Wiring a Generator to Your House

We're going on day 5 without utility power at my house in Pennington, New Jersey.  Thanks to Wattvision, we know our home's exact load profile, so we were able to match our generator to our needs, saving tens-of-thousands of dollars in the process.  I'd like to share how we did it, so you can do it, too.  Let's first take a look at the typical load presented by our house on a given day, as recorded by our Wattvision system last Thursday, October 25, 2012, in the pre-Sandy world:

So looking at the graph, with time on the X-axis and watts on the Y-axis, you'll notice that we never use more than 5000 watts, and only come close to that for a very short period in the day.  Zooming in, we were close to 5000 watts for just a minute or so that night:

Just for fun, try to guess the average rate of consumption for the whole day, in watts.  Go on, give it a guess.  

It turns out that, on an average day, we use an average of about ~660 watts throughout the day.  What that means is, if we had a power source that generated just 660 watts, coupled with a 100% efficient battery that could accept and return power perfectly, we could power our whole house on just a 660 watt constant power supply.  But that's not possible in this universe, so let's get a generator...

Choosing a Generator

Looking at our data on the typical day above and other days, we know that we'll never need more than 5 kilowatts for typical use in our home at this time of year.

Now, the wiring in our house can support 400 amps of current at 120 volts, so that's a cool 48,000 watts.  Most typical American homes support up to 24,000 watts.  So you can understand why a generator salesperson might want to sell you a system that can produce 20 kilowatts or more. "Because you never know!"  But in our case, we have the data and the confidence that we won't need that.

During Hurricane Irene last year, we spent several days without power.  On one of the last days, we purchased our 5.5kw gasonline-powered generator.  This is a standard generator that you might find at your typical hardware store, but it also has a 120v/240v NEMA L15-30 outlet.  We fired it up, and wired it directly to our home's well-water pump.  I still remember the excitement we felt when we restored running water to our house.  And then, while we were celebrating, the power came back.  Thankfully we saved the generator, and it's come in handy during Hurricane Sandy.

Wiring it up...

So you have a generator -- how do you wire it to your home's breaker box, ensuring your whole house is back online?

The first thing you'll need to verify is that your generator has a NEMA 240v/120v L15-30 or similar outlet.  This is a special round, typically 4-prong plug that has neutral, ground, and two "hot" 120v lines.

The next thing you'll need to do is contact an electrician, to set up either a generator interlock, or a separate generator-powered breaker panel.  The emergency circuits breaker box is a common route, but isn't ideal -- you have to select the subset of circuits in your house you want powered by your generator.

In our case, we want to use everything in our house, so we opted for a generator interlock kit.  The interlock is essentially a switch that allows you to either power your house from the utility or from your generator.  When the power goes out and you know it'll be out for some time, you go to your breaker panel, flip a switch, plug in your generator, and fire it up.

If you try to wire your generator to your breaker box as a DIY project, you probably will not be in compliance with local electrical codes.  Also know that it's extremely dangerous.  For example, if your ground wiring is not done properly, you may inadvertently put 200+ volts on 120 volt lines, immediately frying bulbs and electronics connected to those lines, and potentially starting fires.  Don't do it.

So how much does it cost to run?

When powered by the utility, we use about 15 kWh / day at the current rate.  At 17 cents per kWh, we have some of the most expensive electricity in America, but it's still only about $3/day at the moment, thanks to our Fall climate here in NJ, and our optimization with Wattvision.

The generator uses about 8 gallons of fuel if we were to run it constantly for 24 hours.  Assuming you can get a gallon of gas for about $3.50, that's about $28/day.

But, we can regulate our consumption -- we turn the generator off at night, for example.  By optimizing our use, we've been running the generator for less than half the day.  So about an extra $10/day over what we were paying normally.  A decent rate if we're talking about only a few days without power every year.

Of course, that's putting aside the environmental cost to run our generator. But that's a blog post on its own. :)

What about Batteries?

The energy required to run our home for a typical day last week was about 15 kilowatt-hours.  So how many AA batteries is that?

A single high-end rechargable AA battery is rated at 1.2v at 2 Ah. So that's 2.4 Wh.  So to run my house for a day, we'll require at least 6,250 AA batteries. Putting aside the cost of the management electronics and all the wiring and little boxes we'll need to buy for these batteries, that will cost > $15,000.  Ouch. (You can buy a pack of 8 batteries for about $20 on Amazon).

How about deep-cycle 12 volt batteries?  You can buy a single battery for ~$130. This battery produces 55Ah and contains 660 watthours of energy. you'll need about 22 of these batteries, and it will cost about $3000 -- a little more reasonable.

Final word...

Since we have electrically-pumped well-water here in NJ and the natural gas line to our house was not disrupted, the 5.5kw generator wired to our breaker box restored our house to life as normal.  Granted, we can't think about running one of our 3 A/C units, which easily pull 5kw each, but in a pinch, the generator is just what we need.

Hopefully our power will be restored soon -- we're busy at work producing Wattvision 2, so we can ship it out to kickstarter backers in January. :)

Analyzing Computing Power with Wattvision

Some people leave their computers on 24/7.  Others turn them off at night and boot them back up in the morning.  Have you ever wondered what's more power efficient?  One Wattvisionary with a few computers on his hands decided to find out.

Jon R. ran a large, high-end PC day and night in his household as well as a smaller office laptop that he only used rarely.  By using Wattvision, he discovered that his PC was costing $32 per month and his laptop was adding on an extra $7 per month.  By shutting down his laptop when not being used and putting his PC on a sleep schedule, he was able to save a significant chunk of money on his monthly energy bill.  

Have similar questions about your home's energy use patterns?  Don't be in the dark forever; get Wattvision and answer your questions with accurate numbers to help you make the most cost-effective choices for your household.  Every saving adds up, and even one change added up over months can make a huge difference.  

Also, don't forget to check out our Kickstarter here.  Every backer counts!

Wattvision's Kickstarter Now Halfway to its Goal

By now, you've probably heard about our Kickstarter campaign, which can be found here: http://www.kickstarter.com/projects/wattvision/wattvision-the-smart-energy-sensor?ref=live

In just the first 5 days, we've reached half of our campaign goal of $50,000 thanks to support from Wattvisionaries around the world, including Treehugger and lots of re-tweets!  However, we still have a long way to go to get to our goal and so we still need your help.  Get the word out to everyone you know about how Wattvision is revolutionizing the way we look at home energy consumption and share our Kickstarter link anywhere you can... we can't do it without you!

Energy Monitoring is Vital for Energy Efficiency

Amidst calls for energy efficiency and going green, it's easy to be overwhelmed with where to start and what to change in your life or in your building to make the most positive impact.  In a recent article by greentechmedia, Katherine Tweed makes the claim that the first step to using less energy is benchmarking, or simply taking account of how much energy you already use.  To Wattvisionaries, this may seem obvious, but it's true: simply monitoring how much energy you use can cut your energy bill down by 5% before even making any significant changes to your building.

Having knowledge of your energy consumption grants insights into how to reduce your power bill, lower your carbon emissions, and even meet standards set by the government. The demand for energy efficiency will continue to grow exponentially this decade, and "Building data analytics need to happen 'at every level and every sized building'". Wattvision makes it easy to perform energy monitoring on any scale; anywhere there's a power meter, we can get you your real-time data so you can charge confidently into your future energy changes.

Wattvision, Energy Monitoring, and Graphic Design

Wattvision employees are required to meet a weekly quota of time for fun and personal growth. To meet his quota, one of our programmers recently attended the "Graphic Design - Now in Production" exhibit on Governor's Island, NY. 

Our programmer was surprised to find a reference to his weekday life: real-time energy monitoring. Here are some snapshots from the interactive design section featuring some tablet format publications shown on ipads:

Although Google Power Meter might be gone, the problem of needing real-time energy monitoring has not gone away, and Wattvision has the solution.

Keep the feedback coming; if there's anything we can do to design better hardware or software, let us know!


nytimes gave the exibhit a positive review, and here's a neat blurb on youtube about them. (it's free!)


Avoid Huge Surcharges by the Power Company

Wattvisionaries across the country (and the world) have discovered a wide variety of applications for our energy monitoring hardware and software.  Nick Salvati Jr. of Cadillac Plating Corporation in Michigan has found a particularly practical use for Wattvision: using our e-mail alert system to make sure his company's energy use never peaks, giving him an inflated rate from the power company.

When you get the bill from your utility provider, it's often unclear what calculations were made to get to the bottom line.  Nick realized that his power provider was charging him more than triple for each kilowatt hour he used when the wattage in any of his buildings was over a certain threshold than when it was below that threshold.  Power companies institute policies like this to take advantage of the high energy needs of businesses, and before energy monitoring, there really wasn't much that someone like Nick could do to avoid getting gouged by the high prices.  

Enter Wattvision.  With our e-mail alert system, Nick can be notified in real time whenever his energy consumption rate goes over the power company's threshold, and then he can take steps to redistribute his energy consumption among his company's buildings or temporarily turn off certain equipment so he stays under the limit and never gets surcharges.  Viewing his live graph and history on our website, he can also look at trends in his company's energy use to help him make educated decisions about his long-term energy habits.  As a result of using Wattvision, Nick has been able to save thousands of dollars per month, all money that the power company would have previously taken from him. 

Do you really know what you're paying for? Find out your power company's policies and use Wattvision and you could get back a large chunk of your money!

Utah's Most Energy Efficient Home on Wattvision

University of Utah architecture professor Jörg Rügemer spent over a year crafting his home, 125 Haus, so that it would live up to his high standards for energy efficiency.  As a result, the Park City, UT house regularly consumes under $1 of energy per day and has been unofficially named Utah's most energy-efficient and cost-effective house.  

In addition, Professor Rügemer is a Wattvisionary, and 125 Haus consistently sits atop our Top Energy Savers rankings.  With 4 occupants and 2400 square feet of space, 125 Haus often manages to use under 2 Kilowatt hours of energy per occupant throughout an entire day.  Check out its live Wattvision graph here and learn more about the house from Jörg himself in this video

Wattvision's vision for the future is that someday everyone will live in homes this energy-efficient.  In the meantime, even though we can't all build our homes from scratch, we can certainly make steps towards improving our homes' energy efficiency by having proper insulation, checking up on our lighting, buying energy efficient appliances, and monitoring our changes with Wattvision.  Can you take the top spot from 125 Haus?

How to Eliminate Your Energy Bill Entirely with Wattvison

Last month we received the following e-mail from a Wattvision Customer:
I received the Wattvision monitor in February and have had large credits ever since. The Wattvision monitor helped me tweak the daily wattage use and this allowed me to take full advantage of our solar panels. I changed out all the bulbs in our bathroom vanities to compact fluorescent lights and installed timer switches in the kids bathroom to turn off the lights when they forget. I also found a lot of other things around the house sucking power and I put a stop to that. The Wattvision monitor has already paid for itself in the first 3 months and I now receive credits on my bills.



This story just goes to show how after as short of a time frame as 3 months, with a little bit of effort, experimentation, and Wattvision, you can cut down your energy bill so far that the power company could owe you money every month.   Take advantage of power company credits for environmentally-friendly energy usage and make the changes that can enable to you never have to pay an energy bill again!  Look for big energy-sucking devices in your home or business and consider replacing or modifying them to optimize your energy use at home. Save energy, and save money with Wattvision.