ClueLumaEnergy calculators
447 free calculators for energy managers and engineers: utility bills, economics, motors, lighting, HVAC, steam, compressed air, renewables, storage and M&V. Fill in what you know and leave one box empty; each calculator solves for it, shows the formula typeset like a textbook, and walks through a worked example.
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Unit converters 7
M&V data tools 2
Economics and life-cycle cost 44
- Net annual savings
- Simple payback (SPP)
- Simple interest amount
- Simple interest future amount
- Single sum F/P
- Single sum P/F
- Uniform series F/A
- Uniform series A/F
- Uniform series A/P
- Uniform series P/A
- Arithmetic gradient P/G
- Arithmetic gradient A/G
- Net present worth (NPW)
- Net future worth (NFW)
- Net annual worth (NAW)
- Benefit/Cost Ratio (BCR)
- MACRS depreciation
- Income tax calculation
- Market, inflation and real rates
- Current to constant dollars
- Constant to current dollars
- Escalated energy cost
- Net initial investment
- Depreciation tax shield
- Straight-line depreciation
- Undepreciated asset basis (BV)
- Tax-adjusted operating savings (AT)
- Principal portion of payment
- Uniform-cost life cycle cost (LCC)
- First-year net cash saving
- After-tax salvage
- Discounted escalated future cost
- Annual worth after capital recovery (AW)
- Two-period nonuniform net present worth (NPW)
- Effective annual interest
- Deferred uniform present worth
- Beginning-period uniform present worth
- Base plus gradient annual equivalent
- Initial plus annual accumulation
- Unfinanced operating after-tax cash flow (ATCF)
- Present worth with midlife replacement (NPW)
- Operating hours required by a payback limit
- Price escalation at a future budget limit
- Present worth of escalating annual savings (PW)
Utility bills and rates 26
- Total electricity bill
- Average interval demand
- Energy at constant power
- TOU energy charge
- Ratchet billing demand
- Demand charge
- Future ratchet excess
- Power factor (PF)
- Apparent power
- PF-adjusted demand
- Taxed bill
- Average electricity cost
- Avoided electricity cost
- Two-block energy charge
- TOU shifting saving
- Useful fuel heat price
- Contract minimum billing demand
- Water and sewer charge
- Weighted contracted gas price
- Separately metered water and sewer cost
- Avoided cost of lossy load shifting
- Reactive demand at a fee limit
- Net annual curtailment-service benefit
- Annual energy at a supplier cost crossover
- On-peak runtime within an energy-cost limit
- Minimum power factor for compensation cost recovery
Electrical power and motors 45
- Ohm's law
- DC and resistive AC power
- Resistance power and I²R loss
- Balanced wye voltage
- Power triangle
- Power factor (PF)
- Single-phase real power
- Balanced 3-phase real power
- Correction factor from the power triangle
- Facility monthly electric load factor (FMELF)
- Billing period hours
- Average energy cost
- Demand reduction cost saving
- Wye line-to-neutral voltage
- Reactive power from real and apparent power
- Real power from apparent power and PF
- Balanced three-phase line current
- Balanced three-phase apparent power
- Capacitor reactive compensation
- Peak demand from load factor
- Conductor loss reduction
- Additional reactive compensation
- Line voltage from balanced real power
- Power factor after a partial capacitor bank
- Reactive compensation for a feeder-current limit
- True power factor with harmonic current
- Neutral heating from in-phase triplen currents
- Synchronous speed
- Motor slip speed
- Motor efficiency
- Power factor (PF)
- Motor load factor (LF)
- 3-phase real power
- Input from nameplate and load
- General motor power savings
- Same-load efficiency savings
- Motor annual electric cost or savings
- Simple payback (SPP)
- Motor project ROR
- Flow versus speed
- Head versus speed
- Power versus speed
- Mechanical shaft output from electrical input
- Energy over a motor duty profile
- Speed for a friction-dominated head target
Lighting 31
- Luminous efficacy
- T-number lamp diameter
- Ballast-factor output
- Coefficient of utilization (CU)
- Spot replacement cost
- Group replacement cost
- Fixture input power
- Retrofit demand reduction
- Annual lighting energy savings
- Energy cost savings
- Annual demand cost savings
- Annual lamp replacements
- Annual lamp cost change
- Relamping labor savings
- Cooling electricity savings
- Added heating gas cost
- Total annual net savings
- Installed cost and simple payback (SPP)
- Lighting project rate of return
- Lighting benefit/cost ratio (B/C)
- Control schedule savings
- Maintained average illuminance
- Point-source illuminance
- Room cavity ratio (RCR)
- Combined light-loss factor (LLF)
- Required lumen-method fixture count
- Lighting power density (LPD)
- Point-source intensity for a target illuminance
- Lighting plus induced cooling energy savings
- Group-relamping interval threshold
- Fixture cost at discounted break-even
HVAC and building envelope 56
- Relative-humidity approximation (RH)
- Breathing-zone outdoor air
- Airflow per person
- Energy efficiency ratio from energy (EER)
- Energy efficiency ratio from capacity (EER)
- Coefficient of performance (COP)
- Input power per cooling ton
- COP and EER relationship
- KW/ton from EER
- KW/ton from COP
- General sensible heat transfer
- Standard-air sensible heat
- Liquid-water sensible heat
- Annual conduction by degree days
- Motor average electrical use
- Equipment heat from kW
- Single-phase equipment heat
- 3-phase equipment heat
- Lighting heat in the space
- Cooling saving from reduced lighting
- Ventilation fan cube law
- Fan motor saving at equal efficiency
- Fan motor saving at differing efficiency
- Air total heat rate
- Air latent heat rate
- Adiabatic air mixing enthalpy
- Cooling-tower range
- Cooling-tower approach
- Total coil capacity
- Condenser heat rejection
- Sensible heat ratio (SHR)
- Steady envelope conduction
- Glazing admitted solar heat
- Required sensible airflow (CFM)
- Mixed-air humidity ratio
- Required water flow (GPM)
- Leaving enthalpy for a total coil load
- Usable recovered condenser heat
- Opaque-wall resistance within a shared heat limit
- Ventilation-limited minimum supply fraction
- Outdoor fraction from mixed-air temperatures
- Conduction heat flux
- Material resistance
- Conductance and overall U
- Heat flux
- Total heat-transfer rate
- Tank side-and-top area
- Heat-loss reduction and percentage
- Equivalent pipe-insulation thickness
- Equivalent pipe resistance
- Pipe surface area per length (A/L)
- Remaining-layer equilibrium
- Heating-degree-day cost
- Cooling-degree-day cost
- Insulation mean temperature
- Annual cost of a stated useful heating rate
Boilers and steam 30
- Useful annual fuel heat
- Supplemental fuel required
- Mass-based annual cost or receipt
- Fuel heat-input rate
- Fuel ton/day to lb/h
- Condensate sensible heat return
- Radiation-loss estimate
- Convection-loss estimate
- Heat carried by a mass stream
- Net steam-generation heat
- Boiler heat-balance closure
- Useful boiler efficiency
- Fuel input for target steam load
- Two-fuel ash production
- Boiler fuel saving fraction
- Required steam mass flow
- Annual fuel energy avoided by efficiency improvement
- Gauge to absolute pressure
- Latent heat at 212°F
- Steam heat transferred
- Water-heating load
- Steam required by a coil
- Steam volume from specific volume
- Flash-steam mass fraction
- Round-hole area for leak estimate
- Grashof steam-leak estimate
- Annual steam-leak cost
- Annual hot-water leak energy
- Condensate return pump head
- Saturated wet-steam quality
Industrial systems: air, pumps, fans, heat recovery 41
- Compressor annual energy and demand cost
- Dryer dew-point guideline
- Motor input from horsepower
- Filter pressure-drop savings estimate
- Pressure reduction energy rule
- Pressure-loss budget
- Engineered nozzle airflow rule
- Air mass flow
- Recovered annual kiln heat
- Fuel cost and displaced-fuel savings
- Installed project cost
- Annual compressor-air heat recovery
- Economizer electric-energy savings
- Electricity cost savings
- Area and spacing per fixture
- Spacing-to-mounting-height ratio (SHR)
- Annual demand-charge savings
- Annual lamp replacement cost
- Lighting cooling interaction
- Net annual retrofit savings
- Dust-control demand savings
- Dust-control electric savings
- Avoided exhaust heating cost
- Receiver transient support time
- Parallel-path supply pressure
- Product-air capacity with purge
- Pump electrical input
- System head requirement
- Quadratic curve operating flow
- Fan brake horsepower (BHP)
- Dynamic-system speed power
- No-production air leakage fraction
- Isothermal receiver free-air rate
- Compressed-air specific power (SP)
- Process refrigeration COP
- Steam turbine shaft power
- Sensible recovery effectiveness
- Net heat-recovery source benefit
- Speed under a fan power ceiling
- Load-unload leakage repair benefit
- Recovery and bypass mixing temperature
Renewables and on-site generation 36
- Heat rate and electricity-energy conversion (HR)
- Collector area at a stated irradiance
- Annual solar collection and value
- Solar capital and simple payback (SPP)
- Collector performance-curve variable
- Sensible thermal storage
- Gross solar-to-loss ratio
- Series-cell voltage
- Parallel-string current
- Wind-stream power in coherent SI units
- Imperial wind-power coefficient
- Screened usable wind power
- Wind-speed power ratio
- Water lost through leaked steam
- Cooling-tower evaporation rule
- Condenser-water temperature savings rule
- Solar gain over one selected period
- Seasonal heat loss from aggregate UA
- PV array power at a common operating point
- Hydropower from available net head
- Wet biomass useful-heat cost
- Wind energy from speed bins
- DC-to-AC useful power
- Annual electricity-energy savings
- Annual demand-charge savings
- Recovered-heat fuel-cost credit
- Existing-gas discount and total gas credit
- DG implementation cost
- Annual DG fuel cost
- Annual DG maintenance and materials
- DG net annual savings
- Annual worth comparison (AW)
- Capital-recovery factor (CRF)
- Electric efficiency on the same heat-rate basis
- On-site renewable annual benefit
- CHP primary-energy saving (PES)
Energy storage 27
- Required peak thermal storage
- Full-storage cooling capacity
- Partial-storage cooling requirement
- Water-tank sensible capacity
- Required chilled-water tank volume
- Required ice mass
- Hot-water sensible energy
- Storage round-trip efficiency (RTE)
- Battery nameplate capacity
- Battery support duration
- Battery ending state of charge
- Required charging energy
- Average charging power
- Capacity after degradation
- Annual storage demand savings
- Net cycle energy-price benefit
- Flywheel energy ratio
- Ideal load-leveling chiller size
- Available thermal charging output
- Required cooling discharge rate
- Cooling energy conversion
- AC energy above a reserve
- Electricity to charge ice storage
- Loss-adjusted charging price limit
- State after DC charge and discharge
- Two-period discharge requirement
- Minimum charging window
Controls and building automation 13
- Fan electricity cost savings
- Avoided exhaust-air heating cost
- Annual setback fuel-cost savings
- Measured chiller kW/ton
- Measured load reduction percentage
- Cooling output from a water-side meter
- Energy change with different operating schedules
- Limited outdoor-temperature reset
- Equal-load chiller staging crossover
- Linear analog scaling
- Unsaturated proportional output
- PI command after an integral update
- Differential pressure with separate zero corrections
Audits and field measurements 20
- Constant-temperature degree days (DD)
- Lighting inventory power
- Inventory operating energy
- Production-related energy index
- Daily heating degree days
- Daily cooling degree days
- Duration from degree days
- Single-phase measured real power
- Two-state logged energy
- Period load factor (LF)
- Electricity-only EUI
- Sensible heat from field airflow
- Water heat rate from field readings
- Duct airflow from velocity
- Equivalent full-load operating hours
- Combined electricity and gas energy
- Velocity for a target duct airflow
- Airflow inferred from a sensible heat rate
- Water heat integrated over two operating intervals
- Energy from a linear power ramp and plateau
Operations, maintenance and commissioning 11
- Three-phase voltage unbalance (VU)
- Electricity wasted by a measured excess load
- Failure and production-interruption cost
- Flow-normalized filter resistance
- Heat-transfer restoration ratio
- Serviced belt-drive speed
- Pump excess electrical input
- Area-based RCx cost estimate
- Bare ventilation equipment budget
- Schedule-correction energy reduction
- Behavioral plasticity percentage
Performance contracts and M&V 28
- Verification-budget screening guideline
- Adjusted energy savings
- Normalized model savings
- Level annual loan payment
- Period loan interest
- Principal repaid in a payment
- Annual bond coupon
- Present cost of lease payments (PV)
- Net annual on-bill benefit
- Shared-savings provider payment
- Savings guarantee shortfall
- Customer retained annual cash
- Option A power-and-hours savings
- Period-adjusted isolation savings
- Linear baseline prediction
- Added-load baseline adjustment
- Value of avoided energy
- Relative savings uncertainty
- M&V cost fraction
- Debt service coverage (DSCR)
- Principal allowed by coverage
- Independent combined standard error
- Interacting measure savings
- Maximum provider savings share
- Three-interval simulation RMSE
- Conservative savings claim bound
- Cash-neutral avoided energy price
- Break-even lease terminal charge
Benchmarking, budgets and carbon 30
- Energy utilization index (EUI)
- Energy cost index (ECI)
- Production energy intensity
- Weather energy intensity
- Floor area energy intensity
- Combined normalized intensity
- Sales energy intensity
- Energy cost share
- Labor or machine energy intensity
- Consumption cost variance
- Price cost variance
- Multiple-variable energy forecast
- Single-driver EPM
- Energy variance
- Cumulative variance
- Percent budget variance
- EPM parameter improvement
- Adjusted-baseline savings
- Energy cost per floor area
- Comparable cost reduction
- Floor-area energy cost index
- Weighted source-energy total
- Green product premium saving
- Activity-based emissions
- Refrigerant CO2-equivalent
- Relative emissions reduction
- Annual electric-energy balance
- Carbon-budget refrigerant handling limit
- Heat-pump carbon break-even grid factor
- Required lighting power reduction
Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.