing}} - E_{\mathrm{proposed}}$
$C_{\mathrm{saved}} = E_{\mathrm{saved}}\times r$
$T_{\mathrm{payback}} = \frac{C_{\mathrm{project}}}{C_{\mathrm{saved}}}\quad\text{when }C_{\mathrm{saved}}>0$

An electrical efficiency upgrade must reduce annual energy cost enough to recover its installed project cost. The Energy Savings Payback Calculator produces the project’s simple payback in years by comparing existing annual energy use with proposed annual energy use at a stated electricity rate.

This calculation is commonly used to screen LED lighting retrofits, motor replacements, controls upgrades, HVAC electrical-load improvements, power-factor-related energy projects, and other electrical equipment changes. It supports early project budgeting and energy-use comparisons before a more detailed utility-bill review, load analysis, or financial evaluation.

The result is not an ampacity, voltage-drop, branch-circuit, feeder, conductor, raceway fill, or overcurrent-protection calculation. A project that has an acceptable energy payback may still require separate field review of circuit loading, conductor terminations, insulation temperature ratings, equipment listing, disconnecting means, and AHJ requirements.

Annual Energy Cost

The calculator uses four project inputs:

Input	Unit	Electrical purpose
Existing annual energy	kWh/year	Current annual electricity consumption for the equipment or system being replaced
Proposed annual energy	kWh/year	Expected annual electricity consumption after the project is complete
Electricity rate	$/kWh	Energy rate applied to both existing and proposed annual kWh
Project cost	$	Upfront project cost used for the simple-payback calculation

Existing annual energy and Proposed annual energy should represent equivalent operating conditions. For example, an LED retrofit comparison should use the same area, operating schedule, production demand, and expected annual run time for both systems.

The Electricity rate is entered in dollars per kilowatt-hour. A blended energy rate can be useful for preliminary screening when a facility has varying utility rates, but the rate should be selected deliberately. Demand charges, ratchets, time-of-use pricing, fuel adjustments, and other bill components are not separately modeled by this calculation.

Savings and Payback Formula

The calculator keeps the energy-savings arithmetic visible:

$\displaystyle \text{Existing annual cost} = \text{Existing annual energy} \times \text{Electricity rate}$

$\displaystyle \text{Proposed annual cost} = \text{Proposed annual energy} \times \text{Electricity rate}$

$\displaystyle \text{Annual kWh saved} = \text{Existing annual energy} - \text{Proposed annual energy}$

$\displaystyle \text{Annual cost saved} = \text{Existing annual cost} - \text{Proposed annual cost}$

$\displaystyle \text{Simple payback} = \frac{\text{Project cost}}{\text{Annual cost saved}}$

The calculator returns:

Existing annual cost in $/year
Proposed annual cost in $/year
Annual kWh saved in kWh/year
Annual cost saved in $/year
Simple payback in years

A lower simple-payback value indicates that annual electricity-cost savings recover the stated project cost sooner. If proposed energy use does not produce a positive annual cost savings, a normal positive simple-payback result is not available.

Calculation Example

For the entered values:

Input	Value
Existing annual energy	20,000 kWh/year
Proposed annual energy	15,000 kWh/year
Electricity rate	$0.15/kWh
Project cost	$5,000

The annual energy and cost results are:

$\displaystyle 20{,}000\ \text{kWh/year} \times $0.15/\text{kWh} = $3{,}000/\text{year}$

$\displaystyle 15{,}000\ \text{kWh/year} \times $0.15/\text{kWh} = $2{,}250/\text{year}$

$\displaystyle 20{,}000 - 15{,}000 = 5{,}000\ \text{kWh/year saved}$

$\displaystyle $3{,}000 - $2{,}250 = $750/\text{year saved}$

$\displaystyle \frac{$5{,}000}{$750/\text{year}} = 6.6667\ \text{years}$

The project reduces annual energy use by 5,000 kWh/year, reduces annual electricity cost by $750/year, and has a simple payback of 6.6667 years.

Electrical Project Boundaries

Simple payback evaluates energy savings against initial project cost. It does not determine whether existing electrical distribution equipment has adequate capacity or whether an altered installation complies with applicable electrical requirements.

Verify project conditions separately when they apply:

Lighting and equipment upgrades can change branch-circuit load, inrush characteristics, harmonic behavior, or control requirements even when annual kWh decreases.
Motor, HVAC, and process-equipment projects may affect feeder loading, disconnect sizing, overload protection, voltage drop, and available fault-current considerations.
New conductors or raceways require independent evaluation of AWG or kcmil conductor size, ampacity, correction factor, adjustment factor, current-carrying conductors, terminal rating, insulation temperature rating, raceway fill, and support methods.
Actual operating hours should be verified against schedules, controls sequences, production changes, and measured run time where practical.
Utility incentives, rebates, financing costs, tax treatment, maintenance savings, demand charges, and equipment-life differences are outside the calculator’s simple-payback arithmetic.

Use the result as an energy-cost screening number, then apply project-specific electrical design, field verification, manufacturer instructions, utility-billing review, and AHJ requirements before installation.