How Does Your Home Measure Up?
For most of us, like death and taxes, purchasing electricity for the rest of our years is an inescapable consequence of powering our modern lives. But what if you could lock in your rate—and eventually produce your home’s energy for free? You also may be able to increase your home’s value, and take advantage of utility rebates, tax incentives, and the immeasurably good feeling of investing in clean, green energy for this and future generations.
Know Your Loads. The average American household uses about 900 kilowatt-hours (kWh) of electricity each month. But basing system costs solely on that number would most likely give you an inaccurate and unhelpful result. Your electrical use may vary wildly, depending on your habits, what kind of appliances you have, and the time of year.
So how can you gauge your electrical appetite? For a quick snapshot of your electrical usage, check out your monthly electricity bill. Most bills include kWh usage figures for the last twelve months; this will give you a good idea of how much electricity your home uses each year. This will give you a good idea of your total energy usage, but if you want to find out where your household energy hogs are, you’ll need to do a little more legwork.
A load analysis itemizes everything in your house that uses electricity (or energy), and then estimates how much each item uses in “watt-hours per day.” Point-of-use energy monitors allow you to determine which of your appliances are efficient, and which of them aren’t. For 120-volt electrical appliances, measuring energy use with a digital power meter, such as the Brand Electronics, Watts Up?, or Kill A Watt, will help you determine actual consumption and prioritize which appliances need to be replaced with more efficient units.
But watt-meters only give a small window into a home’s overall power use, since they are limited to measuring 120 VAC appliances—they can’t accommodate 240 VAC loads—and can only measure one appliance at a time instead of the whole household. (They can measure several appliances if used with a plug strip.) Several whole-house energy monitors are now available (like the TED5000) that even provide detailed graphs of your home’s energy use right on your computer.
Find—& Destroy—the Phantoms. A “phantom load” occurs when an appliance that appears to be off still consumes some electricity. Examples include appliances with clocks or indicator lights, remote controls, and plug-in power adapters. Although a few watts of standby energy use per appliance may sound like small potatoes, the combined energy use of these small loads adds up fast. Phantom loads in a typical American household use about 1.2 kilowatt-hours per day—the equivalent of some superefficient off-grid whole-house PV systems! Make efficiency easy to practice by using switched outlets or power strips to control these loads and make the switch on the strip easily accessible.
Whole-House Energy Audit. If you don’t have the tools (or the patience) to measure your own loads, consider hiring a home energy auditor. Home energy auditors gather information about the insulation, windows, water heater, and heating, ventilation, and air-conditioning (HVAC) efficiencies, dimensions, and all of the other data important to home energy use. Blower door and duct blaster tests, the second step, determine the air leakage of the whole house and of the heating/cooling duct system. Then they crunch the numbers from the first two steps, arriving at a home energy rating score (HERS) that comes from comparing the calculated energy consumption of the rated house to that of a reference house.
Home energy ratings can be a useful tool for any homeowner. So far, they’ve been used mainly to analyze and improve the performance of conventional, grid-powered homes, but the RE community should be taking advantage of them too. The HERS reports break down the heating and cooling consumption into the various components, such as above-grade walls, windows, infiltration, and ceilings. This allows you to put your money into those improvements that will save the most energy.
Getting to Zero Net-Energy Use—enabling your home meet all of its energy requirements from low-cost, locally available, nonpolluting, renewable sources is a worthy goal for many. There are a variety of ways that homeowners and builders alike can reach the goal of a ZEB, but typically they start with a grid-tied home. The grid can provide backup energy as needed and surplus energy, generated on-site, can be banked and accounted for in the home’s energy balance.
There are many ways to get to net zero-energy, but they all require accounting for all of your loads. Since different energy sources use different counting units, they need to be converted into a useful standard. It is most convenient to convert to kWh, because most net zero-energy homes use RE-made electricity to offset their total utility energy consumption.