Annual Electricity Savings Research Articles

Unlocking energy and economic benefits of integrated green envelopes in office building retrofits

Green envelopes show significant potential in energy conservation and thermal comfort enhancement in office buildings. This study presents a comprehensive method integrating field tests, building energy simulations, and optimization in office buildings in Chongqing, China. A 20-year life-cycle cost analysis was conducted to evaluate the benefits of green roofs (using sedum lineare container-type planting modules) and green façades (featuring vertical kudzu greenery systems). The results indicate that green roofs could reduce peak temperatures by up to 34.3 °C, leading to daily energy savings of 12.5 % during summer. Green façades decreased the wall exterior surface temperatures by up to 3.4 °C and 5.1 °C on the test cold and hot days, respectively. The maximum annual building electricity savings per green-modified area was 22.8 kWh/m2 for the poorly-insulated building and 5.4 kWh/m2 for the well-insulated one. This study highlights the cost-effectiveness of green envelopes in improving building efficiency. The optimal retrofit measure for the poorly-insulated building was the combination of green roofs and daylighting dimming control systems, yielding a 20-year life-cycle net savings per floor area of 81.5 CNY/m2. For the well-insulated building, the daylighting dimming control system alone provided optimal net savings per floor area of 26.4 CNY/m2.

Innovative approaches for deep decarbonization of data centers and building space heating networks: Modeling and comparison of novel waste heat recovery systems for liquid cooling systems

The data usage surge drives greater data center demand, amplifying global CO2 emissions. Mitigating climate change necessitates reducing data center CO2 emissions. Reusing waste heat from data centers offers a potential energy efficiency boost and environmental impact reduction. This study utilizes liquid cooling technology to raise waste heat temperature for building space heating and introduces the concept of ‘data furnaces,’ where data centers directly supply waste heat to heat buildings on-site, reducing district heating consumption and lowering CO2 emissions. Efficiently designing a heat recovery heat exchanger system that accounts for both heat rejection and cooling sides of a liquid cooling system is crucial for achieving complete heat recovery without using heat pump, a commonly overlooked aspect in existing literature. To address this issue, we propose two heat exchanger schemes: connecting the building space heating network to the secondary side (Scheme 1) and the primary side (Scheme 2) of the cooling distribution unit. Implementing these innovations leads to the elimination of dependence on a heat pump, substantially cutting energy and CO2 emissions. Using TRNSYS software, we develop, model, and compare waste heat recovery schemes to curb district heating consumption and CO2 emissions. To demonstrate broad implications of the proposed approaches for energy efficiency and sustainability in the data centers and building space heating networks, a showcase study examines constant 25 kW waste heat from a direct-to-chip liquid-cooled rack in an office building with 285.7 MWh annual space heating demand. A novel waste heat recovery rate relationship graph is created to assist system design, uncovering an unexpected result in Scheme 2: waste heat recovery decreases as outdoor temperature falls. In contrast, Scheme 1 maintains a stable waste heat recovery rate around 25 kW, regardless of outdoor temperature fluctuations. As a result, Scheme 1 reuses 155.2 MWh of waste heat annually compared to 138 MWh for Scheme 2. Schemes 1 and 2 yield annual electricity savings of 2290.5 kWh and 905.2 kWh, respectively, for the cooling system. Both schemes achieve profitability within a year through a 25-year life cycle analysis (LCC) and substantially reduce CO2 emissions, with Scheme 1 saving 291,996 kgCO2 and Scheme 2 saving 258,192 kgCO2. The study addresses critical gaps in existing literature by emphasizes LCC. The proposed heat exchanger designs represent pioneering solutions for optimizing waste heat recovery, particularly in challenging climates. New findings offer substantial benefits to both liquid-cooled and air-cooled facilities, making significant contributions to achieve carbon neutrality in data center operations.

Techno-economic analysis on prospects and implementation of employing radiative cooling technology across broader atmospheric conditions

Achieving a transition to maximize the utilization of radiative cooling as a passive cooling strategy is challenging for several regions worldwide, mainly due to unawareness, lack of government support, and extreme seasonal climatic variations. Being characterized by a variety of atmospheric conditions from tropical coastline to arid regions along with humid highland areas to regions with continental atmospheric conditions, Pakistan faces significant seasonal and daily variations in atmospheric parameters, such as solar irradiance, temperature, precipitation patterns, humidity, etc., making it a steppe country with diverse atmospheric conditions and an energy-intensive economy dominated by fossil fuels. Therefore, following United Nation's Sustainable Development Goals, here we investigate the radiative cooling potential resource map across Pakistan, providing it as a sustainable alternative to lower the cooling demand by maximizing the emitted thermal radiation to the deep space and minimizing solar irradiance absorption by utilizing the materials' inherent properties of being highly reflective within solar spectrum range and extremely emissive within the atmospheric window. A comprehensive comparison between annual, seasonal, diurnal, and nocturnal radiative cooling capability is conducted and analyzed across all provinces of Pakistan based on the variation in regional climatic conditions. The yearly average radiative cooling capacity varies from 69.39 to 96.41 W/m2 due to swift variation from humid continental to arid climatic regions, with a 24.27 % discrepancy in daytime and nighttime radiative cooling potentials owing to the significant influence of solar irradiance. An office building model incorporating radiative cooling coating at the rooftop is further implemented to illustrate the real-case scenarios of using radiative cooling coatings as a cool roof. Compared to traditional roofs, applying radiative cooling coatings on the rooftop of a single-storey office building can reduce the annual cooling load by 76.01 to 112.77 kWh/(m2.year) for various cities under diverse climatic conditions. The annual electricity savings in several cities are estimated to be 30.40 to 45.11 kWh/(m2.year) based on the refrigerator COP of 2.5. The application of radiative cooling coatings on rooftops induces the incremental cost of 24 $/m2, with a simple payback period of 5.32 to 7.89 years in response to annual electricity savings across varying meteorological conditions. Besides, the maximum carbon emissions reduction is estimated to be up to 27.77 kg/(m2.year) based on a carbon emission factor of 0.606 kgCO2/kWh. In the end, valuable insights are discussed based on policy recommendations and limitations for developing strategies to adapt the radiative cooling technology on a broader scale based on innovative solutions, spreading public awareness, and offering financial incentives.

Research on Energy Savings of an Air-Source Heat Pump Hot Water System in a College Student’s Dormitory Building

Centralized hot water systems are commonly installed in college student dormitories, representing a typical application for such systems. To achieve sustainable and environmentally friendly heating solutions, air-source heat pump hot water systems have gained attention for their high efficiency and energy-saving characteristics. By implementing heat pump technology, China could make significant progress towards achieving its carbon neutrality goals by reducing energy consumption and associated emissions. In this study, the heating performance of an air-source heat pump hot water system was tested in the field over the course of a year at a university in Chongqing, China. A simulation model was constructed using TRNSYS software, and a time-sharing control strategy was proposed to analyze the system’s operating characteristics and energy-saving performance. Results showed a 6% increase in unit annual average Coefficient of Performance (COP) and annual electricity savings of 10,027 kW·h, with an energy-saving rate of 8.77% after time-sharing control. The study highlights the significant economic and environmental benefits of adopting sustainable energy solutions, particularly in the context of increasing global greenhouse gas emissions.

Quantification of the Impact of Solar Water Heating and Influence of Its Potential Utilization through Strategic Campaign: Case Study in Dimbaza, South Africa

This paper ascertained the performance of the evacuated tube solar water heater (SWH) coupled with an auxiliary electric heater with reference to the replaced electric water heater with the same storage tank capacity (200 L) in a building. It also examines the influence of the uptake of the SWHs in the community due to different campaign methods. The study evaluated the performance of a 4 kW electric water heater and a 2 kW input SWH with an auxiliary electric heater, and quantified the annual energy and cost savings. A survey using questionnaires was conducted among 150 residences in Dimbaza based on the house representative’s perceptions to replace their electric water heaters with solar water heaters (based on the monetary saving inscribed on the solar water heaters, the sensitization of the target population on the environmental benefits of the solar water heaters and both the monetary savings and environmental benefits). The findings revealed that by replacing the electric water heater with the solar water heater with an auxiliary electric heater, the annual electricity savings due to hot water heating was 4408.99 kWh and the net present value payback period was 4.32 years. The desire of the household representatives to replace their existing electric water heaters with solar water heaters due to the campaign strategies increased from 75 to 126. This study is capable of providing a mechanism to increase the penetration of solar water heaters and justifying the techno-economic viability of solar water heaters.

Performance evaluation and parametric analysis of an integrated diurnal and nocturnal cooling system driven by photovoltaic-thermal collectors with switchable film insulation

Cooling systems integrated with photovoltaic-thermal (PVT) collectors are promising for reducing building energy consumption because PVT collectors can provide photovoltaic power generation, solar thermal cooling, and nocturnal passive cooling. Glazed and unglazed PVT collectors have typically been used in previous studies, but they lead to conflicting goals for enhancing the all-day energy performance. Glazed collectors are favorable for solar thermal cooling but result in low nocturnal passive cooling capacity, while unglazed collectors exhibit the opposite behavior. In this study, PVT collectors with switchable film insulation (i.e., PVTfilm collectors) are introduced to drive an integrated diurnal and nocturnal cooling system. Such collectors can adapt to daytime and nighttime operating modes by inflating and deflating their air cushion. Annual (8760-hour) simulations were performed based on the case study of a tropical building. Three system layouts driven by different PVT collectors were compared. The effects of key optical parameters on energy performance were analyzed. The results show that the PVTfilm collectors combine satisfactory solar thermal cooling and nocturnal passive cooling performances, with an annual total energy yield that is 10% and 32% higher than those of glazed and unglazed PVT collectors, respectively. To improve the annual total electricity savings, it is advantageous to increase the film transmittance for solar radiation, decrease the film transmittance for long-wave thermal radiation and decrease the photovoltaic panel emissivity for long-wave thermal radiation. This work is relevant for PVT systems to improve the all-day energy performance and reduce building energy consumption.

As a case study, energy analysis application of a hotel business in private sector

In our study, a detailed energy study was carried out in a hotel business, which is a commercial building, energy saving potential was determined, measures that could be taken to increase energy efficiency and reduce energy consumption costs were determined and recommendations were presented. As a result of the measurements of the hot water installation line with the thermal camera, heat losses in the valves and flanges were observed and insulation was recommended. When the investment determined for insulation is made, it is calculated that there will be a decrease of approximately 17% in the annual energy consumption for the water installation. After heating, booster and fire pump motors with efficiency class EFF2 were replaced with IE4 efficiency motors, it is seen there is a 6.9% increase in motor efficiency. As a result of replacing the IE1 class engine used in the cooling system with an IE4 class engine, the engine efficiency is expected to increase by 6.2%. As a result of the replacement of halogen bulbs in the business with LED luminaires, the annual total electricity savings were calculated as approximately 19158.12 kW/year.

Economic, Exergy, and Environmental Analyses of the Energy Assessments for U.S. Industries

Abstract This paper highlights the expected versus actual outcomes of 152 energy assessments that were performed between 2011 and 2020. The 1317 energy-assessment recommendations (ARs) are grouped into eight categories. This study adopted four measures per each category of recommendations: annual electricity savings, annual gas savings, annual cost savings, and annual CO2 emission reduction. The first part of the analysis compares the expected to the actually implemented values of the measures applied to each recommendation’s category. It was found that the percentages of the actual to the expected electricity, gas, and cost savings are 26.6%, 11.4%, and 17.1%, respectively, while the percentage of the actual to the expected CO2 reduction is 22%. Moreover, the second part of the analysis presents each category's implementation rate and the reasons for rejecting the unimplemented ARs. Cash flow and expensive initial investment resulted in rejecting 25% of ARs. Furthermore, the study proposes techniques and strategies to increase ARs’ implementation rate and improve private energy services companies’ implementation rate. Finally, exergy analysis is added to show the improvement that energy assessment achieves regarding exergy and exergy efficiencies of different industrial applications.

Recovery of greywater thermal energy with a wire on a tube heat exchanger attached to a dishwasher.

Heat recovery and energy savings from the graywater of household appliances, such as dishwashers and washing machines, can encourage people to avoid the unhealthily long hours of hand dishwashing. In this experimental study, the size of energy saving that could be obtained from a domestic dishwasher with a wire on a tube heat exchanger attached was investigated. The study results validated that heat recovery from graywater is possible and equivalent to annual electricity savings of 53.48kWh. The efficiency of the dishwasher can be increased to approximately 16% by saving energy, and the economic value of efficiency increase can be $5.88 per year. With all fittings, pipes, and fixing equipment, the heat exchanger cost was also calculated to be $35 per machine, and the payback period is 5.94years per machine. The payback period can be shortened by achieving lower production costs with mass production. Furthermore, the possible reduction of CO2 emission by saving electrical energy was estimated to be 26.74kg. In Turkey, nearly 8 million units of dishwashers are in domestic use, the size of the annual energy saving can be 427.84GWh, and the economic value is $47.04M. By energy saving, approximately 213.92kt/year less CO2 released. PRACTITIONER POINTS: Graywater heat recovery with a wire on a tube heat exchanger was studied experimentally. The energy consumption and processing time of a household dishwasher is shortened by graywater heat recovery. With the decrease in energy consumption, a reduction was achieved in the CO2 emission released during the energy generation.

Dynamic Energy Modelling as an Alternative Approach for Reducing Performance Gaps in Retrofitted Schools in Denmark

When considering that over 80% of buildings in Denmark were built before the 1980′s, a holistic energy retrofitting of the existing building stock is a major milestone to attain the energy and environmental targets of the country. In this work, a case study of three public schools is considered for post-retrofit process evaluation. The three schools were heavily retrofitted by September 2018 with energy conservation and improvement measures that were implemented targeting both the building envelope and various energy systems. A technical evaluation of the energy retrofit process in the schools was carried out, when considering one year of operation after the completion of the retrofitting work. Actual data from the heating and electricity meters in the schools were collected and compared with the pre-retrofit design numbers which rely majorly on static tabulated numbers for savings evaluation. It was shown that the retrofit design numbers largely overestimate the attained savings, where the average performance gap between the expected and real numbers for the three schools is around 61% and 136% for annual heating and electricity savings, respectively. On the other hand, an alternative approach was proposed where calibrated dynamic energy performance models, which were developed for the three schools in EnergyPlus, were used to simulate the impact of implementing the retrofit measures. It was shown that implementing this approach could predict much better the impacts of the retrofit process with an average gap of around 17% for heating savings and 21% for electricity savings. Based on the post-retrofit process evaluation in the three schools, it was concluded that using dynamic model simulations has the potential of lowering the performance gap between the promised and real savings when compared to static tabulated approaches, although the savings are still generally over-estimated in both approaches.

Transitions towards energy-efficient appliances in urban households of Gujarat state, India

ABSTRACT Residential sector accounted for 24% of the total electricity consumption in India during 2009–10 and has almost remained around one-quarter over the last decade. A total of 163 same urban households were surveyed in 2018 to ascertain the change in penetration and use of energy-efficient (EE) appliances therein over 2010–18. There was a significant increase in their penetration across each enduse category with main changes being in air conditioners (ACs) (47%) and LED lights (over 38 times) over 2010–18. The weighted average relative electricity consumption decreased from 0.89 to 0.44 for ACs (1.5TR), 0.42 to 0.23 for lighting lamps, 0.95 to 0.54 for tubelights, 0.98 to 0.68 for refrigerators, and 0.94 to 0.69 for TVs, indicating the lowering of average energy consumption due to EE appliances. The annual electricity savings at household level were found statistically significant for transitions to EE ACs and ceiling fans.

Economic Analysis of Integrated Ground Source Heat Pumps on a Shared Ground Loop

An integrated geothermal system in which heat pumps for air conditioning and hot water both share the same ground loop was proposed in our previous study. Although this system produced electricity savings of 15% compared to a conventional system in which the two heat pumps operated on their own ground loop, practical requirements regarding further lowering the operation cost of the integrated geothermal system and the possibility of the energy savings being low during winter initiated further investigation into potential energy conservation measures at no initial cost increase, if possible. Outdoor reset control for hot water supply and sequential heat pump operation, both of which could be included at no extra cost, were subsequently targeted as potential measures for greater electricity savings and economic feasibility. When these measures were incorporated into the integrated geothermal system, electricity savings of approximately 25% during the heating season compared to the conventional system were predicted. Eventually it led to annual electricity savings of about 25% compared to the conventional system, which is up to 9.6 million South Korean won a year at today’s rates. Additionally, it reached the break-even point earlier than one year after installation.

A simulated case study of a library in Brazil to improve energy efficiency

The aim of this study is to quantify the energy savings of a library in the city of Foz do Iguaçu/Brazil, through simulations in EnergyPlus. Due to the great participation of air conditioning in the electric consumption of the building under study, the following proposals were studied: the exchange of the current split air conditioning units by a Variable Refrigerant Flow (VRF) system; the application of solar control films on the glasses; and both options together. The methodology followed these steps: firstly, it was simulated the current electricity consumption and the results were validated with real measures; secondly, the retrofitting measures were sized and implemented in the program and the energy savings were quantified; finally, an economic analysis was performed in order to determine the feasibility of the proposals. As a result, the VRF system showed an annual saving in air-conditioning of 42.08% related to the mini-split system. The annual electricity savings were 32.01, 2.14 and 32.80% for the VRF, solar control films, and both options together, respectively. The feasibility analysis of the VRF, considering financing and for a scenario consistent with the historical average growth of the electricity prices and inflation rate, showed that the use of a VRF instead of the splits units recovers the initial investment in 14 years. The application of solar control films proved to be economically unfeasible.

Quantifying potential savings from sustainable energy projects at a large public university: An energy efficiency assessment for texas state university

At Texas State University (TSU) in the United States, “sustainability” is pursued within the context of (1) a non-binding declaration in the University’s plan, and (2) a State legislative directive to reduce energy consumption. Grounded in these direct links between sustainability and energy use, this paper evaluates energy efficiency at TSU. The aim of the applied case study is to inventory current (business as usual) energy consumption levels at TSU, and to understand how those levels might change under a regime of more sustainable energy technology. The paper performs financial analysis to show that selected sustainable energy projects can not only reduce energy use at TSU, and thereby strengthen the University’s commitment to sustainability. Sustainable energy projects will also save the University money in the long run. The case study draws on a sample of the 13 on-campus buildings with the highest current levels of energy consumption. The approach of the paper is to determine the level of attractiveness of investing in new technology by calculating the Net Present Value (NPV) in terms of financial savings every year (simple payback) or a more extended period (cash flow model). The environmental impact is calculated in terms of CO2 emission based on Scope 2 methodology. We find that TSU could achieve annual electricity savings of 15,391,436 kWh (17% of its annual energy costs) from implementing selected projects and save more than $1,000,000 in annual costs. Overall, TSU could reduce CO2 emissions by 12,561.81 metric tons. The shortest payback period belongs to the pump replacement, and the most significant annual kWh saving is represented by the replacement of the lighting system. Solar panel installation has the highest upfront investment reaching more than $7 million, while its implementation will bring the highest environmental impact by avoiding 2926.81 metric tonnes of CO2 every year. However, the recommended minimum cost of energy at 14–16 (¢/kWh) for solar panel implementation cannot compete with the 8 cents per kWh paid for the electricity at San Marcos. The findings have immediate practical relevance for campus planning at TSU, and the methods are replicable and extendable for use by practitioners and researchers at other Universities or large institutions.

Energy efficiency and cost saving opportunities in public and commercial buildings in developing countries – The case of air-conditioners in Ghana

Available data and market surveys conducted in Ghana have shown that 60–80% of electricity consumed in offices of public and commercial buildings is used to run air-conditioners to provide indoor thermal comfort for productive office work. Electricity consumptions of these air-conditioners are relatively high and are in the range of 3000–5400 kWh/yr per air-conditioner depending on the brand and the cooling capacity. Low energy efficiency rating of the air-conditioners is a major contributing factor to their high electricity consumption.This present work has conducted studies on the energy efficiency of air-conditioners used in the offices of public and commercial buildings in Ghana. Technical data from a national survey conducted on air-conditioning equipment used in the country was used for this study. In addition, a power quality clamp meter was used to monitor the actual power consumptions of stratified samples of the conventional air-conditioners in the offices, as well as that of an inverter air-conditioner installed in an office.The results from this study show that over 85% of air-conditioners used in Ghana exist in the lowest energy efficiency ratio category (1-star) and the remaining percentages are in the next lower categories (2 and 3-stars). It has been determined that enforcing energy efficiency regulations to shift the air-conditioner market in Ghana into the higher energy efficiency ratio (EER) categories has huge benefits for the country. For instance, there are annual electricity savings potential of 260 GWh and 1770 GWh respectively for the year 2020 and 2030 using inverter air-conditioners which have higher energy efficiency rating (4-star equivalent) compared to the current lower EER air-conditioners in the country. It is also determined that if Ghana continues to follow business as usual with low EER air-conditioners, it will need to install electricity generation capacity of about 480 MW by 2030 to handle influx of low energy efficient air-conditioners alone.Financial analysis has also revealed that there is opportunity for electricity consumption cost savings of about US$ 1.96 billion from the year 2018–2030 with higher EER air-conditioners (4-star) being installed in the country compared to the current low EER air-conditioners.

COMPARISON ON ENERGY SAVING: GREEN ROOF AND GREEN WALL

Green building conveys undeniably numerous benefits to the environment, social and economic aspects. The most substantial benefit of green building is energy conservation. Green roofs and green walls are amongst the green components that are synonymous with green building. These green components are similar in nature as both are based on the concept of vegetation coverage on buildings. Vegetation is a well-known natural medium that performs the photosynthesis process where it releases molecular oxygen and removes carbon dioxide from the atmosphere. Many studies have proved that these two green components are efficient in reducing energy consumption of a building. Therefore, this study aims to examine and compare the annual energy savings conveyed by green roofs and green walls on residential buildings in Malaysia. The findings indicated that green walls provide greater annual energy savings than green roofs. The result shows that green walls are able to provide higher annual electricity savings for residential buildings at RM166 compared to green roofs, which provide savings of only RM139.

COMPARISON ON ENERGY SAVING: GREEN ROOF AND GREEN WALL

Green building conveys undeniably numerous benefits to the environment, social and economic aspects. The most substantial benefit of green building is energy conservation. Green roofs and green walls are amongst the green components that are synonymous with green building. These green components are similar in nature as both are based on the concept of vegetation coverage on buildings. Vegetation is a well-known natural medium that performs the photosynthesis process where it releases molecular oxygen and removes carbon dioxide from the atmosphere. Many studies have proved that these two green components are efficient in reducing energy consumption of a building. Therefore, this study aims to examine and compare the annual energy savings conveyed by green roofs and green walls on residential buildings in Malaysia. The findings indicated that green walls provide greater annual energy savings than green roofs. The result shows that green walls are able to provide higher annual electricity savings for residential buildings at RM166 compared to green roofs, which provide savings of only RM139.

Energy -Efficient Reconstruction of Public Lighting in Pravets Municipality from Bulgaria

Improving energy efficiency and reducing greenhouse gases is a central issue of the Europe 2020 strategy. Today enormous electric energy is consumed by the street lighting. Much of it could be saved through suitable energy-conservation measures (ECMs). The energy audit of the street lighting system in the Pravets municipality was carried out in compliance with the legislation in force in the EU and Bulgaria. Data about the present state of street lighting and electricity consumption for a period of 3 years were gathered and analysed. The baseline electricity consumption was defined. Classification of streets was done and the light class of the different categories streets was determined. The potential for energy savings was identified and a package of ECMs was developed. The annual electricity savings are 680 MWh (or 57,441 €/y) and the annual CO2 emissions savings are 557,640 t. The investment for implementation of the envisaged ECMs is 414,840 €. The expected electricity savings compared to the baseline are 75%.

Experimental research on a novel sun shading & solar energy collecting coupling device for inpatient building in hot summer and cold winter climate zone in China

According to characteristics of solar radiation in hot summer and cold winter climate zone in China, and hot water high demand and cooling load of air conditioning of the inpatient departments in summer, a novel equipment integrating shading and domestic water generation is proposed and analyzed by theoretical and experimental methods, which consists of four parts: Arc sun shading reflecting plates, vacuum heat collecting tubes, domestic water tank and cold water supply unit. An inpatient department located in Changsha city is selected as the experimental site. Three kinds of shading and collecting elements were tested by experiments, key design parameters, such as the cross section size of the shading reflector, the solar radiation intensity, the circulating water flow were evaluated. The results showed that: this novel equipment can absorb 2.5–2.8 times heat when compared with traditional vacuum tube solar collector; in the case study, 100% hot water demand of hospital can be met in summer, 31.7% in transitional seasons and 10.8% in winter; the annual air conditioning energy consumption can be reduced by about 2.7% and the annual electricity savings are estimated.

Effects of energy efficiency measures in district-heated buildings on energy supply

Abstract In this study we estimate the final and primary energy savings for different energy efficiency measures in a multi-apartment building when heated by small-, medium- or large-scale district-heat production systems (DHSs). The small-scale system is based on heat-only boilers, whereas the other two also include cogeneration of district heat and electricity. In the systems with cogeneration units, a change in building's heat demand may influence cogenerated electricity and hence the overall power system. For the building analyzed, the estimated annual total final heat and electricity savings were 136 (54%) and 30 MWh (52%), respectively, giving total annual primary energy savings of 177–289 MWh. This varies as the ratio of primary and final heat savings depends on the type of energy efficiency measure and the energy supply. For the same heat savings measure, a system with a heat-only boiler gave the highest primary energy savings, whereas a system based mostly on cogeneration of district heat and electricity in combination with averaged-efficiency standalone power plants gave the lowest primary energy savings. When the energy supply is based on energy-efficient renewable-based system, the differences in primary energy savings between large- and small-scale DHSs are minor for the same energy efficiency measure.