Tag Archives: efficiency

Home Solar Power: Getting Started

home solar powerA couple weekends ago I had to opportunity to attend a class entitled “Do It Yourself Photovoltaics” which was put on through our local garden center. The man who taught the class, Mr. Jon Passi, stressed that his goal was to make solar power projects as accessible as possible to others, and encouraged us to share what we learned from his class with our neighbors, so I’d like to share a bit about what I learned with you.

home solar panels 3

How Much Solar Power Do You Need

The first step to getting a home solar project going is to figure out how much power you need. Most power companies these days will provide graphs of your power use for the past year, so you can see how much electricity you use each month. When you look at this graph you’ll probably see that you have a season of the year where you use quite a bit of electricity, and a season where you use less. For my family, we use more electricity in the winter time than the summer, because we are more likely to be inside, and because it is dark during more of our waking hours. But if you might find that the opposite is true for you, depending on your habits and your home.

So, take a look at your energy use over the course of a year. With solar power, you produce the amount of electricity you use each day, and then start over again the next day. Figure out what your average monthly electricity use is. Then divide that number by 30 to get an estimate of your average daily electricity use. For the average American family, this number is somewhere in the range of 20 – 40 Kwh per day.

Your average daily electricity use is what you’re shooting to produce with a home solar power project. Yes, some days you will use more, but if you’re still connected to the power grid, you’ll be able to draw whatever extra you need from your power company. And on other days you will use less electricity than the average, and on those days you will be able to sell back any extra that you produce to the power company. It will all even out in the end, and usually in your favor – depending on your power company, you’ll be able to sell your extra electricity to the power company for more than you are paying for the little bit you need from them on cloudy days or days when your energy use is a bit higher than average.

home solar panels 2

How Much Will Home Solar Power Cost

The next step is to figure out if you can lower this number. Home solar projects are still pretty expensive, so the more you can lower your daily needs, the less you need to invest in supplying that power. Before you start shelling out dollars for solar panels, maybe it’s the right time to upgrade to a more energy efficient refrigerator, dish washer, or washer and drier. Maybe it’s time to commit to hang drying your clothes. Make sure your computer, television, and gaming systems are all on power strips that you turn off when you’re not using them to reduce the amount of phantom load your electronics are drawing. Upgrade your lightbulbs to LEDs. Before you spend $10k+ on solar panels, spend a couple months committing to lowering your energy use, and then recalculate your average daily electricity use.

A good rule of thumb right now for how much a home solar power project is going to cost you is to multiply your average daily electricity use by 1000. So if your home uses 22 Kwh of electricity per day, the cost of a project big enough to cover your entire energy needs would be about $22,000.

Before you get bug eyed at the cost of a home photovoltaic project, keep in mind that there are currently lots of opportunities for energy rebates. The federal government will give you 30% of the cost of the project in rolling tax breaks. (Rolling means that if you don’t use the whole 30% the first year, you can take the remainder the following years until you reach the full 30%.) Many power companies are also offering rebates for home solar projects right now as well. Mr. Passi gave us some examples of projects that he worked on in the past couple years, and many times the after rebate costs were around 60% of the total cost of the project.

Also, keep in mind that solar panels take up quite a bit of space. You likely won’t have enough room on your roof (especially in a city or suburb situation) to even install enough solar to cover the entirety of your daily use. When you look at how much solar power you can actually install on your house, the scope of your home solar power project may drop significantly. And even if you’re only supplying some of your home electricity needs, on sunny summer days, you will likely still produce quite a bit of extra electricity to sell back to the grid.

I have plenty more to share on this topic, but I think this is a good start for today. In the future I’ll get into more about the components you need for a home solar power project, and use our house as an example for figuring out how much electricity you need to produce and the costs of completing that project.

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Adding Insulation for Energy Efficiency part 2

The last time we checked in on the topic of insulation and insulating a house to the point where it wouldn’t need a furnace was back in December. Sheesh. The cold has broke here in the northern great lakes region, and while there is still a chill in the air some days, we seem to be headed right into spring. The good news is, insulation is not just a winter topic. Good insulation in your home will help keep it comfortable all year long. And keep your energy bills down. And so we forge ahead with adding insulation for energy efficiency.

Previously, I walked through the calculations to determine the payback period for adding insulation. Today let’s look at a couple of examples of how that might work our in practice.

  • R-value of the initial insulation (Ri)
  • R-value of the final insulation (Rf)
  • Cost of insulation (Ci)
  • Efficiency of the heat system (E)
  • Cost of energy (Ce)
  • Number of Heat Degree Days for the year (HDD)

And the equation looks like this:

P = (Ci * Ri * Rf * E) / (Ce * (Rf – Ri) * HDD * 24)

OK, take a deep breath. We’re about to do some math!

Example 1: Fiberglass Insulation Upgrade

For our first example, we’ll use the following situation: A house in Wisconsin is going to have its insulation upgrades. It currently has fiberglass batting with an R-value of 13, and will be upgraded to fiberglass batting with an R-value of 19. The cost of the new insulation is $0.41 per square foot. The house is heated by a natural gas furnace that is 85% efficient. The cost of natural gas in Wisconsin is $0.82 per therm, and 1 therm is equal to 100,000 Btu (British thermal units). The number of heating degree days for Wisconsin is 7499. We want to find the payback period for the new insulation.

So, breaking down our equation, we have:

Ci = $0.41 per square foot

Ri = 13

Rf = 19

E = 85% = 0.85

Ce = $0.82 per therm = $0.0000082 per Btu

HDD = 7499

P = (0.41 * 13 * 19 * 0.85) / ((0.0000082) * (19 – 13) * 7499 * 24)

P = 9.7 years

Wowza! That’s more time than I was expecting. So what are the key factors here that could cause this to payback period to go down? Well, first of all, with a little more looking, you might be able to find a better price on your insulation than a quick tour through the Home Depot website gave me. Also, natural gas in Wisconsin is pretty dang cheap right now, all things considered. But as more cities and states do things like ban fracking for natural gas, that cost could go up significantly, which would obviously bring the payback period down.

Example 2: Sprayed Foam Insulation – How much can we get?

What if instead of replacing all that R-13 fiberglass insulation with R-19 fiberglass insulation, we wanted to replace it with spray foam insulation?

Spray foam insulation has an R-value per inch of foam thickness. You can increase the total R-value by spraying a thicker layer of foam. There are tons of options available as far as spray foam goes, but for the sake of this example, we will use this Dow Froth Pack as our insulation. This spray foam provides R-6 per inch of thickness, so 1 inch has R-6, 2 inches has R-12, 3 inches has R-18, so on and so forth.

In this example, instead of calculating the payback period for the spray foam insulation, we’re going to see how thick of an insulation layer we can “afford” to apply, given the same payback period as the upgrade from R-13 to R-19 fiberglass. In other words, we are going to solve for Rf.

So, breaking down our equation, we have:

Ci = $1.01 per square foot

Ri = 13

Rf = x

E = 85% = 0.85

Ce = $0.82 per therm = $0.0000082 per Btu

HDD = 7499

P = 9.7 years

Through the magic of algebra, we can rearrange our equation to solve for Rf:

Rf = (P * Ri) – P – ((Ci * Ri * E)/(Ce * HDD * 24))

Which looks gross, but it’s really just a matter of plug and chug at this point:

Rf = (9.7 * 13) – 9.7 – ((1.01 * 13 * 0.85)/(0.82 * 7499 * 24))

Rf = 10.67, or about 1.75 inches thickness of the spray foam insulation.

So, for the same payback period as with the fiberglass insulation, we’d actually be downgrading from R-13 to R-10.67 with the spray foam. If we wanted to increase to the equivalent R-value, our payback period with the spray foam would be nearly twice as long!

But then what’s all the fuss about spray foam insulation? Why would anyone use it if the return on investment is apparently so low? Well, the R-value of the insulation isn’t telling you the whole story here. Remember the walls of your house are not just made out of batts of insulation. There is also the framing, the siding, the sheet rock, and all the other layers to consider. And those layers typically have small cracks and crevices where the heat can leak quite easily. One of the benefits of the spray foam insulation is that it fills in and seals all those leaky spots. So not only do you have the impact of the insulation layer, but you’ve increased the insulation abilities of all those other layers as well. Insulation can be one of those things were whole is greater than the sum of the parts.

Onward, Energy Efficiency Warriors. Next time we visit this topic we’ll get to the big finale: Can you insulate a house enough such that you don’t need a furnace???

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The Energy Efficiency Project: Month 2

January 13th – February 12th, 30 days

This month we mostly spent our time picking paint colors, getting started with the painting, figuring out where our stuff should go, and getting our compost started. As far as energy efficiency initiatives went we:

  • Replaced a dead CFL light bulb with an LED bulb
  • Turned the thermostat down from 68° F to 66° F
  • Checked the air filter on our furnace to make sure it was new/didn’t need to be replaced. It was still clean, so we didn’t replace it.

This month’s upgrade cost: $8.82

Total upgrade cost to date: $8.82

So, we didn’t expect too much of a difference in our energy usage this month. Now let’s look at the numbers!

Over 30 days we used 427 KWH. Which comes out to an average of 14.2 KWH/day. This is actually slightly higher than the 14.0 KWH/day we used during our last billing period. Womp womp.

I’m guessing this is due to putting up some post-Christmas holiday lights which are not LEDs. I know, I know, but here’s the thing. We still have these strings of working fine holiday lights, and I can’t bring myself to replace them until they no longer work. Use what you have, right? We also started some citrus tree seedlings, and had them germinating on a heating pad 24/7.

We are part of the Alliant Energy Second Nature renewable energy program, at the 100% level. (In this program you can choose the amount of your energy use that you want to be matched in renewables, and we chose 100%.) So the cost of our electricity is $0.13 per KWH, for a total of $55.90.

We also used 80 Therms of natural gas heat energy. Which averages out to 2.7 Therms/day. Definitely less than the 3.1 Therms/day we used during the previous month! Dropping the temperature on our thermostat made a difference, and really the only way it affected our lifestyle is we that we wore slippers around the house more often. Also, looking at degree days this month compared to last month: 1286 vs. 1211. Even though this months number is a bit larger than last month’s, this month’s bill was for 30 day and last month’s was for 27 days. This means that our furnace didn’t have to work quite so hard to heat our house this month, which also helped out with reducing our gas use.

The natural gas market fluctuates in Wisconsin, so there is not an easy dollar per Therm number to give you, but during this billing period we paid $65.99 for our gas use.

Our energy bill also provides these numbers for helpful comparison:

Electricity used this month last year: 744 KWH

Gas used this month last year: 97 Therms. Average temperature this month: 22° F. This month last year: 10° F. So last year was quite a bit colder than this year.

Degree Days this month: 1286 vs this month last year: 1652. Degree days are the number of degrees below 65° F in one day, all added together for the total 30 days of the billing period.

Want to previous months of the Energy Efficiency Project? Here is Month 1.

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Introducing The Energy Efficiency Project

Once upon a time, husby and I thought, what if we bought a house in the small town we’ll be moving to this spring. About a year ago, when I first starting envisioning this whole building earth project, I thought a good progression would be to have a house to demonstrate some of the energy efficiency, green building, and sustainable design ideas that I’ve been writing about. Not to mention we were ready to start investing in our own place inside and out.

One of the projects that I’m super excited about starting in regards to our new house is this series on The Energy Efficiency Project. Each month I’m going to explain what things we’ve done to reduce our houses energy use: upgrades, downgrades, or behavior changes. And then I’ll share the nitty-gritty with you: our monthly energy bill, and the costs, and pros and cons of the changes we’ve implemented. My goal is to be as transparent as possible in how we use energy and how we are attempting to save energy. My hope is to show how small changes can add up to significant energy savings, and maybe you’ll be inspired to adopt some of the same changes yourself.

power lines: the energy efficiency project

So first, let me share some details about our new home to give you the lay of the energy use land.

Size: 1,026 square feet. Single story, with an unfinished basement, rafter attic for insulation.
Energy using appliances: refrigerator, stove, washer, dryer, hot water heater, gas furnace, central air, garage door, coffee grinder, exhaust fan
Electronics: computer, cell phones, alarm clock, seedling starter heating pad
Light fixtures: 21 bulbs worth
Windows: approximately 100 square feet, most of which are fairly new with aluminum sills
Insulation: I’m not sure exactly, since I haven’t looked inside the walls yet, but I’m pretty sure it’s just your basic fiberglass batts. The attic has about 3-4 inches of blown insulation covering the house.
Occupants: 2 adults, one wee tender babe

The Energy Efficiency Project: Month 1

We’ve been living in the new house for about a month now. Long enough to get our first energy bill! So we have a bit of a baseline to start with.

For December 17th through January 13th this is what our energy usage looked like:

Over 27 days we used 379 KWH (kilowatt hours) of electricity. We are part of the Alliant Energy Second Nature renewable energy program, at the 100% level. (In this program you can choose the amount of your energy use that you want to be matched in renewables, and we chose 100%.) So the cost of our electricity is $0.13 per KWH, for a total of $49.62.

We also used 85 Therms of natural gas heat energy. The natural gas market fluctuates in Wisconsin, so there is not an easy dollar per Therm number to give you, but during this billing period we paid $72.90 for our gas use.

Our energy bill also provides these numbers for helpful comparison:

Electricity used this month last year: 834 KWH (!!! what did the former owners have plugged in that sucked more than twice as much electricity as we used?)

Gas used this month last year: 96 Therms. Average temperature this month: 20° F. This month last year: 14° F. So last year was a bit colder than this year which explains the higher gas usage.

Degree Days this month: 1211, vs this month last year: 1698. Degree days are the number of degrees below 65° F in one day, all added together for the total 27 days of the billing period

Now let’s see where we can go from here!

P.S. Interested in seeing a picture tour of our new house? You can check that out over on macnamania.com!

Happy 2015

Happy 2015Happy 2015!

How’s it feeling now that you’ve had a week to break it in?

Let’s start this year off with a bang: We bought a house!  Due to job related circumstances we will only be living in the house part time between now and June, and we will spend the rest of our time in our current apartment. This will provide us with plenty of time to get some updates and projects done before we move in for good this summer.

Now you might be wondering, what does this house have to do with this little blog? Well, it means that as we do house renovation projects, I’ll have plenty of opportunity to share with you all of those green building home renovation projects, like:

  • What are the most earth friendly paints, stains, and adhesives to use?
  • Which are the most sustainable flooring materials?
  • How do you go from lawn to organic garden (hopefully without your neighbors giving you the side-eye)?

Another blog series that I have in the works is on making a house more energy efficient. I’ll take a look at the energy usage of this house, and similar sized houses in the neighborhood, and do monthly updates on what we have done to bring that energy use down.

Aside from the house, in 2015 I’ll be continuing the series on “green” certifications in the construction and home furnishing areas. I’ll also continue to explore passive house design, integrative design, green living habits, and compost.

If there is anything you’d like to see in the upcoming year, be sure to leave a comment or drop me email.

I know I’m excited for everything that 2015 has to bring! I hope your new year is starting out shiny and bright and not too cold!