How is simple payback calculated?

Simple payback is the project cost divided by the annual money saved. A 2,000 unit LED retrofit that saves 800 units a year pays back in 2.5 years. It ignores interest and rising energy prices, so it is a conservative first-pass screen for an investment case.

What efficiency figures do motors and HVAC use?

For a motor or compressor, savings come from the same mechanical output delivered at higher efficiency: old kW input minus new kW input. For HVAC, improving the coefficient of performance (COP) or SEER reduces the electrical input needed for the same heating or cooling output.

How accurate is the kWh saved figure?

It is as accurate as your inputs. The arithmetic is exact, but real savings depend on actual run hours, load profiles, and weather. Use measured baseline data where possible and treat the result as a planning estimate, not a guaranteed bill reduction.

Why include CO2 savings?

Many efficiency projects are now justified partly on carbon, not just cost. Multiplying kWh saved by your grid's carbon intensity in grams CO2e per kWh shows the emissions avoided, which supports net-zero reporting and ESG disclosures alongside the financial case.

Does lighting use a different model?

Lighting savings are the difference between old and new fixture wattage, multiplied by the number of fixtures and annual burn hours. A 36 watt fluorescent replaced by an 18 watt LED across 100 fixtures running 3,000 hours saves 5,400 kWh a year.

Energy Efficiency kWh Savings Estimator

Energy efficiency upgrades only get funded when the savings are quantified. This estimator takes a baseline and an improved case for five common upgrade types and computes the annual kWh saved, the money that translates to, the simple payback against your capital cost, and the CO2 emissions avoided — everything an energy manager needs for a one-page investment case.

How it works

All five upgrade types reduce to the same core idea — power saved multiplied by operating hours — but the way you derive the power difference varies:

Lighting:   kW saved = (old W − new W) × fixtures / 1000
Motor/comp: kW saved = old input kW − new input kW
HVAC:       new input kW = output kW / new COP
            kW saved     = (output / old COP) − (output / new COP)
Fabric:     kW saved entered directly as avoided demand

annual kWh saved = kW saved × annual hours
annual money     = kWh saved × electricity price
payback (years)  = project cost / annual money
CO2e avoided (kg)= kWh saved × carbon g/kWh / 1000

For HVAC, a higher coefficient of performance means less electricity is needed to move the same amount of heat, so the saving grows as the gap between the old and new COP widens.

Example and tips

Replacing 100 fixtures of 36 W fluorescent with 18 W LED, running 3,000 hours a year at 0.20 per kWh, saves 5,400 kWh and 1,080 in energy a year; a 2,000 project pays back in under two years and avoids roughly 1.35 tonnes of CO2e on a 250 g/kWh grid. Always base the annual-hours figure on real operating schedules — overstating run time is the most common way efficiency business cases disappoint in practice.