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UV Coil Protection Savings Calculator

A transparent, budgetary screening estimate grounded in peer-reviewed findings — designed to earn trust, not force a conclusion.

Inputs
Defaults adjust schedules and typical HVAC intensity (editable in Methodology).
Enter blended rate.
References NOAA nearest major airport for CDD65
Primary sizing input. Used to estimate total HVAC tonnage using conservative industry averages.
Multiplies all results (screening only). Assumes similar sites.
Chilled water systems include additional chiller and pump savings per Rebecca et al. (2024) / ASHRAE RP-1738.
For chilled water recovery: Estimates reduced tower blowdown at 0.10 gal/ton-hr (~3% of evaporation). Typical municipal rate: $5-12.00/CCF.
Climate data reference (applied to calculations)
Climate: — CDD65: — Cooling weeks (est.): — Total tons (modeled): —
Financial Planning Inputs (Optional)
Used to estimate project cost, payback, and planning metrics. Does not affect calculated operating savings.
If left blank, screening cost will be estimated automatically based on total tonnage.
Optional annualized exposure based on replacement cost and risk %. Included in the waterfall total when enabled.
▾ O&M and optional budget exposure (editable assumptions)
Reported separately from energy for transparency.

Transparent UV ongoing costs (included)

▾ Advanced inputs (engineering controls)
Defaults are conservative and explainable. If you have measured schedules or BAS trends, adjust here.
Total tons = units × avg tons. Optional sqft override below.
Used only if sqft override is entered.
DX/packaged equipment efficiency. For chilled water systems, baseline kW/ton is derived from equipment age band (see Chiller kW/ton pill above) and is not controlled here.
Captures fan power across operating hours.
% of total cooling served by chilled water. Only applied when system type = Mixed. Default 60%.
Annual Net Operating Cost Reduction (Calculated)
$0
Utility (energy + water) + O&M − UV operating/lamps. Major repair risk reduction shown separately.
Energy savings: $0 O&M savings: $0 UV ongoing cost: $0
Incentives: $0
Cost of waiting
$0 / month
$0 / week (Calculated case)
Low / Calculated / High represent conservative, published, and fouled screening scenarios.
Value Composition (Calculated)
Shows how annual value is built. Incentives are one-time and shown if selected.
Financial Interpretation
Planning-level context based on calculated annual operating savings.
Return Profile
Simple Payback Energy + O&M savings, turn-key cost
—
Effective Payback Includes incentives, Sec. 179 & repair reduction
—
Simple Investment Ratio 10-year @ 4% discount rate
—
10-Year Outlook
Net Operating Value Before incentives & tax benefits
$0
All-In Planning Value Incentives, Sec. 179 & repair reduction included
$0
Estimated First Cost Planning estimate, before offsets
$0
Environmental Impact (Net Annual)
Net kWh savings and EPA greenhouse gas equivalencies based on screening-level results.
Net kWh Saved
0
Metric Tons of CO₂e
0
Tree Seedlings (10 yr)
0
EPA greenhouse gas equivalencies based on net kWh after UV energy.
Disclaimers
  • This is a preliminary screening estimate, not an audit. Actual results depend on coil condition, equipment type, controls, runtime, and tariff structure.
  • Energy savings are presented as a range (Low/Calculated/High). High values represent severe fouling scenarios and should be validated.
  • O&M and “Major repair risk reduction” are shown separately for transparency and to avoid double-counting.
  • No data is collected or sold by this static calculator. (Optional facility name is used only to label your printable report.)
Calculator v • Screening estimate
▾ Methodology & References (Screening-Level)
Energy savings mechanism (fan + cooling):
HVAC coil fouling impacts system performance in two distinct but related ways:
(1) Airside pressure drop (ΔP), which increases fan energy anytime the fan operates (cooling, heating, or circulation), and
(2) Heat-transfer degradation (ΔT), which increases compressor energy during active cooling operation.

This calculator models these effects separately and then combines them to estimate total energy recovery. Fan-related savings are applied across all modeled fan operating hours. Cooling-related savings are applied only during cooling hours. These effects are not double-counted; they represent different physical penalties caused by the same fouling condition.
This is a budgetary screening estimate intended to be explainable. It combines: (1) fan-related impacts (pressure drop/airflow) and (2) cooling impacts (coil heat-transfer degradation). Published field monitoring following UVGI coil irradiation has reported average improvements on the order of ~11% airside pressure drop and ~14.6% heat transfer coefficient in a hot-humid field case. This calculator uses conservative bands tied to HVAC age and cleaning frequency to produce Low/Calculated/High outcomes.
Climate
Cooling degree days (CDD65) are sourced from NOAA NCEI 1991–2020 climate normals at the nearest qualifying airport station. Cooling weeks are derived using CDD65 ÷ 70 (screening conversion).
Energy baseline
Cooling kWh ≈ tons × (kW/ton) × cooling hours × load factor. Fan kWh ≈ tons × (fan kW/ton) × annual fan hours.
Savings bands
Recovery percentages are determined by HVAC age band and coil cleaning frequency and are applied independently to fan energy (ΔP recovery) and cooling energy (ΔT recovery) before being combined into total savings. High values represent severe fouling and should be validated via inspection or pressure-drop evidence.
O&M lines
Coil cleaning and filter strategy are shown separately for transparency and to avoid double counting.
Major repair risk reduction
Optional: annualized budget exposure reduction = (replacement + major repair) / life × risk %. Not guaranteed savings.
Green metrics
Metric tons CO₂e = net kWh saved / 1412.1037. Tree seedlings grown for 10 years = net kWh saved / 85.336. (Net kWh accounts for UV energy.)
Chilled water systems (v2.6.0)
When system type is Chilled Water or Mixed, cooling recovery percentages use a parallel table (RECOVERY_TABLE_CW) anchored to a 15.62% UA improvement → ~16% integrated chiller+pump savings (Calculated mid-case), per Rebecca et al. (2024) and Firrantello & Bahnfleth (2018, ASHRAE RP-1738). Fan recovery is identical to DX — the airside ΔP mechanism is system-agnostic. Baseline chiller efficiency (kW/ton) is derived from equipment age band per ASHRAE 90.1 efficiency tiers (0.52 kW/ton for new equipment, 0.85 kW/ton for 20+ year equipment). Mixed systems blend DX and CW baselines and recovery percentages by the chilled water fraction (default 60%, editable in Advanced inputs). Centrifugal chiller efficiency peaks at 40–70% load (IPLV); UV restores fouled chillers toward their design operating point, so the linear screening assumption is considered conservative. IPLV-based analysis using BAS trend data is recommended for IGA-grade assessment.
Water savings (chilled water only)
Estimated at 0.10 gal/ton-hr of cooling operation — a conservative proxy for reduced tower blowdown frequency attributable to improved coil UA. This represents approximately 3% of total tower evaporation and is intentionally conservative for defensibility. Source: screening proxy informed by Rebecca et al. (2024) methodology.