Many consumers who invest in solar photovoltaic systems make the mistake of not considering how energy efficient their home is to begin with. Energy efficiency is defined as delivering the same value with less energy input. In other words, an energy efficient home will enable someone to do the same things - heat and cool their home and power appliances in the same manner - but using less energy. Optimizing the energy performance of a building therefore makes sense before investing in a solar PV system, because a home will consume less energy and therefore require a smaller, less costly PV system. So where should one begin to make their home more energy efficient?
The first step is getting an energy audit. Energy audits are assessments of building's energy performance. For just a few hundred dollars, trained professionals will perform a series of diagnostics on a building to determine where energy loss is taking place or where opportunities exist to improve the energy performance of the home. At the end of an audit, the energy auditor will give a written report that outlines the most cost-effective ways to save energy. By some estimates, following through on energy audits, save the typical homeowner up to 30% on their energy bill.
One of the biggest inefficiencies in most buildings occurs due to air leaks in the building envelope that cause air to flow between outside and inside. Air flows from hot to cold locations so a building with a lot of air leakage will lose considerable amounts of treated air. In other words, hot and cold air is lost so a heating or air conditioning system has to work over time to maintain an optimal temperature. The result is that the building consumes more energy that it might need to should those leaks be sealed. One way to tell if a building is leaky is if temperatures are inconsistent in different rooms or areas. Adding insulation to a home's walls, attic and crawl spaces and sealing these air leaks is therefore one of the most cost-effective ways for someone to improve their home's energy performance. This minimizes heat transfer with the outdoors.
A lot of heat transfer also occurs through windows and doors, particularly in older homes with outdated windows and doors. As such, another way to improve the energy performance of a home's building shell is to make upgrades to its windows and doors. Newer models are designed to reduce convective and conductive heat transfer and for windows, block or trap radiant heat from the sunlight. Keep in mind that replacing energy inefficient windows and doors is typically a less cost-effective way to make energy improvements than sealing air leaks and adding insulation simply due to the higher price tag associated with windows and doors - insulating and air sealing products are very cheap and have higher returns on investment.
Lighting makes up approximately fifteen percent of most homes, electricity usage. Many homeowners use outdated bulbs, like incandescent bulbs, that consume large amount of energy. Switching to high efficiency light bulbs, like compact fluorescent light bulbs (CFLs), halogens, and light-emitting diodes (LEDs) is an easy way to reduce electric consumption. According to the United States Department of Energy, these high efficiency alternatives use 25-80% less energy than older bulbs and last 3-25 times longer. CFLs are commonly used in regular lamps. LEDs and halogens are best suited for recessed light fixtures or ballasts.
Most Americans have dozens upon dozens of electrical devices plugged into sockets throughout their home. From dishwashers and stoves to refrigerators and televisions, electrical devices are prevalent in most households and account for a considerable amount of energy usage. Fortunately, appliance manufacturers are constantly increasing the energy efficiency of the appliances that go to market. The United States Environmental Protection Agency (EPA) created a brand called ENERGY STAR that serves as a way to signify the most efficient products on the shelf. In other words, by looking for appliances with the ENERGY STAR label, homeowners can make upgrades to their electrical devices and save big on electricity. Visit ENERGY STAR's website for the full list of products.
Nearly half of all the energy a typical home uses goes towards heating and cooling expenses. As such, optimizing heating and cooling appliances is another major way to improve the energy performance of most homes. As a general rule of thumb, if a furnace, water heater or air conditioner is more than ten years old, it's probably pretty outdated and using way too much energy. Simply upgrading to an ENERGY STAR model can cut energy usage considerably.
In addition to upgrading heating and cooling appliances, it's also important to maintain your devices. Air filters should be changed every three months to make sure air intake and output are optimal. This also prevents dust and sediment from accumulating in the system, which can help extend the appliance's lifetime. Furnaces and air conditioning systems should also receive annual tune-ups from trained professionals - this ensures they're running optimally from an energy and comfort standpoint.
Finally, before investing in a solar PV system, homeowners should also attempt to naturally harness the sun through passive solar design. Passive solar design is essentially designing your home to optimize the sun's radiant heat naturally. This might mean maximizing radiant sunlight capture (in cooler climates or during winter) and/or minimizing radiant sunlight penetration (in warmer months or during summer). If done properly, passive solar design can reduce or even eliminate the need for heating and cooling systems.
Since North American homes receive sunlight mainly through the south side of buildings, most of the passive design takes place here. The type of design will depend on the building's climate.
During winter or in cooler climates that have high heating loads, a passive design will attempt to capture as much heat as possible from natural sunlight flowing into the south-facing windows and store it. This sunlight can also be used to provide adequate lighting to the home during the daylight thereby reducing the need for artificial lighting. Passive design systems here include a few basic elements. First, the windows must be properly oriented at approximately 30 degree of true south. Second, the windows should be unobstructed by objects like buildings or trees so they can maximize light capture during daylight hours. Third, thermal mass is a home's ability to store this captured heat. It's commonly stored by materials like concrete, brick, stone or tile on floors and/or walls. Finally, a distribution system should be installed to help transfer the heat to other parts of the home.
During summer months or in cooler climates, passive design works differently. Namely, homeowners will want to block out the sun light's penetration into the home to keep the home cool. Good passive design systems will have some type of control strategy that helps provide on demand shading over south facing windows. This can be done through sensing devices, like thermostats that signal some type of coverage - blinds, shades, awnings. Or it can even be using proper shrubs and trees that provide coverage via their foliage during the warmer months.