Mapawatt blogs

What is Watts per kilogram?

ckmapawatt — Tue, 09 Jan 2018 02:30:31 +0000

Watts per kilogram (W/kg) is a way to normalize a cyclist's power output, Watts (W), by their weight in Kilo-grams (kg).

Training Peaks has an excellent article on why you should focus on Watts per Kilogram:

"For the cyclist that rides on completely flat roads or trails, W/kg isn’t very important. If the terrain is flat, then the rider with the highest absolute power will almost always go faster. However, for athletes that ride regularly in hilly terrain, compete in events with climbs, or want to be more proficient sprinters, W/kg should be a primary focus. Unlike many of the other metrics cyclists track, W/kg is relatively straightforward to improve. There are only three ways in which you can affect some change in your W/kg. They are as follows:

Increase your power output while keeping your weight constant.
Keep your power output constant while decreasing your weight.
Increase your power output while also decreasing your weight."

https://cyclingtips.com/2017/06/just-how-good-are-male-pro-road-cyclists/

http://home.trainingpeaks.com/getmedia/a4f43215-cd08-4a58-93b8-b9c880172...

https://www.trainingpeaks.com/blog/power-profiling/

The Perils of Home Automation

ckmapawatt — Sun, 11 May 2014 23:05:24 +0000

The following guest post analyzes how recent innovations in home automation could impact us in areas we may not realize.

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Speculative fiction commonly depicts bleak visions of the future, but the content is typically reactionary to current, real-world events. Such fiction examines the duality of technology, which is an integral part of contemporary society, but also a constant source of anxiety. Where this sort of literature really stands to benefit humanity is where it invites speculation about the sustainability and sensibility of our societal infrastructure. In other words, this sort of fiction begs the question: “what could happen to the world if destructive modern trends persist?”

What’s more than a little troubling is that with recent news stories such as the Edward Snowden whistle blowing fiasco, or even the recent news about Google purchasing the smart technology developer Nest, it seems that dystopian science-fiction tropes of decades passed seem to becoming (at least partially) political crises manifest in the real world.

A common theme in dystopian science-fiction is that the misapplication of technology itself could bring about the end of civilization as we know it. These were trends that seemed to have been born out of anxieties that were mounting around the time of the Industrial Revolution at the turn of the 19th Century. Certainly, the English writer H. G. Welles explored these ideas through his written works, notably In The Time Machine and The Sleeper Awakes, both of which deal with late 19th century English protagonists who end up catching a glimpse into future societies that are morally and ethically inequitable.

World renowned psychoanalysts like Sigmund Freud wrote extensively about the psychological impacts of a society that was becoming increasingly dependent upon machines. Freud, like Ernst Jentsch before him, wrote extensively about “uncanny” feelings that humans typically seemed to have in response to automata, dolls, factories...in other words, a prevailing view held by psychologists at the beginning of the 20th century was that people felt a certain level of revulsion in response to both non-human entities which either resembled or behaved like humans, and conversely, that people felt ill at ease seeing the human body relegated to in-human, mechanical functions. The proliferation of factories and machinery seemed to induce some sort of collective identity crisis.

Science-fiction took a markedly different turn after World War II. The United States bombing campaigns of civilian Japanese communities demonstrated that if some of the world’s most innovative minds were recruited, they would be capable of using their genius towards destructive ends...ends which were more destructive than anything the world would have been able to imagine up to that point. The world was no longer grappling with abstract paranoias about misapplied technology, but had in fact caught a glimpse of how potentially destructive the technology could be.

And because of how the United States prospered after World War II, industry and the development of technology, for both military and domestic applications, thrived. Someone who wrote wonderful, although deeply disturbing, fiction in response to these developments was Ray Bradbury, who wrote The Martian Chronicles at the height of the cold war era, which included the short story August 2026: There Will Come Future Rains. Among the many things that Bradbury wrote about were homes of the future that were fully automated, which could cook meals, light cigars, and speak in perfect English..but unfortunately, the human race had been annihilated during a nuclear attack. Bradbury took jabs at both the gratuitousness of luxurious technologies in the United States at the height of the cold war era, and the potential destructiveness of misapplied technology.

Nowadays, consumers are becoming increasingly conscientious about their energy consumption habits, and are looking for companies to develop sustainable methodologies which don’t deplete natural resources and don’t introduce other pollutants or toxins into the environment. While this is good fundamentally, it has created for a situation where consumers also have to be cautious about “greenwashing”--companies perpetuating falsehoods about how “green friendly” their products are purely as a marketing strategy.

It becomes especially worrisome in the case of home automation technology, where the potential security risks could outweigh the convenience. Part of the concern is that if you compare the features offered by the newest home automation technology, one of the biggest selling points seems to be giving people the ability to set their home security settings, control their home lighting and entertainment systems, and even monitor closed circuit cameras from tablet computers and even mobile phones. Suddenly, a misplaced or stolen phone could represent a key to your entire home security system and whatever other systems the phone is set up to control - not a comforting thought!

It’s worrisome also because, with Google now a major player in the home automation field and interested in placing their devices in every home, they will be able to collect even more personal data about everyone than they have ever had previously - even if it’s just data about utility usage like electricity and water. To what end will they use that data? We’ll leave it to contemporary science-fiction writers to contemplate that. But consumers must be cautious, lest they make themselves vulnerable under the guise of convenience

Category:

Energy Monitoring and Control

Moving towards zero net energy home - 2014 edition

ckmapawatt — Wed, 05 Feb 2014 13:24:26 +0000

Way back in 2010 we put up the post on 10 steps to build a zero net energy home. We figure it was time for an update! For the pic above to be zero net energy, it probably needs solar panels on the othe side of the roof and I hope the glass doors are double (or triple!) pane, but we hey, we liked the picture. The following guest post was written by Brandon Engel. You should follow him at @BrandonEngel2.

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As consumers are becoming increasingly conscientious about reducing their carbon footprint, and the the state of the economy is forcing most homeowners to reconsider the sustainability of their day to day habits, we’re seeing more and more interest in “zero net energy” homes - houses which produce more energy than they use, and emit no carbon annually.

The idea is that while homeowners will typically pay a small fee to the utility company to stay on the grid (commonly in the ballpark of $10 a month), zero other energy expenses will be incurred annually, and what’s more, homeowners might even be able to monetize their surplus energy by selling some back to the grid (mapawatt note: this is commonly referred to as net-metering).

There’s been a lot of discussion in the mainstream press about zero net housing recently, too. The humanitarian organization Habitat for Humanity just built one for underprivileged occupants. It’s an application of technology that stands to benefit the environment, and homeowners at all income levels.

If you’ve been thinking about building your own zero net home, and would like to see dramatic reduction of your carbon footprint by the end of the year, here are a few practical tips for getting started.

The first thing you’ll want to look into are tax incentives (such as those offered in Colorado). Ultimately, you’re looking to save a tremendous amount of money in the long run if you build a zero net home, but what’s better is that you may not even have to foot the bill for all of the initial hardware/installation. In most states throughout the U.S., there are federal and state subsidies that you might be able to use to partially finance your build. If you purchase and install photovoltaic panels, for instance, you could be eligible for as much as a 30% federal tax incentive. If you are investing in having a property built right now anyways, the difference in the initial overhead could be quite negligible - especially if you account for the tax incentives, rebates, and, of course, the fact that you will not incur any other annual energy expenses.

Once you have your budget laid out, the next step is building the envelope. Just remember: insulation is key. You want to retain heat in the winter, and you don’t want excess heat finding its way into the house during the summer. You’ll want sizeable studs for your wall, potentially as big as 2” by 6”, just to achieve optimum insulation within the wall cavity itself. The next step, then, is plywood sheathing around the wood panels, and a plastic air/moisture barrier to cover the entire house, from the foundations to the exterior walls to the rooftop itself. After that, everything should be covered in up to four inches of Polyiso plastic foam. Then the roof itself will need a little more attention: it’s best to further insulate it with plywood insulating foam composite, to ensure that the house will seal heat. Another thing you’ll want to be mindful of is your duct work. Make sure that all the ducts in the house have been taped and sealed to ensure that they are air-tight.

Of course, let’s not forget one of the most important steps of all, a source for renewable power. You want your house to feed off of power sources which are entirely renewable. Obviously, this eliminates gas and oil. What you want is something that will generate electricity in a way that does minimal harm to the environment. The logistics of your plan will have to depend largely on the conditions of the land surrounding your property. In certain areas, solar panels and wind turbine power generators are a viable solution. Photovoltaic panelling can be installed on the roof of your property, or on a two-axis tracker set-up near your home. A ground-source heat pump may make sense for certain homes, but they certainly don’t work universally (especially not in a leaky house) however this could be the best alternative for anyone living in a particularly cold climate. Location is always critical, and while solar and wind turbine power might make the most sense for some owners, others will have to rely on other sources of clean energy. Thankfully, there are companies who provide efficient energy in certain regions. For instance, people living in Illinois might try Choose Energy , while residents of Texas might consult TexasElectricityProviders.com.

One of the most pressing issues for consumers is knowing how much power is actually needed to run a home with reasonable amenities, and what sort of power you’ll need to produce via solar, wind, or geothermal energy to keep your house operational. Residents of the U.S. have an average of about 110 volts fed into their homes off the main grid. This power can be augmented by solar panels which absorb DC power from the sun, convert it into AC power using inverters, and pump that energy either back into the house are a bank of back-up batteries which store power for emergencies. Another approach is to simply have the solar panels connected to the inverter, with the power being pumped directly back into the house.

And how much power can you expect to harness from, say, solar panels? South African vlogger Martin Lorton, for instance, says that he has a 2,250 watt solar panel array on the roof. He says that, on a sunny spring day, he generates in the ballpark of 13 KWH of energy. On an overcast day, he might generate closer to 7 kwh. Lorton recommends using special monitoring software, so that you can accurately gauge the efficiency of your solar panels throughout the course of the year. Some experts are going as far as to say that you could use 60% less energy than you would with propane (and you know how much of a carbon footprint propane leaves behind). (mapawatt note: if you're new to solar, check out our Residential Solar PV educational post).

So, zero net housing could perfectly suitable for occupants, as long as they are diligent about monitoring their power supply and are conscious of how their systems faire in different weather conditions. Homeowners can now enjoy greater levels of autonomy than ever before, and save money while reducing the amount of pollutants they release into the world. Perhaps in a few decades time, zero-net houses will become the standard. Just imagine the benefits that could yield, not only for our bank accounts, but for the very earth itself…

Category:

Sustainable Home Building

Google back in the Home Energy Game

ckmapawatt — Thu, 16 Jan 2014 17:50:11 +0000

Back in 2011 it was 4 months after we covered Google shutting down its PowerMeter service that we first covered the Nest Thermostat. Now, things have come full circle with Google acquiring Nest and getting back in the home energy game. From the GTM article:

"Google has also been toying with its Android @Home concept to connect smart devices onto an internet-of-things platform. But it hasn't publicly announced much since the idea was first announced two years ago. Nest's products may add some muscle to that effort.

As the story went to press, GTM analysts were busy (jokingly) speculating on what "unloved" products in the home Google will help Nest tackle next.

- Extension cords
- Circuit breakers
- Door knobs
- Plug outlets
- Sprinklers
- Exit signs"

Nest recently announced a smoke alarm as its second product after the thermostat, so I think in the future we wont refer to Nest as a "home energy" company, but rather as a "home product" company that enhances and connects devices we use in our daily lives at home. In fact, it seems that a dedicated "home energy" product market is going away, and all devices related to home energy are going to be bundled as part of a "smart home" or "home security". What's good for the goose is good for the gander.....

Tags:

nest thermostat

Google Nest

Category:

Heating and Cooling

Programmable Thermostat

Sustainable Flooring Options

ckmapawatt — Sun, 29 Dec 2013 16:19:24 +0000

The following guest post is written by Chris Long from Home Depot. My plan in the next year and a half is to research and eventually build (or refurbish) a home. A large part of that will be picking a sustainable and cost-effective flooring method. I am from Calhoun, GA, which is right below Dalton (the carpet-capitol of the world!) and is a very large flooring center in itself, so flooring has been under (and around me) my whole life! In fact, the book that set me on my sustainability journey in 2004 was Mid-Course Correction by the CEO of a carpet company, Ray Anderson. Ray passed away in 2011, but I was fortunate to be able to hear him speak in person shortly before that (see my blog post on that here). In my current townhome we have engineered hardwoods, and I'm not a big fan. They dent way too easily and we'll probably have to replace or resurface before we move. If we have to replace them after having them less than 10 years, I would say that's not very sustainable. What's your experience with different flooring options?

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You may not realize it, but every day one of the greatest platforms for sustainable ecological impact is right under your nose... and your feet! Eco-friendly flooring has many advantages for not only the environment, but also your family's health.

To avoid respiratory and other health problems, make the switch to greener floors. According to the Environmental Protection Agency, a variety of volatile organic compounds (VOCs) are commonly emitted during the installation of flooring and may remain in the air for years. These even include carcinogens like formaldehyde and benzene. Carpeting is often additionally treated with toxic chemicals to ward off insects and moisture.

Sustainable floors are made from recycled products. Why waste resources when plenty of quality materials are waiting for a home?

They're recyclable too. Over four billion pounds of carpet enter the U.S.'s solid waste stream every year, according to the EPA. Reusing and downcycling can easily avoid this toxic dumping.

They're not produced by fossil fuels. So many industries are dependent on oil, but these resources are not going to last forever. Green flooring materials are produced with natural and renewable means instead.

They last longer. With the proper care, green floors can last a lifetime.

They look great! Besides impressing the neighbors with your savvy environmentalism, eco-friendly flooring offer an earthy and natural feel.

Considering redoing the flooring in your home? Check out the following healthy, eco-friendly materials:

Hardwood. Elegant and classic, wood floors have a popular aesthetic while contributing to a natural sustainability. Look for wood harvested in your region, such as maple and oak. Most importantly, ensure that it is certified by the Forest Stewardship Council (FSC). FSC-certified forests regenerate their trees and protect the biodiversity within. Check for reclaimed or engineered wood to add a recycled edge!

A factory finish on the hardwood will leave the toxins out of your home. Hardwood can be installed without adhesives, but if you do go that route, look out for VOCs.

Bamboo. Harder than maple or oak, bamboo floors are as tough and long lasting as wood gets! Bamboo is naturally resistant to moisture, mildew, and insects. It's also a very renewable resource since it grows abundantly and quickly.

Ceramic or glass tile. For a classic kitchen or bathroom, look for tile made from recycled materials. One big advantage to using tile is its abundant variety of colors and eclectic patterns.

Linoleum tile. Natural linoleum is commonly confused with synthetic, unsustainable vinyl - don't be fooled! Tiles can be installed like puzzle pieces with no adhesives required.

Cork. Softwood flooring? Most definitely! Cork is particularly durable and recovers well from wear and tear. Many people enjoy the rugged look that results. The natural elasticity of cork lends itself to a very comfortable floor with good insulation and hypoallergenic advantages. Cork floors are naturally fire, dust, and insect-repellent. And much like bamboo, cork bark regrows rapidly in the forest.

Green carpets and rugs. Starting to think you have to fully abandon the cozy, insulating comfort of carpet? Don't worry; there are many green – and beige, and blue, and multicolored woven - options!

From the beginning of carpeting's life until the bitter end, consider its environmental impact:

What's it made from?
Carpets are most commonly made from nylon. Like anything else, natural, biodegradable materials from renewable sources are best. Look for materials like: sisal, seagrass, coir, organic cotton, jute, organic wool and bamboo. There are also recycled options, like carpet made from plastic bottles!

Does it contain VOCs or other toxic chemicals?
Natural materials can still be treated with toxic chemicals. This is particularly true of the often-unconsidered carpet backing and padding. Look for natural materials here too, especially including words such as "non-synthetic" and "untreated." The backs and pads should be attached either by sewing or glued with adhesives that are non-toxic.

How and where was it manufactured?
Research the specific companies who produce the carpet you are interested in. What is their commitment to their environmental footprint through energy emissions, waste, and their use of materials?

Consider where hand woven rugs are made. Many countries' child protection and labor laws are different than those of the U.S. Look for a guarantee or certification that ensures no one was harmed in the manufacturing process.

How will you install it?
Tacking down carpet is best, but if you decide to glue, look for a water-based adhesive with low VOC content. To make your flooring last even longer, install a tiled system to facilitate easy replacement of troubled sections.

Is it recyclable?
There are many companies that are willing to take your old carpeting off your hands to reuse it. If you think you can salvage it yourself, consider dying it a new color and revitalize the whole room!

Don't wait for the grass to be greener on the other side – install eco-friendly flooring in your own home, and let the green surround you.

Since 2000, Chris Long has been a store associate at a Home Depot in the Chicago suburbs. Chris contributes DIY flooring advice on hardwood and tile flooring for the Home Depot website. He also provides tips on carpeting, area rugs and other floor covering options for the website.

Category:

Buidling Envelope and Materials

Flooring

First LED bulb revolution - sub $10 bulbs

ckmapawatt — Fri, 11 Oct 2013 12:49:15 +0000

In March we wrote about Cree breaking the $10 barrier in an A19 LED bulb. Now several other manufacturers are following suite.

Green Tech Media has a great article on the new LED bulbs from Philips, GE and Wal-Mart that are also right around the $10 mark. From the article:

"The incumbents were watching and have answered. Last month, Philips partnered with Home Depot and utilities to bring the price of its 60-watt LED equivalent to $9.97 after utility rebate. For regions without a utility rebate available, its 10.5-watt A19 will be offered for $10.97.

Philips also started offering instant utility rebates for its LED bulbs at many Staples stores last month. Ikea was early onto the LED bandwagon. The Swedish retailer said last year it would only sell LEDs after 2016.

On Wednesday, the world’s largest retailer also got into the game. Wal-Mart is selling its line of Great Value LEDs for less than $10. Wal-Mart rolled back prices all the way down to $8.88 for a 60-watt-equivalent, soft-white bulb that is not dimmable. Wal-Mart will also offer a new dimmable 60-watt equivalent by GE for $11. GE is also selling its Reveal LED for about $20 at other retailers.

“GE and Wal-Mart have worked in close concert for more than a decade to pioneer new applications for commercial LEDs,” John Strainic, GE Consumer Lighting General Manager, said in a statement. “We’ve taken the good collaboration we’ve made with Wal-Mart to increase the energy efficiency of their facilities, and are beginning to make the same inroads in the consumer lighting aisle.”

Seeking Alpha also has a pretty good article of the Cree bulb vs. Wal Mart bulb.

Aside from price, make sure you compare color temperature, wattage, lumen output and if the bulb is dimmable or not.

Still waiting to upgrade from your incandescents to LED? Why? If you keep your lights on 3 hours/day and you pay around $.10/kWh, then one of these new LED bulbs will cost you around $18 (initial bulb cost and electricity) over 5 years. An incandescent is going to cost you $34.21 over that same time period!!!

Play around with our calculator below to see the economics on different options.

Tags:

LED bulb comparison

Category:

Lighting

LED

Wipe out Waste in the Bathroom

ckmapawatt — Sun, 29 Sep 2013 18:37:06 +0000

The following guest post is written by Chris Long from Home Depot.

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When you think about the most effective places in a home to remove waste, kitchens and bathrooms probably top your list. After all, kitchens with their trash cans and garbage disposals make getting rid of waste a cinch and toilets, well, without toilets in our bathrooms we'd have to venture outside on a daily basis!

But what about another type of waste that occurs in the bathroom that we want to eliminate? In other words, even though the bathroom is effective at removing waste, is it as efficient as it should be?

Of course, the other kind of "waste" we want to wipe out in the bathroom refers to wasted energy! From water to electricity, the bathroom is one of the main sources of wasted energy in the home and the biggest culprits are those inefficient fixtures including everything from shower heads to light sockets.

Fortunately, there are simple ways to fight to keep more of these precious resources from getting flushed down the toilet; which also keeps more of our hard-earned money from washing down the drain. Here are some eco-friendlier updates for those wasteful plumbing fixtures in the bathroom.

Toilets

Although most people assume the shower is the worst water waster in the home, bathtubs get a bum rap (relatively speaking) because the biggest bad boy is actually the toilet.

Indeed, 30% or more of your household water usage is directly attributable to your toilet. But with toilets that are backed by the EPA's WaterSense seal of approval, you can cut that consumption by 20%.

While we're on the subject of WaterSense, in order for the EPA to certify a product as genuinely water efficient, the product:

Must be at least 20% more water efficient than other products in the category (faucets, toilets, etc.).
Must provide measurable results that help to realize water savings on a national level.
Must achieve water efficiency through multiple technology options.
Receives independent testing and third-party verification and certification that all guidelines have been followed and criteria met.

Basically, the WaterSense label is to fixtures that are more water efficient what the Energy Star label is to more energy-efficient appliances. All in all, looking for those labels on any products you purchase can help ensure you go far in your greener endeavors!

Due to the often cost prohibitive replacement expense, a simple DIY option for reducing your toilet's water waste is outfitting your existing toilet with a dual flush option.

BlueSource HydroRight Dual-Flush Converter
This dual flush converter provides the ease and efficiency of a two-flush option toilet with your current unit without requiring you to remove the tank or utilize complicated plumbing supplies. Plus, you still get the same amount of power for your full-flush option but now you have the added bonus of a low-flow flush.

*Tip: While converter kits typically fit most modern toilets, if you have an exceptionally old model (pre-1994), make sure the kit you purchase will satisfy the specifications of your toilet.

Faucets

For a faucet to receive the "all clear" in the EPA's water efficiency department, it must allow no more than 1.5 gallons of water per minute (GPM).

When you consider that swapping out your old faucets and aerators with WaterSense models can save an average family of four 700 gallons of water per year, or the amount of water you could use in 40 showers, without doing anything extra to save water, you start to see just how much Sense the switch makes!

*Tip: Simply turning off the faucet while you brush your teeth can save an average of 8 gallons of water per day - that's nearly 3,000 gallons annually per person!

NEOPERL 1.0 GPM Super-Saving Faucet Aerator Insert
A money and water saving idea - instead of replacing all of your faucets - is to simply replace your current faucet aerators with WaterSense attachments. This step alone can save up to 55% water when compared to the standard 2.2 GPM aerators (on non-water-efficient faucet fixtures).

*Tip: Be sure to take your existing aerator with you when you go to purchase a replacement. Simply unscrew the tip of your faucet and remove the tiny aerator insert inside.

Shower Heads

One of the best aspects of swapping out your 2.5 GPM or more water hogging shower head with a newer low-flow model that uses 2.0 GPM or less (many coming in around 1.5 GPM!) is the cross-resource savings that you receive: not only do you curb your water usage, but you can also cut costs in the energy department by having less water to heat! Win-win.

*Tip: While you wait for your shower water to heat up, catch all that cool water that would otherwise run down the drain. Keep a clean bucket next to your bathtub and use it every time you take a shower. From there, use it for everything from watering your garden to refilling Fido's water bowl or even helping a load of laundry use less water!

Light Fixtures

Don't forget about the other fixtures in your bathroom - your light fixtures.

By replacing your current incandescent bulbs with new LED bulbs, like this one from Cree, you can conserve up to 84% more energy.

Plus, these don't heat up like old school light bulbs which make them ideal for a bathroom - no more melting makeup!

What other DIY water and energy-efficient measures or updates have you undertaken in the bathroom?

Chris Long is a Home Depot store associate in the Chicago suburbs. He writes on plumbing and bathroom DIY for the Home Depot website. Chris' advice focuses on everything from toilet repair to plumbing fixtures.

Category:

Energy

Heat pump vs. Natural Gas Furnace

ckmapawatt — Fri, 23 Aug 2013 12:34:16 +0000

There are 2 main types of heat pumps: Air source and Ground source. This article mainly compares and air source heat pump to a natural gas furnace. We like the EnergySavers.Gov page on how a Heat pump works. The biggest drawback to heat pumps is that in cold climate they probably will need supplemental heat, because they can't pull any heat from the outside air if it gets too cold.

In our post "Heat Pump - will an air-source work for you" we stated:

The state of California has a good description of air conditioners and heat pumps on their Energy Quest site (even though it looks like it is made for kids it has some great explanations):

"A heat pump is an air conditioner that contains a valve that lets it switch between "air conditioner" and "heater." When the valve is switched one way, the heat pump acts like an air conditioner, and when it is switched the other way it reverses the flow of the liquid inside the heat pump and acts like a heater."

The DOE Energy Savers Heat Pump guide has a great introduction to what a Heat Pump is and where it works:

"For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to move heat from a cool space into a warm, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house; during the cooling season, heat pumps move heat from your cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide up to 4 times the amount of energy they consume."

My biggest question with this opening paragraph is what defines a moderate climate? While this isn't defined by Energy Savers in their heat pump section, they do touch on it in the Heating with Electrical Resistance section:

"If electricity is the only choice, heat pumps are preferable in most climates, as they easily cut electricity use by 50% when compared with electric resistance heating. The exception is in dry climates with either hot or mixed (hot and cold) temperatures (these climates are found in the non-coastal part of California; the southern tip of Nevada; the southwest corner of Utah; southern and western Arizona; southern and eastern New Mexico; the southeast corner of Colorado; and western Texas). For these dry climates, there are so few heating days that the high cost of heating is not economically significant."

But I think Energy Savers was a bit conservative in listing areas where heat pumps don't work so well. From their air-source heat pump page they state:

"When outdoor temperatures fall below 40°F, a less-efficient panel of electric resistance coils, similar to those in your toaster, kicks in to provide indoor heating. This is why air-source heat pumps aren't always very efficient for heating in areas with cold winters. Some units now have gas-fired backup furnaces instead of electric resistance coils, allowing them to operate more efficiently"

When discussing which technology is best for heating our homes in his latest post on The Shocking Truth About Heat Pumps, home efficiency expert Allison Bailes states:

"The truth is that anyone who says never or always is usually wrong, especially when it comes to which products, materials, or technologies to use in your home. In the case of gas heating versus heat pumps, here are some of the issues you need to consider:

Climate zone
Electricity vs. gas rates and service charges
Where your electricity comes from
Building enclosure
Modern equipment"

And closes with:

"Heat pumps today aren't the same as the early models from the 1970s and '80s. They're more efficient. They've got the supplemental heat thing figured out. And they come in a wide variety of efficiency, capacity, and technology, from the standard models to mini-splits to ground-source heat pumps.

Of course, furnaces (and boilers) have come along, too. We now have high-efficiency, sealed combustion furnaces that can distribute the heat through either forced air or hydronics. You can get a modulating condensing (mod-con) furnace that can adjust the capacity closer to the needs of the house.

Overall, it's easier and less expensive to get a heat pump small enough to match the loads of a high performance home than it is to get an appropriately sized furnace. Mini-splits are great for this and allow for better zoning, too.

In the end, you shouldn't go with a furnace just because an expert said all heat pumps are unacceptable. You've got to look at the issues I outlined above. Consider what your priorities are. Low energy bills? Environmentally friendly energy sources? Uniform heating with lower temperatures or short blasts of higher temperatures?

The shocking truth about heat pumps is that they might well be a great fit for your home. Or they might not. It depends."

Residential Solar PV case studies

ckmapawatt — Sat, 17 Aug 2013 18:41:41 +0000

The internet makes it very easy to google a phrase online and find a bunch of info on that topic. But to be honest, most of the time that info is crap. It's sites that are trying to sell you something or that have gamed the google rankings to push themselves higher in the page rank. If you googled "residential solar pv case studies", chances are you may find some good info. But most of it would be from solar installers trying to sell you a system, which isn't a bad thing at all, but what you really need to hear from is the homeowners. Luckily, there is a great website that features cased studies from real people who have decided to install solar on their homes.

EnergySage.com has a great section of residential solar pv case studies. Not all of them are homes, but you still get to see the financial impacts of installing solar on a wide range of properties. Here are the financial details of this 12kW solar PV tracker system installed in Princeton, MA.

Financial Details

Gross Cost of System:: $84,000

Value of Tax Credits:: $25,000

Net Cost of System:: $60,000

Annual Savings:: $5,000
Own or Lease:: Purchase (Own)

Everyone knows solar is expensive, but not everyone realizes how solar can act as an investment. By reading through some of these case studies, it helps other homeowners understand how the financing of solar can play out on their home. Of course, read our Residential Solar PV installation guide first, so you know the basics and how your geography is going to impact that investment (amount of power produced, utility rebates, etc).

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BMW i3 Electric Hybrid better than Chevy Volt?

ckmapawatt — Fri, 16 Aug 2013 19:11:41 +0000

It's not as beautiful as the Tesla Model S, but it also doesn't need a Supercharger network to prevent Range Anxiety. The new BMW i3 is an electric vehicle with a gasoline "range extender" option.

From the BMW USA i3 page:

"The BMW i3 with Range Extender takes you further, allowing you to breathe a little easier on those longer road trips. This model, with a two-cylinder combustion engine, generates electricity that maintains the charge of the lithium-ion battery at a constant level as soon as it dips below a certain value.

The BMW i3 with Range Extender doubles your electric driving range to eliminate range concerns."

Further explanation from Green Car Reports:

"The range-extended option marks out the i3 as a competitor for Chevrolet's Volt, but unlike GM's product, the i3 'REx' will require you to make a few compromises on range and performance.

That's because the 650cc maxi scooter-sourced, twin-cylinder gasoline range extender (quite a mouthful, so let's hope you don't have to explain it to people too often) is really a last resort, rather than a genuine aid to longer-distance driving.

BMW seems to have admitted as much by allowing drivers a free loaner whenever they need to tackle a longer distance, but the clues are in the i3 range-extended model's specification too."

Would you get this, or just wait and see if BMW will release the i8!

In a later post, we'll look at how the i3 compares to the Volt from a range and cost perspective.