Wattvision's Blog

Sun and Wind Powered Clothes Dryer v. Electric Dryer

This is the fifth in a series of guest posts by Ted Borer, PE, the energy plant manager for Princeton University. He is actively involved in campus and community energy efficiency and carbon emissions reduction efforts. He has over 25 years of experience in the energy industry, is a registered professional engineer, and holds both undergraduate and graduate degrees in Mechanical Engineering as well as the CEM, CEP, and LEED^AP Certifications. He has published numerous magazine articles, technical papers, and a book chapter on topics relating to energy and cogeneration. 

The Wattvision offers us a means to study our electric use in highly granular detail. By looking closely at the data and considering what is happening in the house, we can determine both the magnitude and duration of electric use for a specific activity. Then we can easily calculate the cost and decide whether that cost is good value.

What follows is a close technical analysis of my energy use.  Wattvision may automate these sorts of analyses, but until that time nothing beats looking at the data.

For example, the graph below shows a recent day where we ran the clothes dryer starting at about 12:15 PM.

Let’s look at that time period in detail by selecting a range between 12:00 and 2:00 PM.

Looking at the detail above, or referring to a .csv (comma separated values) file downloaded from wattvision, it’s easy to see that the dryer ran from 12:13 PM until 1:20 PM. Before it began, there was a base-load electric use of 1700 watts in the house. We can imagine the drum motor running continuously and a resistance heating coil turning on and off based on a temperature and humidity signal. The drum motor may only use a hundred watts or so, but the resistance heating coil looks it draws about 5000 Watts when it’s on! Since it cycles on and off, the average household demand during the operating period is about 5500 Watts. 

With that information we can determine the energy consumption and cost of drying a load of clothes:

5500 Watts while the dryer operates

-1700 Watts base-load activity

3800 Watts, average clothes dryer use rate 

From 12:13 until 1:20 is 67 minutes or 1.117 hours

(3800 watts) x (1.117 hours) / (1000 watts per kilowatt) = 4.2446 kilowatt-hours

If our power costs $0.20/kilowatt-hour, then drying that load of clothes cost:

$.20 x 4.2446 = $0.85 

If we dry one load of clothes per day for a year, then our annual clothes drying expense is:

$0.85 x 365 days = $310 

…and we’ve used: 

4.2446 kilowatt-hours x 365 days = 1549 kilowatt-hours

Now we can consider whether using an electric dryer is worth the convenience, cost, and environmental impact or if we’d be willing to save $310 per year and reduce our carbon footprint by hanging our clothes on a line outdoors. Even if we paid $150 for a fancy “sun and wind powered” outdoor clothes dryer, it would have less than a six month payback! So we can easily justify it even if it’s only used in the summer. 

Anticipate Collateral Benefits

This is the fourth in a series of guest posts by Ted Borer, PE, the energy plant manager for Princeton University. He is actively involved in campus and community energy efficiency and carbon emissions reduction efforts. He has over 25 years of experience in the energy industry, is a registered professional engineer, and holds both undergraduate and graduate degrees in Mechanical Engineering as well as the CEM, CEP, and LEED^AP Certifications. He has published numerous magazine articles, technical papers, and a book chapter on topics relating to energy and cogeneration. 

We are all familiar with the concept of collateral damage, i.e., when one system fails, something downstream is also damaged. When a nail punctures your tire, the tire goes flat, but you’re also forced to drive slowly and are late to get somewhere, then if you drive on the rim to get home, both tire and rim need repairs.

I’d like to suggest that the reverse is also true, and our efforts to save energy will often yield delightful and unanticipated “collateral benefits.”  Here are a few examples:

(download)

Click here to download:

anticipate-collateral-benefits-mCsJdlEmIcxAtraJJGIe.zip (136 KB)

We replaced an old oil-fired furnace with a new electric heat pump. The upgrade was justified on life-cycle savings alone. I.e., the cost of new equipment (less rebates and incentives) plus the cost of several years of operation was actually less than the cost of operating the old, dirty, inefficient equipment for several more years. Saving money was just the anticipated benefit. We also knew that by using a highly-efficient heat pump instead of burning home heating oil we would substantially reduce our family carbon footprint. But what we hadn’t anticipated were a few other nice benefits:

• We eliminated the liability of having 270 gallons of diesel fuel stored in our basement. 
• By replacing a combustion process with electric equipment we were able to move the air handler from the middle to the corner of the basement, allowing more recreational space.
• By eliminating the oil tank, we freed-up even more recreational space.
• We eliminated fuel oil deliveries.
• We moved ourselves farther from foreign fuel.

In another project, we did air sealing and added extra insulation in the house. We measured the “infiltration” (air leaks through all the tiny cracks and gaps in the house) before and after this work and anticipated about 19% reduction in energy use. In fact, that turned out to be a very accurate prediction of our energy savings. What we hadn’t anticipated was that the house would be quieter and more comfortable. With less leakage, the heating and cooling equipment didn’t have to run as often. With less leakage, the house was less drafty and more comfortable.  With less warm air exhausted through leaks, less cool air was pulled in through the basement. This resulted in such a dramatic decrease in measured radon levels that we were able to shut off the 100 watt radon exhaust fan – further reducing our energy use continuously all year!  (100 watts) x ($0.18/kilowatt-hour) x (1 kilowatt-hour/1000 watt-hours) x (8760 hours per year) = $157.68 savings per year! A nice added benefit!

Just a slight caution: think before you act. It is possible to make energy-saving changes that aren’t entirely satisfactory. For instance, do consider all the qualities you’d like in a new light bulb. That energy efficient LED light may be ideal. But think first about whether it’s got the right shape for your fixture and the right light color, and can dim if you want it to. Does it make noise? Will you use it enough hours to justify the cost? 

But go ahead and dive in! Start making thoughtful energy-saving changes. Think. Plan. Act. Then, expect to be delighted with unanticipated collateral benefits from your work!

Wattvision Responds to PowerMeter's Shutdown

We at Wattvision continue to work hard and our goal remains the same -- being the best end-to-end, hardware and software solution for consumers and businesses seeking to save money on energy.  So the big question is, what do Wattvision users "lose" when Google PowerMeter shuts down? Fortunately, nothing.  To simplify this post, we've broken it down by audience:

For Current Wattvision Users:

In a few clicks, you can stop sending your wattvision data to PowerMeter anytime before the official shutdown date, from your user account page. We will start doing this automatically as the date approaches.

For Users Interested in Energy Monitoring:

Since we've been shipping hardware and software since 2009 -- we already have a site where users can view, analyze, and compare data with other users. That's our site, wattvision.com, viewable on the web or on your mobile device.

Wattvision also has a few extra features like email alerts, charts updated every 10 seconds, and a live API, for example.  Many users have commented that they like our site better than PowerMeter's. Great! But the PowerMeter interface had a few neat features like comparisons with previous data. They're on our to-do list, and we'll continue to add features based on your feedback.

For Developers of Hardware and Software in the Energy Monitoring Space:

Like PowerMeter, we don't want to lock up your data.  You can download your data to your computer for analysis, or use our beta developer API for upload from your sensors or download to your apps.  We also hope other hardware and software developers will recognize wattvision as a reliable platform -- a platform that enables them to build products that help users manage energy consumption and save money on energy.

We first heard of Google PowerMeter about one month into our YCombinator funding round in January 2009.  You can still read their original announcement post.  Needless to say, we were scared.  A few of our closest advisors and friends said, "Google's in your space, you might as well give up now.  But hey, at least it validates your idea."  Thanks to our YCombinator connections we did get to meet with the PowerMeter team and work on compatibility betwen our products. It was a pleasure to work with them and it's a shame to see the product go.

The attention that the Google brand brought to our space was quite a boon for us, as well.  Without Google, we'll continue to work hard, make our customers happy, and generate our own excitement. On that note, just for this weekend we've announced a coupon (ends Monday 12:01a) $50 off, coupon code "byepowermeter".

New Feature: Monthly View

Hi, I'm Diego, a Software Engineer at Wattvision.

We have recently added a highly requested feature to the site, a monthly view of your historical data. To help you get more out of Wattvision we're actively working on a series of features that our users will appreciate. Here's how to get to the monthly view:

Simply go to your house's "My House" page, and then click on the "History" tab. You'll see two options, one for a daily look at data, the other for a month long view.

What can you do with it? Here are some ideas:

• Can you spot seasonal trends? Has your A/C started running recently? Is it inreasing your monthly bill substantially?
• Conversely, do any consecutive months, or months of the same season, differ substantially? Why?
• Did you change appliances recently? Can you find the date you changed them? Are you saving money?

We are working hard to give you easier access to your information, and this is a small step in that direction. We love ideas, do keep sending them our way. If there's any feature or improvement you'd like to see please let us know.

-Diego

(can you tell when the A/C kicked in for the summer?)

Wattvision: What to do with all this cool data?

This is the third in a series of guest posts by Ted Borer, PE, the energy plant manager for Princeton University. He is actively involved in campus and community energy efficiency and carbon emissions reduction efforts. He has over 25 years of experience in the energy industry, is a registered professional engineer, and holds both undergraduate and graduate degrees in Mechanical Engineering as well as the CEM, CEP, and LEED^AP Certifications. He has published numerous magazine articles, technical papers, and a book chapter on topics relating to energy and cogeneration. 

The Wattvision system offers a highly-detailed look at our energy use. It can measure the magnitude and duration of events that last for less than a minute and demand only a few watts, yet the data can be collected over a period of days, months, or even years. This level of detail offers us insight that we could never get by reviewing a monthly electric bill, or even by seeing an hourly total of power use. By carefully observing the patterns and durations of events in our energy use, and superimposing what we know about what is happening at the time, we can determine which activities use the most and least energy and which we may want to modify.  

Let’s break this down into manageable steps.

First it is helpful to develop a simple inventory of the things that use energy around the house. This may be informative when interpreting the Wattvision graphs and data.

Click here to download:

wattvision_energy_inventory.pdf (55 KB)

(download)

Click here to download:

wattvision_energy_inventory.pdf (55 KB)

We don’t need to be rigorously thorough or gather complete information about every light bulb. We just need to list the energy consumers that either use a lot of energy, or use energy for a long time. If you need ideas about what to look for around your home, the US Department of Energy offers a list of typical appliances and the energy they consume. This gives us a sense of what are large and small energy consumers, but it is important to check your specific equipment since there are great variations in efficiency and personal use.

Once we know what consumes energy, we’ll make a log of energy events for a while.

Click here to download:

wattvision_event_log.pdf (62 KB)

(download)

Click here to download:

wattvision_event_log.pdf (62 KB)

Then, we can combine this information with the Wattvision graphs and data to determine which activities used an important amount of energy, and which activities used less. The patterns, magnitude, and durations of events we see in the graphs will give us important clues as to what is happening. 

After making the log entries shown above, this graph was created by downloading that morning’s data from the Wattvision history page, opening it with an Excel spreadsheet, and adding notes.

Click here to download:

wattvision_saturday_allday.pdf (25 KB)

(download)

Click here to download:

wattvision_saturday_allday.pdf (25 KB)

Click here to download:

wattvision_saturday_morning.pdf (196 KB)

(download)

Click here to download:

wattvision_saturday_morning.pdf (196 KB)

Now we can begin to make a few observations about this snapshot of our energy use:

1. The biggest energy user is a steady demand of over 3500 watts. It was 20°F outdoors that morning. No doubt  most of this demand is from our electric heat pump that provides a large portion of our heating energy. If this ran at the same rate all day, it would cost: (3500 watts) x (24 hours) x ($0.19/kilowatt-hour) = $15.96/day!
2. There are random periodic spikes of over 500 watts. They are too many watts and too brief to be lighting. They may be associated with the well pump coming on to restore water pressure after toilet and sink use.
3. The coffee maker uses about 1000 watts for about five minutes. What does that cost? ($0.19/kilowatt-hour) x (5 minutes) x (1 hour/60 minutes) =  $0.0158, i.e., less than two cents. So the coffee and cream cost more than the electricity to make a latte’.
4. Cooking on the stove top or in the toaster oven both appear to use about 1900 watts apiece for several minutes.
5. There are two similar-looking steep downward spikes in energy use of over 1000 watts for about 5 minutes each. They are about 90 minutes apart. After the drop, energy demand increases again gradually over several minutes, not all at once. No specific energy event was noted in the log, so these may be associated with something that runs automatically. They are large enough that they probably relate to the heat pump. They may be associated with the heat pump defrost cycle. This is worth further investigation. Two sources of information would be the equipment nameplate and the owner’s manual.

We’ve made guesses about some of the events in the graph above. But repeated log entries and graph observations will allow us to confirm or correct these. The important thing is to begin by making observations to sort out what is happening. Then we can see what may be worth adjusting and what may not be worth the effort, inconvenience, or expense. What do we have control over? What are we interested in changing? Appliances that use a lot of power for a long time will have the biggest impact. If we have limited time and resources, the graph above suggests we’re better off looking for ways to reduce energy used by our heat-pump than by getting a more efficient toaster, stove, or coffee maker.

Wattvision looks great on iPhone and Android

If you have an iPhone or Android phone, wattvision looks great as a web app. Just pop open your browser and visit http://www.wattvision.com.  You'll automatically get redirected to our mobile site, which is useful for walking around your house, turning things on and off, and observing the effects on your whole home's energy use. You can add the page to your home screen, as well.

(download)

Click here to download:

wattvision-looks-great-on-iphone-and-android-kJHwcDyDvmBqBJlbdjFD.zip (378 KB)

Does a Wireless-B device slow down a Wireless-G network?

The wattvision gateway, pictured below, is an 802.11B device.  It connects to your home's network and uploads the energy use data it gathers from the wattvision sensor attached to your meter.

Some of our customers have qualms about the speed of our gateway.  Won't a wireless-B device on my G or N wireless network slow down traffic for everyone? The short answer: no, it won't.

This paper, published by Microchip last year, is a study of network performance in a mixed networks and reaches this conclusion.  Can you cite a study that proves otherwise? Let us know!

Click here to download:

microchip-report.pdf (198 KB)

(download)

Click here to download:

microchip-report.pdf (198 KB)

Quotes

We were just looking over some quotes from early press about wattvision. Here are three from EnergyCircle, TechCrunch, and Scott Adam's Blog (yes, the Dilbert Creator).  We're really honored to get feedback like this!  We were also excited by the reviews on the energy circle product page.  We strive for 5 star reviews and happy customers!

Wattvision: The Initial Setup Experience

This is the second in a series of guest posts by Ted Borer, PE, the energy plant manager for Princeton University. He is actively involved in campus and community energy efficiency and carbon emissions reduction efforts. He has over 25 years of experience in the energy industry, is a registered professional engineer, and holds both undergraduate and graduate degrees in Mechanical Engineering as well as the CEM, CEP, and LEED^AP Certifications. He has published numerous magazine articles, technical papers, and a book chapter on topics relating to energy and cogeneration. 

My initial experience with the Wattvision system has been really enjoyable. This device has a very simple web order form. I opted to have it “pre-programmed” by entering a few pieces of information from the nameplate of our wireless router into the order form. It arrived a couple days after the order was placed with no expedited shipping costs or extra fees.

I could have had my ten year old hook it up – if he was tall enough to reach the electric meter. Here are the steps it took:

• Strap the sensor onto our electric meter with one flat-blade screwdriver.
• Adjust the location of the sensor on the meter with a thumb screw and verify the LEDs are flashing in synch with the dial rotation (no tools)
• Plug the sensor wire into the transmitter
• Plug in the power supply to a wall outlet
• Plug the power supply into the transmitter
• Watch as the LEDs light up and indicate power, connection to the router, and connection to the Wattvision servers.
• It worked. There was no fussing, programming, or troubleshooting at all!
• Note: The wireless router needs to be on at all times, but the computer and other peripherals can be shut down completely.
• Found www.wattvision.com on my Android phone and can now see our house power use from anywhere!

The whole “installation” took less than fifteen minutes between arrival and full functionality – including playing with the sensor on the desk just for fun to see it work (sensing dark and light) before installation on the meter. Note: The Wattvision system did not come with an instruction manual or installation CD. Amazingly, it doesn’t need one! It is truly a “plug & play” device.

Let’s step back for a moment. What do I want to do with this thing? What am I expecting of it?

Ideally, I’m hoping to learn and answer questions:

1. How much electric power are we using at our house?
2. Which things do we operate that demand all that power?
3. What costs a lot to operate?
4. What devices or behaviors could we modify to reduce our power use?
5. What changes would be cost-effective without causing us great inconvenience? I’m sure there are things that we could do that we wouldn’t want to or that would be too expensive for us. We have no interest in sitting at home in a cold, dark, silent house. We just want to learn where we are wasting energy and find ways to reduce that.
6. When we make changes, I want to verify that the changes had the anticipated result in power and money savings.
7. I expect to have some fun playing with this new gadget.

My first insight was pretty basic: WOW! Are we really using 4000 watts this evening?!! Steadily? That can’t be right. I thought we turned off most of the stuff in rooms where no one is. Where’s it all going? For context, it’s January, the coldest month of the year. We have an electric heat pump providing about half the heat for our house and an extremely efficient fireplace providing the rest. But we also have a fairly tight house and think we’re pretty good about energy use.

After letting the Wattvision run a while and switching on and off some lights to see that it responded accurately, I looked at the “current consumption rate” graph for the previous hour. This is a green line graph with time in a blue field on the x-axis. I noted brief upward spikes about every half hour. What’s that? Perhaps it’s the well pump coming on to maintain water pressure in the system?

One thing that appears critical to get the most out of this tool is to observe the data and then super-impose whatever I know about what is happening at the time.

Check the “history” graph below. There is a blue line showing consumption rate in watts every fifteen seconds. It’s easy to right-click on the blue time axis and to use the mouse wheel to expand and contract the time range.

It looks like we were only using about 500 watts between midnight and 2:30 am. Then power use jumped up. Here’s my guess at what happened: The bread machine was set on a timer to have bread ready for us at 6:30 AM. It takes about four hours to cook. So it should have started automatically at 2:30. The only problem is that the bread was finished at 6:30 and power use continued at a relatively steady 4kW even after that. Was it also the heat pump that increased power demand?

So what’s happening in the graph above? It looks like the electric dryer ran from mid-morning until 11:47 AM, then shut off. The dryer heating element must use about 5500 watts. I can verify that by checking the nameplate or owner’s manual. Let’s do some easy math. Say the dryer averages 5kW for an hour of operation. Then one clothes-drying cycle costs:

(5 kilowatts)  x  (one hour)  x   ($0.19/kilowatt-hour)  =  $0.95 to dry a load of clothes.

That might be off a little, but it seems about right.

The heat pump must be off or on “low” during the end of this time period. 890 watts of stuff is running. The small spike about 12:18 AM was probably the microwave heating lunch.

This is pretty cool! More to come! Buy a wattvision sensor for your house at wattvision.com.

Why we should've named our company "A1 Wattvision" :)

Many users discover Wattvision because of our compatibility with Google PowerMeter.  Set up your Wattvision system, and with a few clicks on your account page, you can opt-in to send your data to Google PowerMeter -- Google's foray into the energy monitoring space.

We're honored to work with Google, and our beta users have enjoyed Google PowerMeter support since February of last year. We just recently exited beta and got listed on PowerMeter's website.  Here's a screenshot:

We can only guess at how many more customers would come our way if our company name were "A1 Wattvision" instead of "Wattvision."  Though a "W" as our first letter puts us as a slight disadvantage with respect to the quick-clicking web-user, we hope the quality, ease of use, and care we put in to our product design will help Wattvision bubble to the top of the list in people's minds. ;) Happy Friday!