Good Case Study About Home Energy Audit And Critical Analysis
The use of electricity is indispensable in modern times. Almost all the gadgets used at home run on electricity. Due to the over usage of electric devices, the amount of electricity bill makes a hole in our pockets. Therefore, it is important to use electricity judiciously so that the exorbitant electricity bill can be done away with. This case study will make an assessment of a residential home energy, which is 1200 square feet of floor area, including two bedrooms, two bathrooms, and a big living area with an open kitchen inhabited by 3 people. The home energy audit tools need to be used for an effective management of energy efficiency of the house so that the factors influencing the electricity bill can be properly examined and a possible improvement can be made by reducing the energy input in the system without changing the output. If the use of energy can be optimized, it will make a positive impact on the consumer by saving on the energy bills and simultaneously ensuring that the electric appliances and equipments perform efficiently without causing damage to the environment.
1.1 Problem Statement
Increasing consumption of electricity mounts the electricity bill, burning a hole in the pockets of the consumers, who have least idea as to how to keep the usage of electricity under check. Besides, the age of the house and electronic devices used at home also contribute to the low energy efficiency.
This assignment purports to make an energy audit of a residence so that electricity can be used more efficiently, resulting in the reduction of electricity bill and future energy losses. This can be achieved by implementing a suitable solution of renewable energy system.
The objectives of the assignment are as follows:
Evaluating the home energy audit
Critically analyze the energy bill
Prepare Sankey diagrams
Investigate the renewable energy system for the house
Investigate the boiler, the central heating system, refrigerator, washing machine, and alternative sources of energy in more detail.
Cost evaluation for reducing the monthly cost on electricity bills in the long run.
2.0 Energy Audit
An energy audit of the house has been conducted. The findings are as below:
The total rated energy consumption of the house is found to be 1053.75 KWH. The consumption by type of appliance category is shown in the below pie charts:
Figure 1: Monthly Usage by Appliance Category (in KWH)
Figure 2: Monthly Usage percentage (%) by Appliance Category
It can be seen from the above pie chart that the central heater/air conditioner and water heater are the main contributors, accounting for 56% of the total electricity consumption. Kitchen appliances account for 24% of the total consumption.
Figure 3: Electricity Bill
As it is seen from the above home energy audit that there is a huge difference between energy for which the bill is being paid and actual effective energy being used. This is mainly due to the inefficiency of the appliances used at home and their ability to convert energy into effective modes for our usage. It is not possible to change all the appliances of the house or address all the issues related to all home appliances. It is important to take a look the appliances that consume maximum energy and try to address the issues related with them. To identify the major contributors to the electricity bill, a Pareto analysis was done and the results are as below:
Figure 4: Pareto Analysis
The water boiler consumes the maximum energy, accounting for 34.16% of the total energy consumption alone. The central heating/air conditioning system consumes approximately 21.35% of the total energy. Refrigerator, cooker and washing machines are the next three major contributors of energy. House lights consume almost the same amount of energy like washing machine and cooker. All other appliances put together only contribute to 4.94%. In this paper, the focus will be laid only on Water Boiler, Central Heating, Refrigerator, Cooker, Washing Machine and Lights for the analysis.
Currently, the home has an electric water boiler. However, gas water boilers are one of the more energy efficient as well as low cost options. As per research, gas boilers reduce the overall consumption of energy by almost 18-20% than an equivalent rated electric heater (Sauer and Schmeink, 2009). Although gas heaters may take more time to heat the water than electric heaters, but it is more energy efficient. The cost of a 50 gallon gas water heater is around £160 and its installation cost is approximately £300 (Sauer and Schmeink, 2009). There are other energy efficient gas heater options. A typical energy efficient gas run water heater costs £300-600 and the installation of the same may cost up to £300-500. Currently, the yearly electricity bill due to water heater comes close to £ 1,369.28. Therefore, replacing the electric heater with a gas water heater makes sense cost wise. The cost justification will be examined in section 5.
3.2 Central Heating
Central heating has many components that one can address. Firstly, one can invest in installing a more energy efficient heating system that is costlier to buy and install. Any normal heating system may cost up to £600-1000 and may incur almost the same amount for installation. It can give up to 10-15% improvement in energy consumption (Sauer and Schmeink, 2009).
However, many surveys conducted found that many homes, especially, the old ones were not designed in the most energy efficient way. Therefore, from those homes, a large percentage of energy (almost 50%) is lost and only a small percentage of the heat is used to keep the rooms warm. The below diagram illustrates the energy loss process:
Figure 5: Energy Loss (Kukral, 2010)
Putting proper glaze in the glasses of windows and roofs can reduce the heat loss substantially. The cost of glazing the house windows is as below:
The cost of putting an insulation coat on the roof and the walls is relatively cheaper and can be achieved with a onetime investment of £200. This is expected to improve the overall heating requirement by close to 20-25% (Sauer and Schmeink, 2009). However, it is not possible for a layman to understand whether the house is energy efficient or not. For that, a government agency can be called for inspection, and they can do the inspection and provide a report for £200.
Currently, there are two refrigerators in the house and those are the only appliances in the house running 24/7. Combined, they consume almost 14.35 % of the total energy bill. These refrigerators are old, and therefore, consume a lot of energy. Current, energy efficient fridges consumes much less energy. Refrigerators that are of the same rating as the one currently installed costs around £200 -£300, depending on the company and energy star ratings. The higher the energy star rating, the lower the energy consumption (Kukral, 2010). If one buys two 4-star rated refrigerators spending £500, he can expect to save around 25% of the electricity bill from refrigerators annually. The average life span of a refrigerator is 7 years.
Cookers and kitchen appliances consume close to 9% of the total energy. However, many a times, reducing the energy consumption for kitchen appliances is not possible. Energy efficient cooking devices are not available always, and even if they are available, they do not offer great savings. Therefore, for cooker, it is important that the usage is done properly. It is important to switch off the device when it is not in use. Cookers in standby mode consume energy because of inductive circuit within it. The best thing to do is to not only switch it off when not in use but to take out the plug from the switch board or use a smart surge protector that automatically cuts the circuit when the appliance is not in use (Kukral, 2010).
3.5 Washing Machine
The washer dryer unit alone consumes about 8.5% of the total energy consumed in the house. Washer dryer also comes with energy ratings. Just like refrigerators, it is important to buy highly energy efficient washer dryer. Buying an A+++ or A++ rated washer dryer can reduce energy consumption by almost 25% compared to the traditional old generation washing machines (Kukral, 2010). An energy efficient washing machine costs between £200 and £400.
Figure 6: Comparison of different types of lights (Horowitz, 2011)
Lights consume almost 8.2% of the energy. Lights are a well-researched area and many energy efficient options are available. Most of the lights installed currently are 50 watt incandescent lamps that are definitely not energy efficient than the ones available presently. Halogens are an option that can provide the same lumen (brightness) at almost 25% less energy ratings (Kukral, 2010). Halogens have slightly higher life than incandescent lights. CFL’s can give the same lumen at almost 75% less wattage. CFLs mostly have useful life of 6-10 years. LED lights also can provide similar brightness as incandescent lights at almost 75% less wattage. LEDs have a useful life of 15 to 25 years.
Figure 7: Sankey Diagram of Electrical Lamps (Horowitz, 2011)
The cost of incandescent lamps is £0.75 (approx.). A cost of one halogen lamp is close to £1.80. CFLs cost, on an average, £3.1 and LEDs cost £12.5 per bulb when purchased a bulk of 10 bulbs at a time (Horowitz, 2011).
4.0 Use of Renewable Sources of Energy
Figure 8: Solar Panel on the Roof (Boyle, 2012)
One other way, the energy bill can be reduced is the use of solar energy for boiling water. Due to inconsistent availability of solar energy, it cannot be used as the single source for heating water. However, it can be used in combination with gas or electricity to reduce the overall consumption. In many cases, it is found that solar and electric heater combination can reduce water heater energy consumption by almost 50% (Boyle, 2012). However, the main problem is the installation of the solar panel and the cost of installation. Assuming that the house has the required roof space to install solar panel (8 panel small Solar systems), the installation cost will be approximately £6,000-7,000 (Boyle, 2012). The life of the solar panels is expected to be 25 years. It involves a huge initial investment but installing a solar system not only will reduce energy bill, but will also reduce the central heating bill as it will also help reduce the heating requirement. Overall, it is estimated that it will reduce the heating requirement by 20% and water energy requirement by another 15%-20%.
5.0 Costing Justification
It can be seen from the above analysis that different energy efficient options are available for immediate or long term implementation for energy consumption reduction. All of those suggestions will definitely help reduce the energy cost and electricity bill. However, it is important to see if the investment to install the energy efficient appliances justifies the savings.
Let’s look at the input cost vs the cost savings in the below table:
Looking at the table, it can be seen that almost all of the energy saving options make sense in terms of return on investment. However, it is not possible to invest all of those immediately. Immediate investments should be made only those equipments that will give immediate energy reduction and financial benefit of the investment. The installation of a gas powered boiler (if options available), energy auditing the house, and then glazing the house, if required, should be done immediately. Among the light options, the payback period for CFL is lowest and the cost is also not as high as LED lamps. LED lamps are good for the long run but are costly options. Therefore, CFL seems to be the best option as of now.
Figure 9: Sankey Diagram of energy consumption currently.
Figure 10: Sankey Diagram at a future state (without solar power panels)
Most of the people have no idea as regards how much energy gets wasted every day in the homes. In fact, many will not believe that the lights used at home are less than 5% efficient and the rest 95% energy is wasted as heat. It is important for all of us to understand the energy bills and how we can optimize energy consumption given the budget constraint. It is important to understand the areas that have the potential to save energy. After doing energy audit at home, it was observed that water heater and central heater consume most of the energy, followed by refrigerator, washing machine and lights.
Water heater can be converted from electrical to gas powered unit and that will save energy as well as energy bill. Central heater energy consumption can be reduced by conducting an energy audit at home and then glazing the windows and insulating the roofs and walls. Light bills can be substantially reduced by using CFL or LED bulbs instead of incandescent or halogen bulbs.
Horowitz , N. 2011. New Energy-Saving Bulbs Are Coming -- Here's How You Find the Right Ones for Your Home. Natural Resources Defense Council. [Online] Available at <http://switchboard.nrdc.org/blogs/nhorowitz/new_energy-saving_bulbs_are_co.html> [Accessed 21 February 2015]
Boyle, Godfrey. 2012. Solar thermal energy. 3rd ed. London : Oxford. 34.
Bladh, M. (2010). Energy efficient lighting meets real home life. Energy Efficiency, 4(2), pp.235-245.
Sauer, J., Wastell, D. and Schmeink, C. 2009. Designing for the home: A comparative study of support aids for central heating systems. Applied Ergonomics, 40(2), pp.165-174.
Soundararajan, K., Ho, H. and Su, B. 2014. Sankey diagram framework for energy and exergy flows. Applied Energy, 136, pp.1035-1042.
Kukral, D. 2010. Keeping warm while staying green.. [Online] Available at <http://www.momgoesgreen.com/keeping-warm%E2%80%A6-while-staying-green/> [Accessed 21 February 2015]
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