While the Home Energy Saver is the most comprehensive home energy model available on the web, there are inevitably specific systems or features that we have not yet explicitly incorporated. In some cases, there are reasonable work-arounds that the user can use to approximate the energy use of such features or systems. For example:
- Evaporative Cooling: HES does not model evaporative coolers. However, you can specify an appropriately high SEER (e.g. 22) in the air conditioning description to approximate the relatively low energy use of evaporative coolers. Note that this method will not yield any information about the water consumption by evaporative coolers, which also has a cost and other implications.
- Ground Coupled Heat Pumps: HES cannot currently model a GCHP ground loop. However, you can estimate the system performance using the ARI-330 ratings of the equipment. These can be obtained from the AHRI Directory of Certified Product Performance. For HSPF enter the COP at 32F * 3.2 and for SEER enter the EER at 77F. Note that this method will not account for the less extreme fluid temperatures provide by a ground loop.
- Extended Vacations: HES does not explicitly allow you to specify periods over which you may be away from your home, with consequent savings in energy use. One way to approximate this is to adjust the utilization factors (e.g. % of floor area heated or cooled, numbers of loads of clothes washed and dried, hours of appliance and lighting use, etc.) to reflect. For example, if you are away from your home 10% of the time, you could reduce the utilization factors by 10%. Keep in mind that some appliances will run irrespective of whether or not you are home (e.g. refrigerators). The time of year you are away will also have an effect on weather-sensitive energy uses.
- Line-drying clothes: You can account for this by adjusting the loads of clothes dried per week. For example, if you line dry half the time and wash 4 loads of clothes per week, you can specify 2 loads of week for clothes drying.
- Mixture of wall insulation levels on different stories: The site will let you create different wall construction types (and insulation levels), and they can be varied on each wall.. If different constructions are used on different stories of the house, we recommend inputting an insulation level that reflects the average of the two stories.
- Storm Windows: Many people have removable storm windows that slip into the existing window frame, providing an additional layer of glass and air space. We don't explicitly model this, but if the storm windows fit tightly and are used throughout the heating and/or cooling season, then specifying a window with one additional pane beyond the fixed number is a good approximation. If the fixed window is single-glazed, then specify dual-glazed; if the fixed window is dual glazed, then specify triple-glazed.
- Electric Cars: Do you have an electric car that's charged at your house? You can account for it under "Enter your own Electric Appliance" on the Small Appliances > other appliances input form. Find out the monthly electricity use by reading the charger's own meter (should be in kilowatt hours). Divide that number by 10, and we'll call that result "XX". Enter or select the following four options: "Used" XX "hours" per "month" and "drawing 10000 Watts." If, for example, your car charger was using 100 kilowatt hours per month then XX would be set at 10, and thus 10 hours x 10000 Watts = 100 kilowatt hours per month!
- Tankless Waterheaters: Although HES does not formally model tankless waterheaters, you can achieve a good approximation by using the detailed inputs and choosing an Energy Factor of 0.80 and a recovery efficiency of 1.00 for fuel heating or an Energy Factor of 1.00 and a recovery efficiency of 1.00 for electric heating. For all cases, set the Storage Tank volume to zero.