Compare two building energy management system quotes by whole-life cost, sustained and discounted payback, NPV, break-even savings rate, and scope-normalized cost.
The displayed values are fictional input examples, not market averages. Replace them with actual scope, bills, vendor evidence, and contract terms.
Higher study-period NPV
Quote A · On-premises
$41,925
Lower net initial investment
Quote B · Cloud
$82,000
Shorter discounted payback
Tie
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| Metric | Quote A · On-premises | Quote B · Cloud |
|---|---|---|
| Gross initial cost | $168,000 | $86,000 |
| Net initial investment | $168,000 | $86,000 |
| Year-one recurring cost | $17,500 | $29,000 |
| Base effective savings rate | 6.4% | 4.8% |
| Year-one net savings | -$6,748 | -$20,936 |
| Steady-year net savings | -$2,140 | -$17,480 |
| Simple payback | Not reached | Not reached |
| First payback crossing | Not reached | Not reached |
| Sustained payback | Not reached | Not reached |
| Discounted payback | Not reached | Not reached |
| 5-year NPV | -$183,526 | -$170,414 |
| 10-year NPV | -$212,201 | -$254,126 |
| Study-period NPV | -$212,201 | -$254,126 |
| Nominal cumulative ROI | -58% | -71.39% |
| NPV-zero proposed savings rate | 21.64% | 22.34% |
| Quote | Scenario | Proposed savings rate | Steady-year net savings | Study-period NPV | Discounted payback |
|---|---|---|---|---|---|
| Quote A · On-premises | Downside | 6.4% | -$5,212 | -$237,092 | Not reached |
| Quote A · On-premises | Base | 8% | -$2,140 | -$212,201 | Not reached |
| Quote A · On-premises | Upside | 9.6% | $932 | -$187,311 | Not reached |
| Quote B · Cloud | Downside | 4.8% | -$19,784 | -$272,794 | Not reached |
| Quote B · Cloud | Base | 6% | -$17,480 | -$254,126 | Not reached |
| Quote B · Cloud | Upside | 7.2% | -$15,176 | -$235,458 | Not reached |
| Metric | Quote A · On-premises | Quote B · Cloud |
|---|---|---|
| Net initial investment per m² | $17 | $9 |
| Net initial investment per point | $1,400 | $1,075 |
| Annual recurring cost per point | $146 | $363 |
| Gross initial cost per integration | $21,000 | $14,333 |
| Year | Baseline energy cost | Gross savings | Recurring cost | Replacement cost | Net cash flow | Cumulative cash flow | Discounted cumulative cash flow |
|---|---|---|---|---|---|---|---|
| 1 | $240,000 | $10,752 | $17,500 | $0 | -$6,748 | -$174,748 | -$174,427 |
| 2 | $244,800 | $15,667 | $18,025 | $0 | -$2,358 | -$177,106 | -$176,565 |
| 3 | $249,696 | $15,981 | $18,566 | $0 | -$2,585 | -$179,691 | -$178,798 |
| 4 | $254,690 | $16,300 | $19,123 | $0 | -$2,823 | -$182,514 | -$181,121 |
| 5 | $259,784 | $16,626 | $19,696 | $0 | -$3,070 | -$185,584 | -$183,526 |
| 6 | $264,979 | $16,959 | $20,287 | $20,867 | -$24,196 | -$209,779 | -$201,581 |
| 7 | $270,279 | $17,298 | $20,896 | $0 | -$3,598 | -$213,377 | -$204,138 |
| 8 | $275,685 | $17,644 | $21,523 | $0 | -$3,879 | -$217,256 | -$206,764 |
| 9 | $281,198 | $17,997 | $22,168 | $0 | -$4,172 | -$221,428 | -$209,453 |
| 10 | $286,822 | $18,357 | $22,834 | $0 | -$4,477 | -$225,905 | -$212,201 |
Official-source review date: 2026-08-16. This result does not determine a Korean public-institution BEMS obligation or exemption, design compliance, technical savings, grant award, tax or accounting treatment, or investment approval.
A building energy management system combines metering, data collection, analysis, controls, and operating workflows so a facility team can identify and correct waste.
Two offers carrying the same BEMS label can have very different commercial structures.
One may place servers and perpetual software on site, while another may lower the entry price and recover more cost through a cloud subscription.
Point counts, legacy-system interfaces, commissioning, training, calibration, data retention, and replacement responsibility can differ as well.
This calculator puts two quotes on one study period and discount-rate basis, then joins initial cost, recurring cost, planned replacement, and energy-cost savings into an annual cash-flow model.
Gross initial cost adds platform and hardware, meters and sensors, networks and installation, integration and commissioning, and training and internal effort.
Net initial investment subtracts only confirmed support attributable to the quote and is floored at zero.
The base effective rate equals the vendor-proposed savings rate multiplied by the savings-realization factor.
Year-one savings receive an additional ramp factor for data accumulation, control tuning, operator training, and incomplete first-year operation.
Annual net cash flow equals gross energy-cost savings minus recurring cost and any replacement scheduled in that year.
Baseline energy cost and recurring cost use separate annual change assumptions, so the model does not force benefits and costs to grow at one rate.
NPV treats net initial investment as a time-zero outflow and discounts each future net cash flow to present value.
Sustained payback is the interpolated crossing after the final negative cumulative balance, which prevents a replacement-year cash dip from being hidden by an earlier first crossing.
| Indicator | Meaning | Decision use |
|---|---|---|
| Simple payback | Net initial investment divided by steady-year net savings | Fast screening that omits discounting, escalation, and replacement timing |
| Sustained payback | Recovery after the last negative cumulative cash-flow point | Checks whether planned replacement reverses an earlier recovery |
| Study-period NPV | Present value of benefits less initial, recurring, and replacement cost | Compares alternatives using the same boundary, period, and discount rate |
| Break-even proposed rate | Proposed savings rate that makes study-period NPV equal zero | Minimum commercial performance line to compare with auditable vendor evidence |
| Boundary | Items to reconcile | Useful evidence |
|---|---|---|
| Metering | Electricity, gas, heat, temperature, humidity, flow, communications, and reused meters | Point list, single-line diagram, and site survey |
| Integration | BAS, facility systems, solar, storage, elevators, tariffs, read access, and control rights | Interface specification, protocol list, and responsibility matrix |
| Operation | Alarm tuning, analytics, reports, retention, backup, security patches, and user support | Service-level agreement, maintenance schedule, and data-return clause |
| Performance | Baseline adjustments, weather and occupancy, verification frequency, and underperformance action | Measurement plan, monthly source data, and performance terms |
| Replacement and exit | Server, gateway and sensor life, subscription exit, migration, and removal | Product life schedule, renewal quote, and transition plan |
The Korea Energy Agency describes BEMS as an integrated metering, control, management, and operating system that supports occupant comfort and efficient building-energy management.
Its public guidance covers sensor data for lighting, heating and cooling, gas, hot water, and renewable energy, together with collection, storage, inquiry, and performance analysis.
Review the current Korea Energy Agency BEMS guidance for the program and confirmation boundary.
A Korean public-institution energy-use rule effective April 30, 2026 includes BEMS construction, operation, installation confirmation, performance confirmation, and exclusions for certain covered public buildings.
A separate building energy-conservation design standard effective July 8, 2026 includes BEMS and remote electronic metering criteria.
Coverage depends on the institution, building, project, and approval facts, so verify current text through the Korean national law portal rather than treating a calculator result as a compliance decision.
The present-value model follows the general life-cycle-cost principle that alternatives need the same boundary, study period, service date, and discount basis, with initial, operating, maintenance, and replacement costs included where relevant.
NIST Handbook 135e2025 is a method reference only and does not supply BEMS prices, Korean discount rates, savings rates, or service lives.
Every market and project assumption therefore remains a user input.
An on-premises offer may require a larger server and license investment but a lower annual subscription, while a cloud offer can reverse that timing.
Compare five-year and ten-year NPV as well as sustained recovery after replacement instead of relying on the first invoice.
A lower quote with fewer points may be narrower rather than more efficient.
Compare cost per point and determine whether every added point supports an operating action, fault diagnosis, control, or savings verification need.
The break-even proposed rate is a useful starting point for a measurable commercial performance line.
If downside NPV is negative, consider a savings-verification plan, subscription cap, staged acceptance, and a corrective-action clause.
Facility teams often focus on scope, operations teams on recurring workload, finance teams on NPV, and executives on payback.
Producing all indicators from one cash-flow boundary reduces disputes caused by departments using different cost definitions.
Preserve it as the proposed rate, but do not automatically treat it as realized performance.
Set the realization factor after reviewing the baseline method, energy boundary, existing measures, weather and occupancy adjustments, and actual control authority.
Simple payback assumes one steady net-savings amount and ignores later replacement.
Actual cumulative cash flow can fall below zero again when a server, gateway, or meter replacement occurs, so the model also reports the crossing after the final negative balance.
The calculator does not embed a universal market rate.
Use contract-specific energy-price and budget forecasts, plus the discount rate used for investments with comparable risk, and apply the same assumptions to both quotes.
Keep the main decision case limited to support confirmed in writing.
Present a zero-support base case and a separate conditional case if approval is still pending, so the failure-to-award risk stays visible.
Use the fictional defaults only to learn the input structure, then collect normalized bills, the metering-point list, interface specification, service-level agreement, and planned replacement schedule.
Attach base and downside NPV, the break-even savings rate, and scope-normalized costs to vendor questions and the internal approval record so cost and performance responsibility remain explicit.