I hate being wrong, but I appreciate being corrected by my friends so I don't continue to tell others the same wrong information. Let me explain.
A work colleague is getting photovoltaic solar panels installed and we got into a discussion of "net metering". Wait, don't stop reading now, I promise to keep this short.
"Net metering" is a simple rule that says, if the utility charges you, say 16 cents per KWH (kilowatt-hour) for electricity that you consume, then they must pay to 16 cents per KWH for any electricity you produce. It is basically a fair-is-fair or KWH for KWH trading between you and the utility.
But what happens if you produce excess electricity. If the power company can buy electricity for, say, 4 cents per KWH on the open power market, why should they pay you, say, 16 cents per KWH for your excess solar power.
So my understanding was that that the utility would only pay wholesale rates for excess electricity, say 4 cents/KWH. My colleague's understanding was that you got paid retail rates for excess electricity, say 16 cents/KWH.
It turns out that we were both right. Or more exactly, I was right 4 years ago (when my system was installed) and my colleague is right now.
Here is some data culled from my electricity bills for the last six years. The first thing to note is that I don't produce excess electricity every month, so there are a lot of holes in the data. The second thing is that I excluded some other data due to accounting issues (these bills are basically hand processed, the automated billing can't handle it).
Prior to 2010, the data shows I was paid a variable wholesale rate that was about 4 cents/KWH in 2009, and a little higher in 2008. This is a small fraction of the 18 or 19 cents/KWH that the utility was charging me for electricity when I bought it. Long story short, I was giving away my solar power to the utility for peanuts.
After 2010, the new net metering regulations required the utility to pay me retail rates which has been just below 16 cents for the last four years. This is the same rate (roughly) that the power company charges me, and four times what I was getting in 2009 for my excess electricity. This is not a huge sum of money (never more than $20 in a single month), but still a nice benefit for owners of solar panels and one more enticement for others to do the right thing and get solar panels...ya know, global warming, energy security, pollution, yada yada yada.
The kicker is this. You cannot make money from this system. The "credits" that appear on your bill in terms of dollars can never be paid out in cash. The money always stays with NSTAR, one way or another. Most likely you will use credits earned in the summer to help offset your bill in the winter, which is awesome. If you consistently over produce, your credits can be applied to someone else's bill, e.g. a family member or your church.
If you are like me, you've probably already switched over to CFLs and/or LED bulbs for their efficiency, but have one or two light fixtures where you just can't find the right bulb for the job. For me, that challenging light fixture is right above my desk as I am typing this.
The first challenge with the fixture is that it is a 3-way bulb fixture. You know the kind, one click to low brightness, second click to medium brightness, third click to maximum brightness, and fourth click to off again. The second challenge is that it has a relatively short harp (the metal piece that goes around the bulb and holds up the shade). This means that the replacement bulb has to be realtively short and the CFL 3-way that I purchased a few years ago never worked because it didn't fit. Not willing to use an incandescent, I have been using a 60 Watt equivalent CFL.
The image below shows the Switch LED to the right and a 3-way CFL to the left.
The most obvious difference is the height. The CFL is 6.5 inches long whereas the LED is 4.5" long. Importantly, this means that the LED bulb actually fits in my light fixture. This is fantastic because I have not had a proper 3-way bulb installed for about 4 years.
The next most impressive thing is the weight of the LED, 10.2 ounces (289 grams). That is more than twice as much as the CFL at 4.9 ounces (140 grams) and probably ten times heavier than an incandescent bulb.
Part of the reason for the high weight of the Switch LED is that it is liquid filled. This liquid pulls heat away from the light emitting diodes which is critical to keeping them cool which is critical to long life. This is a big issue with LED bulbs. Although LED bulbs are naturally much cooler than incandescent bulbs, the truth is that LEDs are much more sensitive to heat. As a result, many LED bulbs are not suitable for enclosed light fixtures. The excessive heat build-up for an LED in an enclosed fixture would greatly shorten the bulb life. Switch claims that their LED bulbs can be used in an enclosed fixtures which is great.
The real headline for this bulb is that it produces the same light as a 100 watt incandescent while using only 20% of the energy.
30/70/100 watt, incandescent
11/18/23 watt, CFL (shown above)
6/13.5/19.5 watt, Switch LED
So not only is the Switch LED more efficient than the incandescent, it is significantly more efficient than the CFL.
The other number of importance is the amount of light output which is measured in Lumens.
305/905/1300 lumens, incandescent
300/800/1100 lumens, Switch LED
So the Switch LED is a little less bright than a traditional bulb, about 15% less on its highest setting. But I don't think that is too noticeable. I don't have the numbers on the CFL since it was produced before the EPA started mandating lumen labeling on bulbs.
What's that, price, [cough, cough] you want to know the price? You might want to sit down first. Ah well, it was $45. Yes I know that is a lot more than the $2 for an incandescent, and more than the $14 for a 3-way CFL. However, there are some other things to consider.
Firstly, Switch just introduced a new line of less expensive bulbs, that are more like $20 per bulb than $50 per bulb. This new line isn't shipping yet, nor does it have a 3-way model. However, I think it is reasonable to expect a $20 3-way LED bulb within the next year. Secondly, these bulbs should last 25,000 hours or about 12 times longer than an incandescent. To do a little math, 12 incandescent bulbs at $2 each is $24. So if the LED price comes down to $20, the price is more comparable.
One more piece of math, there are 8760 hours in a year. A 100 watt incandescent bulb running for a year would consume 876 KWH, or (at $0.15/kwh) $131 worth of electricity. By contrast, the LED equivalent would only consume $26 worth of electricity. So if the price of the bulb plus electricity is considered, the LEDs are not as expensive as you might think. In fact, for heavily used bulbs, LEDs bulbs are much less expensive than incandescent bulbs.
To wrap things up, let's talk about the subjective aspects of the bulb. Personally, I like the look of the LED bulb a lot more than the curly CFL bulb. The light color of the LED is pleasing, it is instant on, and dimmable (not that you would with a 3-way). The light distribution pattern seems to be quite uniform, which is a weakness for some LEDs that are naturally more directional than an burning hot filament.
Overall, I'd say the Switch LED is a winner, once the price is down to $20 anyway.
For reference, the Switch LED number is A23WY1FUS27A4-R and the CFL is a LightWiz S23WL3 or H23327 bulb.
When my home was built in 1950, oil cost only US$2.77 per barrel. I know, I know, you are thinking everything was less expensive back then, and that is true. But even adjusting for inflation, oil in 1950 was only $26.46 per barrel. In these days of $100 per barrel oil, it is fair to say that by any measure, oil in 1950 was cheap.
So it should come as no surprise that when the front door was put on my 50's Ranch in Lexington, MA, it had almost no insulating value. The glass in the door is only single pane with an R-value of about 1 and the thin raised panels on the door are made of solid wood have have an R-value approaching 1 as well. By contrast, a 2×4 wall with fiberglass insulation has an R-value of about 13. So from an insulating standpoint, my front door is doing very little indeed.
If a picture is worth a thousand words, an IR image is probably worth two thousand words. In the above infrared image, the white portions are hot which is bad because that means the heat is getting outside the house. A couple of things are clear from these images. First, the storm door helps hold in some of the heat (although it is not nearly as good as the insulated walls around it shown by the blue color). Second, the storm door doesn't cover the cover the sidelite of the door and as a result, the sidelite has very little insulating value.
The view from inside the door tells a similar story. From inside the house, we should focus on the blue color because that indicates cold, which is bad. The image show the sidelite is dark blue which means it is less than 56°F and much worse than some parts of the main door which are yellow or green in color. Also notable is that the raised panels are very thin as can be seen from the blue color around the edges of the raised panels.
Due to the high cost of home heating oil and the "Global Hotting Up" thing I keep hearing about on the news, I would like to "fix" this door.
The Standard Solution
The typical "solution" to this poorly insulated front door is to buy a new fiberglass one with foam insulation and double pane windows. Frankly, I am not a fan of this "solution" because it would likely cost thousands of dollars (installed anyway) and be a relatively small improvement. To clarify this a little further, perhaps it is worth giving a little bit of background.
Background
In the world of insulation, there is something called the R-value which is a numerical value showing how well something insulates. A low value such as 1 is poor, and a high value such as 30 is good.
In the 1950's, when my house was built, walls had no insulation at all and had an R-value of 1. Around the time of the 1973 OPEC oil crisis, it became common to insulate 2×4 wall cavities with fiberglass insulation which achieved a much better R-13 value. This is also about the same value that a home like mine with blow-in cellulose insulation achieves. In more recent times, building codes often require 2×6 walls so that more insulation can be put in the walls to achieve R-19. That is some significant progress.
In the 1950's, windows were single pane and had an insulating value of R-1. Later, in response to the 1973 OPEC oil embargo, storm windows were added increasing the R value modestly to about R-2.5. In the modern times, double pane glass is the norm and offers an R-4.
R-1 single pane glass
R-2.5 single pane glass with storm
R-4 double pane glass
So in the modern world, it is normal to expect to see homes with R-19 insulation in the walls and R-4 insulation for the windows. People talk up these windows as if they have wonderful insulating qualities, but they just don't. Frankly, modern double pane windows are &^$%. Architects have access to SuperWindows with R-10 insulation but home owners can't even get windows with half that insulation value.
Here is what it is like putting a modern double pane window in a home. You start with an R-19 wall, cut a 3 foot wide by 4 foot tall opening and then shove back into the opening only a 1" thick piece of fiberglass. It is pathetic and we need to do better.
Replacement windows are one of the most oversold and questionable "investments" of modern times. Consider a home like mine that has functioning single pane windows with functioning storm windows yielding an R-2.5. The standard solution is to replace them with double pane windows and no storm with an R-4. This small improvement, from R-2.5 to R-4 will cost about $1000 per window (installed) which could never be justified by the energy savings. Of course, if the existing windows didn't have functioning storms, were very drafty, or didn't function well, the home owner may choose to replace the windows for those reasons, but not for the energy savings alone. Don't get me wrong, on new construction, double pane windows are really are definitely better than the old single panes plus storm. But if you have single pane windows with functioning storms, think twice before "investing" in double pane windows.
The Better Solution for the SideLite
A brand new Home-Depot insulated door would have an measly R-4 value. My goal was to exceed R-value that and spend less money to boot. The proposed solution is to build a storm window to cover the existing sidelite. The design has a two pronged approach. First, a new double insulated glass unit will be used and placed in front of the existing single pane, effective providing triple glazing with about R-6. Second, the lower part of the storm window would use 2" of rigid foam to achieve R-10 insulating value.
The above video shows how the storm window was created including a cool little animation from Pro/Engineer, the CAD software tool I used to design the pieces and virtually assemble them.
The first step was to create a wooden frame for the face of the storm window as shown in the above image. The lower portion has a wooden raised panel that mimics the look of the existing sidelite. The upper portion has a pocket cut out to a depth of 0.5" so that the glass can be installed inside.
The next step was to obtain a piece of double pane glass. This was the part of the process that had me most worried. I have purchased single pane glass many times, but was not sure how to go about getting double pane glass. It turns out that you can buy double pane glass in any size you want and it is very easy.
I called down to a local glass shop (Century Glass in Waltham, MA) and told them I wanted a 42 3/4×9 3/4×1/2" pane of low-e glass. They placed the order with Guardian Industries (Webster, MA) by converting my request into a part number, ICNU70CL1260C.i3.1TC+6.4+3.1TC. I would love to know what all that means. It is pretty clear that the 3.1 is the thickness of the glass in millimeters, and 6.4 is the spacer between the glass panes in millimeters. The resulting glass thickness is 3.1+6.4+3.1=12.6mm or 1/2". The part actually came in at 0.560" but close enough. The glass panel cost $65 and took about one week for delivery.
A bead of clear silicone caulk (GE5000, 0 77027 05000 4) was put into the window frame and the glass was then pressed into it. An additional bead of silicone was added to the back of the glass. The glass was held in place by a secondary frame and 14 #8 stainless steel wood screws that were 3" long. Later, additional #8×1.5" stainless steel screws will be used to hold the storm window to the house. Including shipping, the screws cost a staggering $25 from McMaster-Carr.. I could have done this for much less money using zinc plate screws from Home-Depot but I just could not bear the thought of these screws rusting in a few years.
Joyfully, for the lower portion of the storm window, there was room for 2" of rigid foam. This was cut to the right size on a table saw. I could have just left the foam as it was, but I didn't like the fact that the foam could be easily damage if the storm window was ever removed from the house for any reason, e.g. maintenance. So I cover the foam on five sides with 1/4" thick plywood for good measure. The plywood was bonded in place using Loctite PL300 Foamboard construction adhesive (0 79340 68650 2) which advertises "Won't melt or burn foam."
The foam and plywood assembly was bonded to the back of the raised wood panel again using the Loctite adhesive.
The completed assembly was primed and then painted three coats Behr Premium Plus Exterior Satin Enamel (Base 9340, 267413187349) custom blended to match the door color (wineberry). The cost of a quart of paint was about $25. Yep, costs are starting to add up.
In order to be effective, the storm window needs to seal against the existing window frame. Since I wanted the frame to be removable, I decided to attach weather stripping to the storm window rather than caulk it in place.
The weatherstripping used was Frost King V25G and cost about $5. The "D" shape of the foam is very compliant and allows it to fill a wide range of gap thicknesses.
The completed storm window was screwed into the existing window frame and seals nicely. Prior to installing it, I measured the inside temperature of the sidelite which was a chilly 55°F. After installing the storm window and waiting an hour, the temperature increased to 66°F, showing the value of the added insulation which the storm window provides. Some day I will again rent the IR camera from Home Depot and hope to show some impressive improvement from the old IR pictures. But it is not worth the $45 rental just for that one picture.
Wrap Up, Thoughts
I am very pleased with appearance of the storm window, its "better-than-commercially-available" insulating qualities, and its cost of just over $100. However, I have some reservations about the economic value of the exercise.
The insulating value of this storm window is perhaps about R-8 which is still lower than the surrounding walls with R-13. More troubling is that all this time and money was spent to improve just about 6 square feet of surface area. I have basement walls that could benefit from added insulation and with the same $100 I spent on the storm window could have purchased enough 2" thick pink foam to cover 80 square feet. In other words, I could have gotten more "bang for my insulating buck" elsewhere in my home.
But I like to think more optimistically about these things. I have fixed what had been the least insulated part of the first floor of my home. That is one good step in the right direction and a slight hedge against the inevitable day when oil reaches $400 per barrel.
UPDATE: JANUARY 25, 2015
It's been two years since the original post and I've finally gotten around to renting the IR camera again, and the results of the modifications to the sidelite are impressive.
Unfortunately, it looks like I used a different color palette for the false color images and some of them are a little washed out, but I think the main points are still clear.
Looking at the image below, at the lower right panel of the door, it is clear that the rigid foam insulation has done its job. That area looks as good or better than the wall. Unfortunately the double paned window above it as washed out in color and not much can be observed.
On the inside, the impact of the double pane window can be clearly seen. On the door windows (top right) there is a very dark color indicating cold. On the sidelite (left) the window glass is a much lighter color indicating that it is warmer.
The most striking difference can be seen in the last image. The wood panel in the sidelite (lower left) is clearly much warmer than the raised panels seen on the door on the right.
However, while I'm please with the improvements to the sidelite, the main door has a larger area and is still clearly very cold.
