CA CEG cheat sheet

Energy intensity = annual energy use / output (kBtu/ft², kWh/unit, or J per unit); normalize before comparing facilities.

Energy use index benchmarking compares a site to peers of the same function; adjust for weather, occupancy, and production hours.

Plan-do-check-act cycle: assess baseline, set goal, implement measures, verify savings, and re-baseline after major changes.

Prioritize measures by savings-to-investment ratio or simple payback; screen low-cost O&M measures before capital projects.

Energy policy must include scope, objectives, assigned responsibility, documented procedures, and management review.

Typical program sequence: commitment, baseline inventory, opportunity identification, prioritization, implementation, verification, reporting.

Utility bill analysis: separate energy (kWh, therms, MMBtu) from demand (kW) charges; demand charges often drive 30-50% of commercial bills.

Load factor = average load / peak load over a period; low load factor signals demand-charge reduction potential.

ASHRAE Level 1 = walk-through plus utility analysis; Level 2 = detailed survey with energy balance and cost estimates; Level 3 = investment-grade with detailed modeling.

Audit boundary and baseline year must be defined before data collection; state units, conversion factors, and data sources.

End-use breakdown methods: metered sub-loads, short-term logging, nameplate plus run-hour estimation, or calibrated simulation.

Degree-day method: annual energy ≈ UA × heating degree days × 24 / efficiency; use for envelope and boiler screening.

Instrumentation: power logger for load profiles, ultrasonic or clamp-on flow meter, infrared camera for envelope and electrical hot spots.

Report economics per measure: capital cost, annual savings, simple payback, and life-cycle cost or IRR where required.

Spot measurements must capture duty cycle; multiply instantaneous kW by measured run hours to estimate annual kWh.

Uncertainty in audit savings depends on data granularity; metered data beats nameplate assumptions.

IPMVP options: A = retrofit isolation with stipulated savings; B = retrofit isolation with measured savings; C = whole-facility metering; D = calibrated simulation.

Savings = baseline energy − reporting-period energy, with both adjusted to common conditions (weather, occupancy, production).

Baseline model options: constant, time-of-week, temperature-dependent (single or multi-variable regression), or simulation.

Regression quality checks: R², coefficient standard error, t-statistic, and residual plots; adjust models when operating conditions change.

Avoidance versus savings: savings are adjusted-baseline differences; unadjusted bill reductions ignore weather and activity changes.

M&V plan content: boundary, baseline period, measurement approach, adjustment method, verification period, and reporting frequency.

Routine adjustments reflect independent variables (weather, production); non-routine adjustments reflect physical changes to the system.

Measurement error compounds when subtracting two large numbers; prefer sub-metering when savings are a small fraction of total use.

Simple payback = initial cost / annual savings; ignores time value and savings after payback.

Life-cycle cost = present value of capital plus recurring costs minus residual value, discounted at the owner's rate.

NPV = Σ (net cash flow_t / (1+i)^t) − initial cost; accept projects with NPV > 0 at the hurdle rate.

IRR is the discount rate making NPV zero; compare to hurdle rate; IRR is unreliable when cash flows change sign more than once.

Savings-to-investment ratio = present value of savings / present value of investment; SIR > 1 is favorable.

Levelized cost of energy = total present-value cost / present-value energy produced; used to compare supply options.

Financing structures: capital budget, operating lease, capital lease, energy performance contract, on-bill repayment, and PPA.

Escalating energy prices raise savings value; test sensitivity of payback to energy price and capital cost assumptions.

Real power P (kW) = V × I × power factor (single-phase); three-phase P = √3 × V_LL × I × PF.

Power factor = kW / kVA; low PF increases line current, losses, and utility PF penalties; capacitors supply reactive power.

Total harmonic distortion: THD_V = √(Σ V_h²)/V_1 for h ≥ 2; IEEE 519 sets voltage and current distortion limits at the point of common coupling.

Harmonics from VFDs and rectifiers cause neutral overheating, transformer derating, and capacitor resonance; use K-rated or derated transformers.

Voltage unbalance = maximum deviation from average / average voltage; NEMA motors tolerate about 1% unbalance, which raises losses.

Demand ratchet: billed demand may be based on the highest peak over 11-12 months; one spike can set charges for a year.

Load factor = average kW / peak kW; improving it reduces demand charge per kWh.

Conductors and transformers follow I²R losses; loss reduction from power factor correction ≈ 1 − (PF_old/PF_new)².

Sensible heat equation: Q (Btu/h) = 1.08 × cfm × ΔT for air at standard conditions; latent Q ≈ 0.68 × cfm × Δgrains.

Water heating/cooling: Q (Btu/h) = 500 × gpm × ΔT (water).

Chiller efficiency: kW/ton = 12 / COP; COP = cooling output / electrical input in consistent units.

Air-side economizer uses outdoor air when its enthalpy or temperature is below return air; verify damper and sensor operation.

VAV systems reduce fan energy with variable speed; fan power follows the cube law: P₂/P₁ = (N₂/N₁)³.

Supply air temperature reset, static pressure reset, and demand-controlled ventilation are common low-cost control measures.

Refrigerant efficiency and charge affect capacity; superheat and subcooling verify charge and expansion valve operation.

Heat recovery from exhaust air (enthalpy wheel, runaround coil) reduces coil loads in high-ventilation buildings.

Boiler efficiency: combustion efficiency = 100% − stack losses; use stack temperature and O₂/CO₂ to set excess air.

Steam enthalpy: use saturated steam tables; latent heat is recovered only if condensate returns or steam is used for heating.

Steam trap failure: failed-open traps waste steam; failed-closed traps cause water hammer and poor heat transfer.

Flash steam forms when high-pressure condensate drops to lower pressure; recover it to a low-pressure header.

Blowdown controls TDS; excessive blowdown wastes energy; heat recovery from blowdown is a common measure.

Insulation reduces surface loss; bare hot surfaces above 120°F are candidates; use economic thickness analysis.

Steam leak of 1/8-inch orifice at 100 psig can waste substantial fuel annually; leak surveys are high-return O&M.

Boiler tune-up, O₂ trim, and stack economizers improve efficiency; condensing boilers require low return-water temperature.

U-factor is thermal transmittance (Btu/h·ft²·°F); R-value = 1/U; total assembly R sums component resistances including films.

Overall heat transfer coefficient UA = Σ (area × U) for each envelope element; used in degree-day calculations.

Thermal bridging through framing, shelf angles, and balconies reduces effective R-value; account for it in assembly U-factors.

Air leakage moves more heat than conduction in many buildings; blower-door testing quantifies infiltration (ACH50).

Window performance: U-factor, solar heat gain coefficient, and visible transmittance; low-e coatings reduce radiant transfer.

Infiltration estimate: Q ≈ 1.08 × cfm × ΔT; cfm from blower-door results scaled by natural-to-forced pressure ratio.

Cool roofs (high solar reflectance and emittance) cut cooling load; verify aged reflectance, not just initial values.

Vapor retarders belong on the warm side of insulation; misplaced barriers trap moisture and degrade insulation.

Luminous efficacy (lm/W) compares sources; LED systems typically 100-150 lm/W versus fluorescent near 80-100 lm/W.

Lighting power density = connected lighting watts / floor area (W/ft²); compare to code allowances by space type.

Lighting energy = watts × hours / 1000 = kWh; controls (occupancy, daylight, scheduling) cut hours, not just watts.

Motor efficiency: losses split among stator, rotor, core, stray, and friction/windage; premium-efficiency motors reduce all loss components.

Variable frequency drive affinity laws: flow ∝ speed, head ∝ speed², power ∝ speed³ for centrifugal loads.

Motor load estimation: input power from a power meter; avoid relying on nameplate current, which overstates load.

Oversized motors run at low load and poor power factor; right-sizing and VFDs are common measures.

Belt, coupling, and alignment losses are maintenance items; rewind versus replace decisions should compare efficiency.

CHP efficiency = (useful electric output + useful thermal output) / fuel input; typical total efficiencies reach 70-80%.

Power-to-heat ratio = electric output / useful thermal output; match to site thermal and electric loads.

Prime movers: reciprocating engines (fast start, low heat rate at small scale), gas turbines, microturbines, and steam turbines.

Heat rate (Btu/kWh) = fuel input / electric output; lower is better; 3,412 Btu/kWh is the theoretical minimum.

Waste heat recovery from furnaces, compressors, and process steam reduces purchased fuel; use pinch analysis to match sources and sinks.

Process heating efficiency improves with insulation, recuperators, regenerative burners, and oxygen trim.

Demand response and load shifting reduce peak charges; industrial loads with thermal storage are good candidates.

Steam and compressed-air systems are top industrial targets; compressed-air leaks and pressure setpoints are low-cost savings.

Solar PV energy = array capacity × capacity factor × 8,760 hours; capacity factor varies with location, tilt, and shading.

PV performance ratio = actual output / theoretical output at standard test conditions; captures soiling, temperature, and inverter losses.

Solar thermal: collector efficiency depends on inlet temperature and ambient; higher ΔT lowers efficiency.

Wind power in the rotor ∝ ½ ρ A v³; hub-height wind speed and shear profile drive siting.

Betz limit: maximum theoretical wind extraction is about 59% of kinetic energy in the stream tube.

Biomass and biogas energy depend on moisture content and heating value; dry basis versus as-fired basis changes results.

Renewable economics: levelized cost includes capital, O&M, and financing; incentives and net metering change cash flows.

Grid interconnection and net metering rules affect project value; verify capacity limits and export compensation.

Scope 1 = direct fuel combustion and process emissions; Scope 2 = purchased electricity/steam; Scope 3 = value-chain emissions.

CO₂ emissions = energy use × emission factor; use grid-average or location-based factors for electricity and document the source.

Market-based Scope 2 uses contractual instruments (RECs, PPAs); location-based uses grid average.

Carbon intensity = emissions / output (kg CO₂e per unit or per MWh); compare on the same boundary.

Greenhouse gas accounting uses global warming potentials; CO₂e = mass × GWP for each gas.

Energy savings translate to emissions reductions only through the marginal or average emission factor chosen; state the method.

Sustainability reporting frameworks require consistent boundaries and restatement when methods change.

Renewable energy credits and carbon offsets differ: RECs convey renewable attributes; offsets represent avoided or removed emissions.