EnerBusS instruments commercial and industrial refrigeration, chillers and heat pumps with ten field sensors, closes the energy balance over the compressor, and reports the true COP, capacity and System Efficiency Index of the plant as it runs — then turns the findings into verified kilowatt-hours.
Measured cycle on the log p–h plane. Two pressures, seven temperatures and one active-power reading fix points 1, 2 and 3; the refrigerant mass flow follows from the energy balance over the compressor, and every performance figure follows from that.
Refrigeration accounts for roughly 20 % of global electricity use and 50–60 % of the electricity of a typical supermarket. Yet a plant that holds its product temperature is universally judged "fine", and the only performance indicators most sites possess — a pressure gauge and a bill — cannot separate a good compressor from a worn one, or a floating-head setpoint from one left at factory default. Faults that cost 15–30 % of compressor energy are invisible to the cabinet thermostat and to the service technician's monthly visit.
Coefficient of performance moves 2–5 % for every kelvin of change in condensing or evaporating temperature. A COP quoted without its operating point is not a benchmark; the System Efficiency Index (SEI) is designed precisely to remove that dependence.
Fouling, oil logging, refrigerant loss, TXV hunting and control setpoints that "stuck" after a callout each shave efficiency slowly. Time-based maintenance checks pressures and temperatures, rarely efficiency — so the drift is only discovered at failure or never.
Energy-efficiency contracts, ESCO structures and green-financing covenants require an evidenced baseline and a post-optimisation measurement under equivalent ambient conditions. An energy-signature model of the plant (kWh/h versus ambient temperature) is the only defensible way to normalise the two.
Conventional field testing of a refrigeration plant needs a refrigerant or secondary-fluid flow measurement that is expensive, intrusive and rarely accurate. The internal method — first developed in Sweden in 1986, validated by the national testing institute (SP, today RISE) and since adopted by more than 50 manufacturers and 400 contractors in over 20 countries — instead uses the compressor itself as the flow meter, by closing the first-law energy balance across it.
Enthalpies are evaluated from the refrigerant equation of state at the measured states, including glide-correct handling of zeotropic blends (R404A, R407F, R448A/R449A, R134a, R290, R744 subcritical and transcritical). Because the method depends only on thermodynamic properties and the first law, results are independent of any manufacturer data and are reproducible on any vapour-compression plant.
The SEI is the measured COP divided by the Carnot COP between two agreed reference temperatures — the warm and cold media the plant actually serves, not its own refrigerant temperatures. Because the ideal cycle moves with the operating conditions, SEI is nearly independent of them, which makes plants on different sites, seasons and refrigerants comparable. The same measurement is then decomposed into four sub-efficiencies so that each loss mechanism is assigned to a component and a corrective action.
Indicative levels: state-of-the-art chillers with flooded evaporators reach SEI 45–55 % at full load; well-adjusted expansion-valve plants 40–50 %; a field-measured supermarket rack with fixed head pressure and hunting capacity control commonly sits at 30–40 %, and an air-cooled chiller left at factory fan-control defaults has been measured at 17 %. Sub-efficiency benchmarks then indicate whether the gap is a refrigerant-cycle loss (superheat, subcooling, pressure drop), a compressor loss (wear, part-load cycling, wrong staging), or a heat-exchanger loss (fouling, fan control, airflow).
EnerBusS is the exclusive partner in Greece for the analyser platform that implements the internal method, and delivers every service with the same instrumentation, the same thermodynamic engine and the same report structure — so a portfolio owner reads one language across every site.
A portable analyser is clamped to the plant in 20–30 minutes without stopping it. Within the same visit the engineer has COP, capacity, isentropic efficiency, SEI and sub-efficiencies, and can test setpoint changes live. Deliverable: a diagnostic report with prioritised corrective actions and their estimated annual impact.
A fixed analyser per rack, chiller or heat pump streams to the online platform: hourly energy signature versus ambient, daily performance profiles, compressor duty cycles and alarms on efficiency deviation rather than on temperature alone. Deliverable: monthly performance reports and a verified baseline for savings accounting.
Floating head pressure with a 5 K approach, minimum condensing limits by season, evaporating temperature and target superheat per rack, compressor staging and rotation, defrost scheduling and liquid-charge correction. Measures are implemented with the site's contractor and verified against the baseline signature.
Compressor isentropic efficiency, condenser approach and superheat stability are tracked as trends. A falling compressor efficiency, a rising approach or negative superheat is flagged weeks before it becomes a failure, a product loss or an emergency callout — converting maintenance from a cost centre into an asset-protection programme.
New racks, transcritical CO₂ plants, inverter retrofits, condenser replacements and heat-recovery installations are accepted against measured SEI and capacity, not against a nameplate. Retrofit business cases are settled with before/after measurement under normalised ambient conditions.
Results feed directly into building energy studies, ESCO contracts, ISO 50001 energy reviews, F-gas leak-rate evidence and EU-funded efficiency programmes. Delivered by chartered mechanical engineers with a track record in HVAC, hydronic and refrigeration design for public and private buildings.
The savings EnerBusS reports are not a vendor promise; they follow from well-established thermodynamic sensitivities and from decades of published field measurement. The table summarises the effects we exploit most often, with the sources listed at the foot of the page.
| Mechanism | Effect | Typical magnitude | How EnerBusS acts on it |
|---|---|---|---|
| Condensing temperature | Compressor energy per kelvin of condensing-temperature reduction | 2–4 % / K | Floating head pressure with 5 K condenser approach; seasonal minimum-condensing limits; fan-control defaults corrected. Monitored supermarket retrofits report 19–29 % annual compressor savings.Wheeler & Smith (ACEEE); Carbon Trust CTG046; Berglöf (IOR 2021) |
| Evaporating temperature | Compressor energy per kelvin of evaporating-temperature increase | 2–4 % / K | Raise evaporating setpoint to the highest value that still holds product temperature; correct excessive superheat that forces a lower evaporating pressure.Carbon Trust CTG046; IIR / Danfoss application guidance |
| Fan / control setpoints | Condensing temperature reduced by 10 K after correcting a fan-controller default | ≈ 30 % | Field case, measured by the analyser before and after; no hardware changed.Berglöf, IOR Annual Conference 2021 |
| Optimisation of existing plant | Range of measured savings from control correction, charge and superheat adjustment | 10–30 % | Standard programme outcome across supermarkets, industrial refrigeration, chillers and ice rinks; ROI typically under one year because most measures are settings, not equipment.Berglöf (IIR Prague 2011, IOR 2021); COOL-SAVE best-practice guide |
| Analytics-based commissioning | Median energy savings from fault-detection & diagnostics across a large building portfolio | 10 % | Same principle applied to refrigeration: continuous measurement, deviation alarms, corrective action, persistence tracking. Savings rose to 19 % by year four where the programme was sustained.Kramer et al., LBNL 2019 (5,200 buildings) |
| Refrigeration share of load | Share of a supermarket's electricity consumed by refrigeration | 50–60 % | Why refrigeration is the first place a retail portfolio should look: a 15 % refrigeration saving is a 7–9 % reduction in the store's entire bill.Maidment et al., IOR 2016; Thanasoulas & Molinari, Energy Reports 2025 |
| Global context | Share of worldwide electricity used by the refrigeration sector | ≈ 20 % | Refrigeration is the largest electricity end-use category in the cold chain; efficiency of existing plant is the cheapest abatement available.IIR Informatory Note 38, 2019 |
For an owner of supermarkets, cold stores, food-processing lines or a data-centre chiller plant, refrigeration is the single largest controllable operating cost and the single largest source of unplanned capital events. A performance-measurement programme converts both into managed, auditable quantities — with a cost structure that is small against the energy it governs.
The majority of the 10–30 % saving found in existing plant is realised by changing condensing and evaporating setpoints, superheat targets, staging logic and fan control. The instrumentation and engineering are the only investment; payback of the programme is typically within the first year at Greek commercial tariffs.
Compressor failure on a supermarket rack costs a replacement, an emergency callout and product loss. Trending isentropic efficiency, superheat stability and start frequency detects wear, liquid floodback and short-cycling weeks in advance; the same data ends the practice of running one inverter compressor continuously while fixed-speed units short-cycle.
Every site carries a measured baseline energy signature. Post-optimisation performance is compared at equal ambient temperature, giving verified kWh that satisfy ESCO shared-savings contracts, ISO 50001 reviews, green-loan KPIs and EU efficiency-fund reporting. Refrigerant leak evidence for F-gas compliance is a by-product of the same measurement.
Because SEI removes the dependence on operating conditions, an owner can rank fifty stores on one axis, allocate capital to the worst performers first, and hold contractors to a measured acceptance criterion at handover. Transcritical CO₂, HFC racks, glycol chillers and heat pumps are all assessed by the same engine.
Efficiency reduces Scope 2 emissions directly; continuous charge monitoring detects leaks early and cuts the Scope 1 refrigerant emissions that dominate the footprint of HFC plants. Both are reported from measured data rather than estimated factors.
EnerBusS pairs the measurement platform with chartered mechanical engineers experienced in HVAC, refrigeration and building energy studies, including EU co-funded public projects. Owners get one accountable party for diagnosis, specification, contractor supervision and verification.
Adjust the inputs to your portfolio. Defaults reflect a mid-size Greek supermarket: two racks, ~150 MWh/yr refrigeration electricity, a conservative 12 % saving.
Cumulative net cash flow, years 0–5, at constant tariff. CO₂ avoided is shown at 0.35 kg CO₂/kWh (approximate Greek grid factor). The model is illustrative: EnerBusS quantifies each site's saving from its own measured baseline before any figure enters a contract.
The method needs only that the plant compresses a refrigerant. It has been applied from a 3 kW display cabinet condensing unit to multi-megawatt ammonia and CO₂ industrial systems.
MT and LT racks, transcritical CO₂ boosters, condensing units, heat recovery to DHW and space heating.
Ammonia and HFC central plants, blast freezers, evaporative condensers, defrost and capacity-control strategy.
Process chillers, glycol loops, dairies, breweries, meat and poultry lines with product-specific kWh per tonne KPIs.
Hospitals, hotels, data centres, district and ground-source heat pumps — commissioning, SEI benchmarking and predictive maintenance.
Every report follows the same structure whether it covers one rack or a portfolio, so that findings are comparable between sites and between years. Each figure is generated from measured data on the online platform and every recommendation carries an estimated annual impact.
A first onsite assessment of one rack or chiller takes a single day, does not interrupt operation, and returns a diagnostic report with quantified recommendations. For portfolios, EnerBusS proposes a phased programme: pilot sites, verified savings, then roll-out of permanent monitoring.