Philippine consumer net metering experience

Philippine consumer net metering experience

This blog entry is about the QE (Qualified End-user) experience after installation of a Photovoltaic Generation system.

The installation is located south of Metro Manila Philippines. 

The installation is composed of 3 arrays:

2x 230 watts Canadian Solar PV module driven by micro inverter.
3x 235 watts Yingli PV module driven by micro inverter.
5x 250 watts Yingli PV module driven by a string inverter.

The total name plate capacity of the system  is 2,415 watts-peak.

History of the installation:

The installation started with 2x 230 watts array in early 2012.(http://www.eastgreenfields.com/solen-project)

The installation (lets now call it Project) was not expanded since Net Metering is not yet in place. Net Metering implementing rules and regulation (IRR) was only approved in late 2013.

The project was applied for net metering connection in 4th quarter of 2013, and was finally commissioned on July 2014.

When energized the total nameplate capacity was increased to 1,165 watts-peak. The Project capacity was further increased to 2,415 watts-peak as of mid-February 2015.

The electricity usage since the Project was approved for net metering increases, and the last 12 months average decreases. This means that the household now have extra electricity to power the appliances, while the import energy practically remains the same. Refer to graph below:

The last 12 months import average decreases while the actual load demand increases, this means more available energy for use generated from PV system. 

From July 2014 (when net metering starts) up to mid-February 2015 (before expansion to 2415 watts-peak capacity) the own use against exported energy is higher, but when the expansion system was put on-line the export energy is now higher than the own use energy.

Actual bill payment decrease as export credit increases.

Graph  shows the overview of the Project with the actual data from Meralco billing record.

Savings from actual load (usage of electricity without solar) ranges from 16% to 34% during the first 7 months of the Project with a capacity of 1165 watt-p system. The savings from actual load rises up to 63% when the system was expanded to 2415 watt-p capacity.

Following scan copy of the actual Meralco Bills...

Farm wastes as sources of renewable energy

By Rudy Romero
Manila Standard Today (online) 

Whenever they ponder alternative energy sources, most people usually think of energy derived from geothermal resources, the sun, wind and waves. They hardly ever think of a renewable energy source that, because of the abundance of its raw material, is one of the least expensive alternatives to oil. I am referring to methane gas derived from animal wastes.

Sometime in the 1980s, when I was doing investment-banking-type work, I was introduced to a German company that specialized in energy projects powered by methane gas generated from farm wastes. The company was looking for a Philippine partner for a methane gas project, with technology as their contribution thereto. Unfortunately, with Filipino alternative-energy mindsets oriented at that time towards geothermal and solar power, I was unable to package a project for the German company.

The technology for generating energy from farm wastes is relatively uncomplicated. Farm wastes – fecal matter from farm animals as well as residue from coconut and crop stalks – are collected, mixed and placed in containers so as to generate methane gas, which then goes into small turbines to produce electricity. The German executives said that with the methane gas generated by its animal and crop wastes, an average Philippine farm would be able to produce enough energy to light up the farmhouse and drive appliances and farm implements.

Given the promise that it offers, it is a great pity that renewable energy from farm wastes has not yet attracted many investors. As already pointed out, the needed raw materials are abundant in Philippine farms. This makes the production cost of farm-waste-generated methane gas probably the lowest among renewable energy sources.

A steady rise in the share of methane gas in total renewable-energy supply is not going to just happen. Much proselytizing will have to be undertaken by both the government and the private sector.

On the government side, the Department of Energy obviously will be the lead agency. More specifically, it is the Energy Development Corporation that will have to be in the forefront of development of a farm-waste-based methane gas industry. Because farm wastes are involved, the Department of Agriculture and the Department of Agrarian Reform also will have to play major roles in the effort. The Department of Science and Technology also will be a key player.

On the private-sector side, it is the agricultural-industry organizations that will have to be depended upon to spread the message about the attractiveness of farm wastes as a source of energy. Particularly important will be the farmers’ and farm workers’ organizations in the coconut, sugar, rice and corn industries. These industries account for most of the farm wastes in this country. For the sugar and coconut industries the farmers’ organizations concerned are the National Federation of Sugarcane Planters and the Philippine Coconut Federation, respectively.

Just how abundant and powerful methane gas can be as a source of renewable energy can be seen from the gas fumes emanating from city and municipal garbage dumps. Before it was redeveloped, Smokey Mountain used to emit a lot of methane gas from all the recyclable and non-recyclable wastes dumped there by the local authorities. Indeed, small flames would erupt when mistakes were thrown at the dumps.

A vibrant methane gas industry based on farm wastes: that is something to be fervently wished for. It can happen. For the more stable development of the Philippine countryside and the rapid progress of the Filipino farmer, it should happen.

http://manilastandardtoday.com/2015/03/17/farm-wastes-as-sources-of-renewable-energy/

Solar Power 101: Getting Started with Solar Electricity

Getting Started with Solar Electricity

Part 4 of 4 Series

From HP online magazine

With grid-tied PV systems becoming more and more popular, it is important for RE professionals and system owners alike to have realistic expectations of their systems’ performance. Solar-electric power production can be affected by several factors. Orientation, array tilt, seasonal adjustments, and array siting can all affect the bottom line. Proper planning and smart design will help you get the most out of your PV system and improve your rate of return. Installing modules in a sunny, shade-free spot and pointing them toward the sun could be considered common sense to many, but properly orienting and tilting your array for optimal performance is not as intuitive. A PV array’s output is proportional to the direct sunlight it receives. Even though PV modules produce some energy in a shady location or without ideal orientation, system costs are high enough that most will want to maximize energy yield. Regardless of how well a system is designed, improper installation can result in poor performance. PV systems should operate for decades, and the materials and methods to install them should be selected accordingly.

Should you install your system or hire a licensed professional to do the work? What skills and tools do you need to tackle a home-scale PV project? How much will you save if you install the system yourself? We frequently get questions like these from Home Power readers. Rather than defaulting to the obvious answer, “it depends,” we explore a long list of variables you should thoughtfully consider before tackling the design and installation of your PV system. Owner installation is definitely not for everyone. Like any home improvement project, it’s important to realistically assess your skills, and weigh the benefits and potential pitfalls. Installing a PV system certainly isn’t rocket science, but doing it well and safely requires experience working with electrical systems, some serious research, and plenty of sound advice. The installation of most residential PV systems is usually better left to the pros, but if you have the right set of skills and expectations, installing your own system can be a realistic goal.

Solar Power 101: How to Implement Solar Electricity

How to Implement Solar Electricity

Part 3 of 4 Series

From HP Online Magazine

As discussed in Step 1, there are several different applications for PV systems. Which system is right for you depends on your particular situation and RE goals. Due to available incentive programs and the simplistic nature of batteryless grid-tied PV systems, they are the most common type of system installed in the United States today. Here is a checklist to see if this type of system might work for you:

Interested in clean power? Check.
Already on the grid? Check.
Infrequent utility outages? Check.
Have a sunny location to mount PV modules? Check.
If this describes your situation, then a batteryless grid-tied PV system could be the perfect fit. Compared to their off-grid counterparts, batteryless grid- tied systems are simple to understand and design, with only two primary components: PV modules and an inverter that feeds AC electricity back into the electrical system to offset some or all of the electricity otherwise purchased from the utility. These systems are cheaper, easier to install and maintain, and operate more efficiently than battery-based systems of comparable size. Their main drawback is that when the grid goes down, they cannot provide any energy for you to use. If the grid in your area is mostly reliable and outages are infrequent, these systems can offer the best payback for the least price.

The primary goal of a grid-tied PV system is to offset all or some of your electricity usage. Yet the first step in going solar is not sizing the PV system, but reducing electricity usage through conservation and efficiency measures. Once energy-efficiency and conservation measures have been implemented, you’re ready to size a PV system to offset the remaining energy usage. Annual energy use figures can be requested from your utility, and these values can be used to determine the PV array size. However, there are a few other considerations that will impact PV system size. In residential areas especially, a primary constraint to PV array sizing can be the size of the available shade-free mounting area. PV modules can be mounted on a roof, the ground, or a pole (which includes trackers). Regardless of which mounting method is used, the shade-free area, minus clearance needed for maintenance or roof setbacks required by local fire department guidelines, will limit how large the array can be. In the case of roof-mounted systems, typically 50% to 80% of a roof plane will be available for mounting PV modules. Often the most confining consideration is budget. Currently (early 2012), the cost per installed watt of residential PV systems ranges from $5 to $8, which includes everything—modules, inverter, disconnects, racking, wire, and conduit to taxes, shipping, installation labor, and permitting. Reducing the cost is the uncapped 30% federal tax credit. Additionally, many individual states, municipalities, and utilities offer rebates that can further offset a PV system’s cost. The Database of State Incentives for Renewables & Efficiency (DSIRE; www.dsireusa.org) organizes incentive programs by state and program type, making incentives easy to research.

Off-Grid Systems: Living off the grid is a romantic ambition for some; a practical necessity for others. But whatever your motivation for off-grid living, cutting the electrical umbilical cord from the utility shouldn’t be taken lightly. Before you pull out the calculator, size up the realities and challenges of living off the grid. Designing a stand-alone PV system differs substantially from designing a batteryless grid-direct system. Instead of meeting the home’s annual demand, a stand-alone system must be able to meet energy requirements every day of the year. Determining the home’s daily and seasonal energy usage, along with considering the daily and seasonal availability of the sun, allows designers to estimate the PV array and battery bank size, and charge controller and inverter specifications. 

Solar Power 101: Why Use Solar Electricity?

Why Use Solar Electricity?

Part 2 of 4 Series

From HP Online Magazine

When we consider the true cost of energy, we need to look at the big picture, not just the rate on the utility bill. Conventional fuels have real social, environmental, and economic impacts. There are annual and cumulative costs that stem from all of the pollutants (airborne, solid, and liquid) emitted from mining, processing, and transporting fossil fuels that impact our public health and the environment. Electricity derived from coal and natural gas will never be able to outweigh the energy and continual resources required to produce it. Unlike conventional energy sources, PV systems produce clean electricity for decades after achieving their energy payback in three or fewer years—this is truly the magic of PV technology.

Grid electricity is paid for as you use it, with payments stretching out forever. In contrast, the majority of PV system expenses are paid for at the time the system is installed. After that, the energy is essentially free. In strictly economic terms, the rate of return for your PV system depends on three things—solar resource; electricity prices; and state policies or incentives. While many utilities sell electricity at affordable rates, inflation as well as energy price history and forecasts indicate price increases in our future, which will make RE systems’ payback even quicker. Historical data reported by the Edison Electric Institute shows that from 1929 to 2005, the average annual price increase for electricity has been 2.94% per year. And according to the Energy Information Administration’s June 2008 Short Term Energy Outlook, utility rates are projected to increase by an average of 3.7% in 2008 and by another 3.6% in 2009. Federal tax credits for renewable energy systems are available, reducing a RE system’s cost, and many states, regions, and utilities also offer substantial rebates, performance-based incentives, tax credits, tax exemptions, loans, and other economic incentives for solar-electric systems.

Independence is chief among the reasons for wanting an off-grid PV system where the grid is available. Off-grid systems are not subject to the terms or policies of the local utility, nor are system owners subjected to rate increases, blackouts, or brownouts. If you’re shopping for rural property, you’ll probably find that off-grid parcels are less expensive. Being off-grid can also be cheaper than getting a utility line extended to a property.

When weighing the energy options (between the grid and solar, wind or water sources) it becomes apparent that solar energy is a very democratic form of energy. Because the sun shines everywhere, the potential to utilize solar energy is available to everyone. Additionally, as compared to generators (gas, or even wind- or hydro-powered ones), because PV systems have no moving parts, they are extremely reliable and require very little maintenance.

Solar Power 101: Basics

Solar Electricity Basics
Part 1 of 4 Series

From Home Power (HP Online Magazine)

What is Solar Electricity?

Photovoltaic (PV) modules make electricity from sunlight, and are marvelously simple, effective, and durable. They sit in the sun and, with no moving parts, can run your appliances, charge your batteries, or make energy for the utility grid.

A PV array is the energy collector—the solar “generator” and does so via the photovoltaic effect. Discovered in 1839 by French physicist Alexandre-Edmund Becquerel, the photovoltaic effect describes the way in which PV cells create electricity from the energy residing in photons of sunlight. When sunlight hits a PV cell, the cell absorbs some of the photons and the photons’ energy is transferred to an electron in the semiconductor material. With the energy from the photon, the electron can escape its usual position in the semiconductor atom to become part of the current in an electrical circuit.

Most PV cells fall into one of two basic categories: crystalline silicon or thin-film. Crystalline silicon modules can be fashioned from either monocrystalline, multicrystalline, or ribbon silicon. Thin-film is a term encompassing a range of different technologies, including amorphous silicon, and a host of variations using other semiconductors like cadmium telluride or CIGS (copper indium gallium diselenide). Thin-film technology generates a lot of the current R&D chatter, but crystalline modules currently capture more than 80% of the marketplace.

To use the energy from the array, you may also need other components, such as inverters, charge controllers and batteries, which make up a solar-electric system. The components required are dependent on the system type designed. System types include:

PV-DIRECT SYSTEMS: These are the simplest of solar-electric systems, with the fewest components (basically the PV array and the load). Because they don’t have batteries and are not hooked up to the utility, they only power the loads when the sun is shining. This means that they are only appropriate for a few select applications, notably water pumping and ventilation—when the sun shines, the fan or pump runs.

OFF-GRID SYSTEMS: Although they are most common in remote locations without utility service, off-grid solar-electric systems can work anywhere. These systems operate independently from the grid to provide all of a household’s electricity. These systems require a battery bank to store the solar electricity for use during nighttime or cloudy weather, a charge controller to protect the battery bank from overcharge, an inverter to convert the DC PV array power to AC for use with AC household appliances, and all the required disconnects, monitoring, and associated electrical safety gear.

GRID-TIED SYSTEMS WITH BATTERY BACKUP: This type is very similar to an off-grid system in design and components, but adds the utility grid, which reduces the need for the system to provide all the energy all the time.

BATTERYLESS GRID-TIED SYSTEMS: These most common PV systems are also known as on-grid, grid-tied, utility-interactive, grid-intertied, or grid-direct. They generate solar electricity and route it to the loads and to the electric utility grid, offsetting a home’s or business’s electricity usage. System components are simply comprised of the PV array, inverter(s), and required electrical safety gear (i.e., fuses/breakers/disconnects/monitoring). Living with a grid-connected solar-electric system is no different than living with utility electricity, except that some or all of the electricity you use comes from the sun. (The drawback of these batteryless systems is that they provide no outage protection—when the utility grid fails, these systems cannot operate.)

Efficient Home Lighting Choices

By: Chris Calwell
HP Online

Instead of trying to put a CFL in every socket, savvy homeowners interested in energy efficiency are increasingly pursuing a more nuanced strategy: Choose the right technology for each application to deliver optimal performance and cost-effective energy savings.

Understanding Lighting Terminology

The most familiar (but perhaps the least useful) way of comparing lightbulbs to each other is wattage, which tells you how much power is consumed but tells you nothing about how much light the bulbs will provide—or whether you will like their light quality. Other key terms include:

Wattage Equivalent. Most energy-saving lightbulbs claim wattage equivalent, often in bold, colorful text at the top of the package. Ignore this! The federal government declined to regulate how manufacturers calculate and report wattage equivalency, so the claims products make are all over the map and often deceptive. It’s smarter to shop on the basis of measured light output instead (see the “Lumens Equivalent” table for comparative information).

Lumens are the measure of the absolute amount of light a bulb provides. An integrating sphere is one measuring tool that’s used. It first captures the bulb’s total light output in all directions across all the different wavelengths of light. Then it weights the resulting values to reflect the human eye’s sensitivity to each wavelength, summing up all the weighted values to give an overall measure of “useful” light output. Dim bulbs may only deliver 200 lumens or so, while really bright ones can deliver 2,500 lumens or more.

Efficiency. If one lighting technology can deliver more lumens of light per watt of power consumed, it is said to be more energy efficient. Lumens per watt is the figure of merit for efficiency, but that almost never appears on product labeling or packaging, so you have to calculate it from the values that are provided separately. For example, say a standard 60 W incandescent is rated at 750 lumens—that’s 12.5 lumens per watt. Compare this to a 14 W compact fluorescent rated at 900 lumens—that’s 64.3 lumens per watt. Efficiencies can range from as little as 5 to more than 100 lumens per watt, depending on the technology you choose and the amount of light you need.

Lifetime is now reported in years on product labels and assumes three hours of operation per day (a little higher than typical usage according to utility studies). Also, remember that the difference between a projected lifetime of 20 years and 25 years on two products is probably not meaningful, given the uncertainties in the accelerated lifetime testing process and the degree to which new lighting products will continue to improve between now and then. From a practical standpoint, the warranty a manufacturer offers is more useful; the highest-quality products usually offer a 10-year warranty.

Color rendering index (CRI) tells you how accurately a bulb renders a particular subset of colors (primarily pastels). A CRI of 80 or greater is usually recommended by lighting experts, but there is debate in the lighting community about the merits of paying extra money for products with a CRI greater than 90—most users can’t tell the difference under typical household lighting conditions.

Correlated color temperature (CCT; reported in Kelvin, K) tells you how “warm” or “cool” the light from a bulb appears.  Residential users typically favor warm (approximately 2,700 K) CCTs similar to incandescent bulbs, or 3,000 K (similar to halogen bulbs). In the 4,000 K to 6,000 K range, the resulting light can appear bluish. It is common for people who live in very sunny and tropical locations to favor bulbs with higher CCTs, given their greater similarity to daylight or midday sunshine.

The Energy Star label appears on energy-efficient products that deliver good performance in most of the attributes listed above. But thousands of models now qualify for it, so you need to be more selective to find the best performers. Also, be aware that many new energy-saving lighting products are introduced to market a few months before they have completed enough accelerated lifetime testing to earn the Energy Star label. The manufacturer will later change the packaging to reflect receipt of that certification, but the product inside the package can often be the same as the one selling a few months earlier without the logo.  This means that the most recently introduced models without an Energy Star logo can occasionally be more efficient and affordable than older models that are labeled.

More specialized information can often be found on product packages or manufacturer websites, including beam angle and center-beam candlepower for reflector lamps, compatibility with common dimmers, etc. If you are buying a large number of efficient bulbs, check online reviews to find products that have been consistently popular with other users, or buy from a retailer that will allow you to return the products for a refund if you are unhappy with their performance.

Lighting Technologies

Incandescent bulbs employ a thin tungsten filament that conducts enough electricity to glow white hot. Although this technology is more than 100 years old now, it has received only a few upgrades since Thomas Edison’s original invention. However, incandescents remain widely available on the market, but most are now filled with halogen gas to allow them to comply with federal energy-efficiency standards. Unfortunately, the federal standards were drafted in such a way that many manufacturers are meeting the new power limits by making their lamps dimmer. So it takes careful label reading and comparison-shopping to get a true replacement. Use the “Incandescent Replacements” table to ensure that the halogens you buy are just as bright as the old incandescents you are replacing. 

For example, if the new halogen bulb you are considering claims to replace a 75 W incandescent but only provides 900 lumens, it’s really more like a 60 W incandescent—and won’t give you enough light. General Electric sells a Reveal halogen bulb that claims to replace a standard 100 W incandescent using only 72 W, but it only provides 1,120 lumens. It is barely bright enough to replace a standard 75 W bulb, yielding almost no energy savings!

Many types of halogen bulbs cut power use by 25% to 30% but often cut light output substantially as well, barely improving efficiency.  Modified-spectrum halogens (the bulbs’ glass has a bluish-purple hue) are the worst offenders—avoid them. When buying halogens, look for infrared-reflective (IR) models with special low-e coatings that bounce heat back onto the filament while letting visible light pass through. This allows the best incandescents to deliver more lumens per watt. 

The old-fashioned incandescent lamps that remain legal to sell without halogen gas largely fall into particular niche product categories like three-way, vibration-resistant, and extremely bright (more than 2,600 lumens).  Avoid these products as well—there are more efficient choices.

A new, promising incandescent technology potentially doubles the efficiency and life of standard incandescents by using IR coatings to reflect bulb heat back to the filament, which makes it even brighter. These bulbs may achieve a remarkable 32 to 37 lumens per watt, compared to the 7 to 18 lumens per watt seen with typical incandescent bulbs. CFLs and LEDs are still more efficient than these new incandescents, but can cost more and have subtle differences in color quality.

Compact fluorescent lightbulbs (CFLs) are widely available in a range of sizes, prices, and light levels. They have miniaturized the technology found in typical linear fluorescent lamps, bending the tube into a small amount of space.  Thousands of models are now Energy Star qualified, and many utilities provide rebates for them.

Although they were once the only affordable energy-efficient lighting option, they come with caveats. CFLs do a reasonable job of rendering many colors, but they don’t render all colors well—and that’s easily noticed by people with particularly sensitive vision. Others have concerns about how to avoid mercury exposure if they get broken, and how to safely dispose of them. (Note that most analyses have found this to be secondary to their other environmental benefits, since their energy savings results in mitigating much greater mercury emissions from fossil-fuel power plants. See HP153, “CFLs & Mercury.”)

CFLs are also not usually dimmable, and can overheat in enclosed fixtures. This helps to explain why they are broadly used in some homes but rarely in all of a home’s light fixtures.

CFLs typically operate at about 50 to 70 lumens per watt and will run for about 8,000 to 18,000 hours before burning out. While they offer a low-cost way to save on lighting energy, they are increasingly being displaced by their better-performing cousins—LEDs.

Light-emitting diodes (LEDs) are quickly gaining ground as the most energy-efficient lighting technology. Although early LED models were bulky, expensive, and not very bright, those products have yielded to a new generation of quality products that use 10% to 30% less energy than CFLs, are easier to dim, and last far longer.

LEDs once operated in a similar efficiency range to CFLs, but can now achieve 85 lumens per watt across a wide range of light output levels, and best-in-class LED designs are headed to 100 lumens per watt—and beyond.

You can find comparisons of more than 17,000 LED lighting products, including information on lumens, watts, efficacy, color rendering index, and correlated color temperature, at lightingfacts.com.

The difference in color quality among incandescents, CFLs, and LEDs can be seen in the spectral distributions graph, which show how much of the light from each source falls within each wavelength of the visible spectrum, and compares that to the human eye’s sensitivity to each of those wavelengths (dotted curve). Note that incandescents (halogens) and LEDs both offer a continuous spectrum of colors, but incandescents tend to be dominant in the reds and fairly limited at the blue end of the spectrum. LEDs are often the reverse. CFLs, on the other hand, only emit light within certain portions of the visible spectrum, so can disappoint some users who are particularly sensitive to subtle color differences.

Matching Bulb to Application

Most home applications call for omnidirectional sources of light. “General service” bulbs work well in many kinds of table and floor lamps, enclosed globes, pendant fixtures, and other types of narrow light fixtures that mount close to the ceiling or wall. LEDs are a great option, but make sure they are truly omnidirectional. Many older models that have a snow-cone appearance shine most of their light upward.

Most down-lights are designed to accommodate particular reflector lamp shapes and sizes. PAR (parabolic aluminized reflector) lamps work best in deep ceiling cans and R (reflector) lamps work better in shallow ones. The diameter of the opening tells you what size of bulb to purchase. If the opening is a little less than 5 inches in diameter, a PAR 38 works well (the 38 refers to 38-eighths of an inch in diameter, or 4.75 inches). PAR 30 or PAR 20 bulbs tend to work better in smaller openings. Bulged reflector (BR) bulbs will also fit in the same ceiling cans, but tend to have very poor efficiencies, in part because their reflectors do not do as good of a job at gathering and aiming the light. The reflector lamp technology you choose is also application-specific. In general, CFL reflectors are not a good choice—their light is too diffuse. The most efficient halogen technologies can be a reasonably good choice, particularly IR halogens. LEDs are the most efficient choice, though still a bit expensive. Their directionality and dimming capability give them some natural advantages in this application, and their long lifetimes (20,000 hours or more) can be a plus, given the relative inconvenience of reaching and replacing many down-lights.

A wide variety of specialized lighting applications are not commonly served by the three major lighting technology types. If you want to distribute light uniformly over a very broad area, for example, it’s hard to beat linear fluorescent lamps for affordability and for even light distribution. Some manufacturers have begun producing linear LED “tubes” that can be inserted in place of these fluorescent lamps, but most still struggle to compete with the uniformity of linear fluorescent lighting at a reasonable cost. Linear fluorescent tubes that were 1.5 inches in diameter (T12s) have now given way to 1-inch-diameter lamps (T8s) and even 5/8-inch-diameter lamps (T5s), for improved efficiency and performance (see “Changing Fluorescents to LEDs” in this issue).

Efficient Lighting for Efficient Homes

Using the most efficient lightbulbs is especially important in zero net-energy (ZNE) homes or off-grid homes powered by renewable energy systems. The extra energy saved by using LEDs compared to CFLs, for example, is also cost-effective when compared to more PV modules and equipment for meeting the larger overall loads (see “Save on PV” sidebar).

LEDs also offer a wider range of color choices than CFLs, making them a more seamless integration with passive solar homes that rely largely on daylighting. For instance, using LEDs with a CCT between 3,000 K and 3,500 K in rooms with good natural light will help keep the light color more similar as the lights come on in the evening. Likewise, some LEDs shift their color temperature as they are dimmed, making them a good match with solar homes that get flooded with “warm” temperature sunlight at sunrise and sunset.

Purposeful Lighting

My recently completed ZNE house in Durango, Colorado, uses LEDs in almost every fixture, inside and outside. Linear T5/fluorescent lighting is used in the laundry room and master closet, and pin-based CFLs are used in one ceiling fan. Incandescent lamps are used in only a handful of aesthetically critical applications like the red glass and seashell mosaic pendant lamps over the kitchen island, the fully dimmable dining room fixture, and the small, wall-mounted reading lamps next to our bed, where the extra warmth of the light’s appearance is worth the energy-efficiency trade-off. Our brains interpret red light—similar to the light from a flame or a sunset—as a cue to go to sleep. By contrast, our brains interpret blue light from CFLs or most LEDs—similar to the light from a TV, computer monitor, or cell phone—as a cue to wake up.

While the lighting in most homes can consume 1,200 to 1,800 kWh per year or about 15% of total electricity use, our estimated lighting energy use is only about 400 kWh per year. The light source we used most widely in the house was the Cree screw-based 800-lumen LED, purchased for $10 to $13 apiece. We also relied heavily on a new type of Sylvania LED down-light that surface-mounts directly to electrical junction boxes in new construction, eliminating the need for a down-light fixture or its penetration through the insulation. These fully dimmable products were about $35 apiece, and distribute the light very evenly and unobtrusively into the room. High-quality Soraa LED MR-16 bulbs are used in low-voltage track light fixtures.

Besides its energy savings, our energy-efficient lighting looks warm and welcoming. On a public tour of the house last spring, the most common remark we heard from visitors was how pleasant and attractive the lighting was. We should never forget that a lightbulb’s primary purpose is to provide excellent light. No matter how much energy they save, they will never gain widespread acceptance unless they light up a room attractively as well.