Residential Photovoltaic, Efficiency First

If you are thinking about photovoltaic generation, absolutely your first consideration should be maximizing efficiency for all your electricity use.  It just doesn't make any since to pay $5,000 / KW to install your own (or $10,000 / KW for installed photovoltaic) when an extra PC that you don't need left turned on consumes 2 - 3 KWH / day.

Generally, I'm not a fan of consuming just to be "green."  There is something contradictory about protecting the environment by throwing something perfectly good into the landfill just so you can buy something green to replace it, but there are some exceptions.  When the continued use of anything puts more load on the environment than its green replacement would, then I feel justified in replacing it ASAP.  And energy efficiency is one of those areas - continued use of fossil fuel seems worse than dumping my old light bulbs and manufacturing new ones.

Efficiency in Water Heating

If you've got sunshine for PV, you've got sunshine for solar thermal hot water heating.  Don't even think of adding PV to generate electricity until you've got solar how water heating.  A typical solar hot water heating system that costs only a few thousand dollars can cut your energy consumption by more that 5000 KWH a year as compared to electric water heating.  Solar thermal water heating is 10 times more effective at reducing your energy use, carbon footprint, and utility bills, than solar photovoltaic electricity generation. Do it first.

In the background of the picture at right you can see some of my photovoltaic modules during construction, but in the foreground you can see my existing solar water heating collectors.

Efficiency in Lighting: Compact Fluorescent Light Bulbs

Almost every use of traditional incandescent bulbs can be replaced by using compact fluorescent light bulbs.  CFL bulbs are slightly more expensive to purchase, but the payback is way faster than the payback associated with PV generation.   Prioritize the bulbs you change out: bulbs you use a lot and high wattage bulbs should be changed first.  I replaced almost every bulb in my house, but probably that was overkill from a strict financial payback perspective. 

These mini-spiral CFLs are available in incandescent-equivalent wattages from 20 to 150.  Anything larger than incandescent-equivalent 100 watts is slightly larger than a traditional globe incandescent.  You can even get 3-way multiple wattages bulbs for lamps with 3-way switches.

The table below shows the light output from common incandescent bulbs and equivalent sizes for CFL bulbs.  If you want task lighting for reading or working, choose incandescent-equivalent wattages of at least 75.

 

Incandescent-equivalent watts	Actual CFL Watts	Light output (Lumens)
40	9 - 13	450
60	13 - 15	800
75	18 - 25	1,100
100	23 - 30	1,600
150	30 - 52	2,600

Many other styles of CFL are commonly available and more styles are coming onto the market every day.  The majority of CFLs are designed to look identical to the incandescent light bulb version.  If you have decorative applications, ceiling fan bulbs with candelabra bases, incandescent floods, even outdoor lighting, you can probably find a CFL to handle the situation. The table below identifies the most popular CFL shapes that are available.

 

Bare Products		Covered Products			Reflector Products
Mini-Spiral or Twist	Tube or Universal	Incandescent/ A-line	Globe G25, G30, G40	Candelabra, Post or Bullet Shape	Indoor and Outdoor R20, R30, R40, PAR38

Some people report premature failure of CFLs when used in ceiling cans, probably because CFLs may not do well in high heat environments, and when a CFL is installed "upside down" all the heat goes straight to the electronic portion of the bulb - right were you don't want it.  I haven't ever had this problem myself, but it has been reported to me.

For recessed ceilings lighting in "cans" I prefer the traditional spiral CFLs to CFL bulbs packaged as floods.  The advantage is they are slightly less expensive, slightly more efficient, and you have more choices of wattages.  But to make them work well in cans, you have to replace the flat black "reflector" in the can with something shiny. 

Just remove the trim ring and "reflector".  Usually the reflector is matt black.  Use a high quality metallic spray paint to paint just the reflector, not the trim ring itself metallic silver or metallic gold.  Choose gold for a warmer light, silver for a cooler light color. 
 

There is another huge advantage to CFL bulbs, they last years and years.  A traditional incandescent light bulb it typically rated for an average life of 750 hours to 2000 hours.  CFLs are rated for an average life of 10,000 hours.  After you've converted to CFL bulbs you will not be replacing burned out light bulbs very often.  I haven't had to change a single CFL in my house yet, and I started swapping them in several years ago.

Dimming and CFLs

Dimming and CFLs don't mix.  If you have dimmers, you will need to get rid of them as you convert to CFLs.  I'm not trying to ruin your romantic mood lighting, it just isn't electrically compatible with CFL bulbs.  There are some new CFLs coming onto the market that claim to be compatible with dimming, but I've found them imperfect .  Also, be aware that dimming an incandescent bulb saves very little electricity, so don't think by keeping some regular bulbs dimmed you are being energy efficient.

Low Voltage Halogen v. CFLs

If you have low voltage track lighting with 12 volt bulbs there isn't any CFL option available.  There are some emerging options with LED bulbs, but I can't recommend you try any yet; they are very expensive and there are compatibility problems with most 12 volt fixtures.

There is some good news if you have these bulbs in your house; although they are not nearly as efficient as CFL bulbs, there are about 3 times as efficient as traditional incandescent bulbs.

Special Applications - Get Creative

You may have special lighting applications, maybe you want lots of Holiday lights, maybe you have some architectural lighting, or need some outdoor lighting - you don't have to give up on energy efficiency.  For example, LED holiday lights are now available that consume just 10% of the electricity of conventional holiday lights.  They may cost a little more to purchase, but the payback is still better than the photovoltaic generation you are considering.

Whatever the special lighting need you have, someone has figured out a way to solve that need with an energy efficient solution.

CFLs, Mercury, and Disposal

Despite their substantial energy saving benefits, compact fluorescent light bulbs (CFLs) present a unique challenge for the environment. CFLs contain a very small amount of mercury sealed within the glass tubing.  Mercury currently is an essential component of CFLs and is what allows the bulb to be an efficient light source. No mercury is released when the bulbs are intact or in use.

The US Environmental Protection Agency says if you break a CFL bulb, take special precautions cleaning it up: vent the room, put all the debris in a sealed plastic bag, wipe the area down with damp paper towels and seal the paper towels in a plastic bag.  Dispose of everything  as suggested below.

Many stakeholders, including solid waste departments and mercury-reduction advocates, are working to keep large accumulations of bulbs out of landfills.  Check with the agency that handles your garbage for specific instructions on how to dispose of them.  On Kauai, our landfill does accept fluorescent bulbs.

Efficient Fluorescent Tubes Too

The old standard for fluorescent tube lamps was T12.  These 1.5" diameter lamps are still better than incandescent light bulbs, but are the least efficient fluorescent tube lamp in common use.  Generally T12 lamps are 25% less efficient than T8 fluorescent tubes.  T8 bulbs are smaller at 1" in diameter, but do require different fixtures with the correct electronic ballast.

If you use existing T12 lights a lot, it is worth upgrading to T8 bulbs and fixtures.  And certainly if you are installing new fluorescent tube fixtures, avoid T12.

(A new standard for even more efficient fluorescent tube lighting is on the horizon.  T5 fixtures and T5 bulbs, 5/8" in diameter, are about 15% more efficient that T8 units.  T5 bulbs and fixtures are not yet generally available in the US.)

Efficiency in Appliances

Refrigerators, dishwashers, and other appliances use a lot of the electricity in your home.  Before paying big bucks for photovoltaic generation, be sure all your appliances are as efficient as possible.   If you are ready to spend thousands of dollars for photovoltaic generation, trust me, you will get more bang for your buck buying the very most efficient appliances you can.

All major appliance are required to have a tag, like the one at left, showing how much energy they use.  Pay attention to the annual KWH usage when comparing the various models you are considering.  If you live on Kauai, don't pay attention to the annual cost to operate the appliance - it is based on national average rates - multiple the annual cost by 5 to get a good guess about the actual cost to operate the appliance here.

You can also look for the Energy Star logo.  This logo is reserved for the most energy efficient appliances.  For example, ENERGY STAR qualified refrigerator models use at least 15% less energy than required by current federal standards and 40% less energy than the conventional models sold in 2001.  However some manufacturers also load up these top models with expensive features.  The Energy Star logo is no replacement for checking the EnergyGuide label.

Refrigerators

Did you know refrigerators consume the most energy of all the household appliances? Of course; they’re always on. All new refrigerators use half the energy of similar models built 12 years ago. Highly efficient Energy Star® models can cut that by another 20 to 36 percent. The top freezer models are the most efficient, using 7-13 percent less energy than the side-by-side. Bottom freezers are slightly less efficient than the better top freezer models.

Freezers

A manual defrost freezer uses 35-40 percent less electricity than one with an auto-defrost option. Eliminating the auto defrost will also reduce the freezer burn effect.

Dishwashers

Most of the energy used by your dishwasher is for heating the water. The circulation pump and dryer account for the rest. Energy efficient dishwashers reduce the amount of water used.  This reduces the amount of energy used to heat the water.

Some models also include sensors to determine length of cycles or completion of cycles that can reduce the water needed to complete the wash cycle. Energy efficient dishwashers also include airdrying options that allow you to dry the load without additional heat, saving additional energy and money.

If you have solar thermal hot water heating, the difference between energy consumption of efficient and inefficient dishwashers will be much less.
 

Clothes Washing

Conventional clothes washers will consume 45-60 gallons of water per load. Hot water consumed by these machines typically account for 26 percent of your home’s hot water bill. An energy efficient clothes washer will use only one third as much water. This can reduce your cost for water, water heating, and waste disposal. New machines with high-speed spin cycles also reduce the time needed to dry your clothes, saving more energy.

There are two styles of washers on the market; top-load and front-load (or tumble action). In a top-load model, the tub is filled completely, immersing the clothes in water. In a front-load model, only the bottom of the tub contains water. The clothes are tumbled into water instead of immersed, requiring significantly less water and energy for heating water.

A few top-load washers take advantage of new technology to save water. Instead of filling the tub for the rinse cycle, these washers use a high-pressure spray to remove the soapy, dirty residue, saving many gallons of water.

Energy Star® clothes washers include both front and top-load styles, and use nearly 50 percent less water and 30-40 percent less energy per load. Some other characteristics of Energy Star® washers are better extraction of water due to a high-speed spin cycle, sensors to control incoming water temperature and high-pressure sprays used for rinsing.

If you have solar thermal hot water heating, the difference between energy consumption of efficient and inefficient washing machines will be much less.

Other Appliances

Your appliances really do consume a lot of electricity.  The chart below shows the average annual electricity use of different appliances.

Flat screen LCD TVs (but not Plasma TVs) consume a lot less electricity than old fashioned CRT (picture tube) TVs.  Get that new flat screen TV you want and save the environment.

So surf the 'net and check out the energy consumption of all your major appliances model by model.  Replacing older models will probably pay for themselves.

Where Efficiency Meets Conservation:
Turn Stuff Off

We have lots of electric things in our homes and most are plugged in all the time: toaster ovens, paper shredders, power tools, lamps, fans, and blenders.  These electric items are typically identified either because they make light, have motors, or make heat.  These electric items consume electricity only when switched on.  There is no penalty to leaving these items plugged in when not in use.

We also have lots of electronic items in our homes: TVs, computers, VCRs, and lots and lots and lots of items that plug into AC wall current using a transformer.  The transformer, AKA AC adapter, AKA power brick has become ubiquitous. Your iPod, your digital camera, your cell phone, your PC's speakers, your wireless router - all these items are probably plugged in to AC via a transformer.

Each of these little power bricks is using a tiny amount of power as long as they are plugged in, even if the appliance they support is off, even if the appliance isn't even plugged into them.  The power they consume really is tiny, a good approximation is 1 watt.  But if you leave your cell phone charger plugged in all the time that 1 watt is multiplied by 24 hours a day and 365 days a year - that's 8.5 KWH a year.  Depending on the size of your photovoltaic installation, that 8.5KWHH might represent an entire days photovoltaic electricity generation.  Considering how much you expect to send on your PV system, would you be happy to learn that you give up an entire days output?  Maybe not.

Obviously you can't unplug your DVR if you expect it to record your favorite TV shows on schedule.  Any you may really want to leave your cell phone charging all the time so it is always full charged when you need it.  On the other hand, it may be trivial to unplug your iPod power brick when not in use.  Unplugging your electronics when not in use won't save one twentieth as much as upgrading an old refrigerator to a new energy efficient one so get your priorities straight.  But it doesn't cost anything to unplug electronics when not in use but the effort to bend over and the effect is multiplied for every electronic item you can unplug - it does add up.

Radical Demand Reduction

The chart above says an average dishwasher uses 600 KWH a year and an average clothes dryer uses more than 1000 KWH.  Does that mean you will save 1600 KWH annual if you get rid of your clothes dryer and line dry all your clothes and pitch your dishwasher and get busy washing dishes in the sink?

Yes and no - probably more no than yes. Trying to figure out the all-in impact of apples v oranges is almost impossible. And these two examples are perfect illustrations. 

Apples v. Oranges

A dishwasher uses hot water and then adds more heat to actually heat the dishes enough to kill germs. You can’t get the water nearly that hot if you are hand washing, even if your hands could take straight 120F 100% hot water from the tap, that isn’t nearly as hot as a dishwashing machine heats the water. You’re welcome to decide you don’t want or need the extra features, but you can’t make a simple statement about energy conservation without also making it clear you are getting two different results.

Exactly the same apples v. oranges thing happens with clothes drying. In high humidity clothes dry much more slowly, so slowly in fact that several varieties of mold can start growing on them. Not a problem for me, but someone with mold allergies would have a big problem.

But How Many KWH is an Hour of Your Time Worth?

It takes me less than 60 seconds to move a full load of laundry from the washer to the dryer and turn it on. It probably takes me 20 minutes longer to hang it on the line and then retrieve it when dry. Before you can say line drying uses less energy, you have to know what I did with that 20 minutes of my life I didn’t spend doing laundry. Maybe I used the 20 extra minutes so I could bike to work instead of drive. Maybe I did some gardening to grow food. Maybe I just watched TV and got fat. The all-in KWH comparison would have to assign a KWH value to that 20 minutes of spare time, and that is impossible.

So I can compare two different clothes driers and make an accurate statement about the different energy consumption of the two models. And I can also make an accurate statement about the energy consumption of either model to performance a specific task, e.g. doing a load of dishes in my dishwasher uses about 2 KWH or drying a load of heavy cotton towels in my clothes dryer consumes 3 KWH.

What I can’t factually say is you will SAVE 3 KWH if you hang your clothes on the line instead of using your electric dryer.

So Make Informed Choices

Know what the energy consumption of your appliances is, and know what your KWH rate is so you know how much it costs every time you use your dishwasher or dry a load of clothing.  Know how much the energy cost equivalent is for driving to town.  Then you can make some good decisions on how to spend your energy budget.

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Page lasted updated April 06, 2008