In both business and home design, energy efficiency has become a factor. Green living is a multi-billion dollar industry that affects architecture, marketing, politics and culture — and like most cultural phenomena, it can be difficult to distinguish the facts from the hype. To truly live a green lifestyle, we need to know how energy efficient our appliances are. How ratings hold weight or if the scale is just a good sales strategy.
If you really want to understand the energy impact within your home, ask a scientist. After all, energy efficiency is a scientific term that was central to scientists like Newton and Faraday as well as inventors like Edison and Tesla. As Edison would have told you, heat energy and electrical energy are not the same, but they are related. This is why his earliest light bulbs did not work. The American Society for Testing and Materials uses either the Joule or BTU as its unit of heat measurement, while electrical work is measured in watts and a “kilowatt-hour” indicates the electrical energy consumption.
The EPA provides a basic formula for saving based on energy efficiency. The savings equal the baseline energy use minus the post-installation energy use. Take this number and add or subtract any adjustments. Thermal insulation is typically easy to calculate using this method. As an example, if you live in a New England state, replacing single-pane windows with ENERGY STAR-certified windows you’ll cut about 23.5 million BTUs from escaping your home. At $14.50 per million BTUs, you’ll save around $340 annually.
The same formula goes for appliances, but using the kilowatt-hour (kWh) usage. The kWh is defined as the power consumption of 1,000 watts for one hour; leaving a 1,000-watts bulb on for one hour is equal to one kWh. In California, one kWh costs a little more than 15 cents. Replacing a 60-watt bulb you only use one hour per week would save you around 39 cents per year. Changing ten bulbs that you use 10 hours per week would save around $40. Calculate your own savings here.
Thermal transfer and lighting have linear efficiency analyses, as you are still comparing BTUs to BTUs and kWh to kWh; you are measuring apples to apples, but refrigerators and air conditioning units require measuring apples to oranges. An A/C unit uses electrical energy to transfer heat out of a home, so we need to analyze the kWh compared to the BTU change. Because A/C units pump heat, the outdoor temperature becomes part of the calculation. In a place hot place like Arizona, an ENERGY STAR unit can move 36,000 BTU in one hour at a cost of 11 cents per kWh. After the cost of the new unit, upgrading to an energy efficient unit would save you around $1,200 per year.
The EPA’s savings formula includes an area for adjustments. Bonus: there are both state and federal tax and incentive programs that add to the savings. At the federal level, certain energy efficient upgrades can earn you up to 30 percent.
Make sure you are living green and your home is as energy efficient as possible. Make sure you are doing your part to ensure a healthy future for our children and the environment!