Improving Our Home’s Energy Efficiency

I recently gave Centerpoint Energy a ring and asked if they could pull the records on what Carly and I have been paying for natural gas used in our home over the time we’ve owned it. CenterPoint provides up to 15 months of data on their website (login required) but will print and mail larger data sets.

Once I received the thick envelope of data and returned it to an electronic format, I created this year over year look at monthly costs:

Gas Payment by Month

Ideally, I’d like to see the red line (Year 2) below the blue (Year 1) with the Gold line (Year 3) below the red. To achieve that, I need to progressively decrease what I’m paying CenterPoint Energy for natural gas.

Uses of Natural Gas

I believe this is a complete list of how natural gas is consumed in my house. I’ve tried to rank them based on how much natural gas I perceive each system consumes annually.

1. Furnace to heat water for baseboard water heating
2. Hot water heater
3. Clothes Dryer
4. Stove/Oven
5. Gas Grill

Cost Cutting Actions

Over time, we’ve made a few changes around the house that I assume helped lower our natural gas consumption, but the feedback loop isn’t as precise as it is with the Google PowerMeter used for monitoring electricity. Here’s what I think has helped.

Water Heater Blanket – I don’t think we’ve reduced the amount of cooking, grilling or laundry we’ve done in summer months, so the drop may be tied to the water heater blanket I purchased and installed in April 2009. I paid $26.21 for that at the time, so it may have paid for itself in only a few months. If it cut my gas costs by as little as 10 cents/day, it’s already paid for itself.

Door Sweeps – When we moved in, you could literally see light entering the house from below the doors. Closing the obvious gaps with door sweeps cost less than $40.

Expanding Foam Sealant – $5 spend on this stuff helps close drafts in tough to patch areas. For example, our front door has a skeleton keyhole that would shoot air into our home that’s 100F colder than indoor temps on coldest days. A few cents worth of foam shut that down. Don’t get this stuff on your hands.

Attic insulation – I found Owens Corning’s attic insulation calculator valuable for determining how much insulation my attic could use. Since there was already stuff up there, I picked up around 14 rolls of R-30 insulation to roll out on top of what was there. My total cost of supplies (including a face mask, gloves, and box cutter) was under $200. Rolling out the insulation took around 3 hours. I was itchy for a day after that. Before do-it-myselfing this, I also got a quote from a company that would blow in insulation. That was $2,000 rather than $200.

Programmable Thermostat Adjustments – I can’t imagine not having a programmable thermostat in a house these days. They’re cheap and help save a ton of energy since you’re only using as much energy as you need to be comfortable at any time of the day or week. The cost from $25-$100 depending on how complex a model you’d like (I use a relatively simple 5-2 model where it has one setting for weekday wake-up, mid-day, evening, and overnight temps and a second setting for the weekend routine). We got a bit more aggressive with our overnight low temp this year, which probably accounts for some of our more recent savings. At this point, our overnight temp is “chilly on the couch but perfect for sleeping” with the heat ramping back up starting early enough in the morning to make crawling out from under the covers comfortable. Then it drops off during work hours. Painless savings.

Like I said earlier, it’s tough to correlate individual projects with energy savings since the feedback loop on gas consumption is so poor. What I do know is that we spent $269 less in our second year in our home than the first on natural gas. We saved around 315 therms worth of natural gas. Converting that to a car gasoline’s energy (btu) equivalent, we burned 252 gallons less gas without compromising on comfort. Good stuff.

11 thoughts on “Improving Our Home’s Energy Efficiency”

  1. In preparation for the baby which is due to arrive soon and the mandate that the house be at 68 all the time for it, I set the thermostat at 68 since we had to turn the heat on. Before that time we were using the programmable thermostat to keep the house at 63 during the day and 69 to 70 when we were home.

    I don’t know if it’s because natural gas prices have gone down or what, but our bill (we’re on the budget plan) was reduced from $26/month to $21. If it wasn’t the price of natural gas that caused the big monthly drop, then it was the steady 68.

    I heard once, and ignored it because I thought it was crazy, that it costs more money to let your house cool down and then heat it back up to a comfortable temperature than it does for it to remain at one steady temp. I may have proven that theory in my own home 🙁

  2. Bill, good point about the price fluctuations. I wasn’t able to get historical therm data, which would be a better metric to use.

    The only way it would make sense for it to be the same or cheaper to keep a home at a constant temp would be if your house had no heat loss, which is impossible.

  3. A monthly chart of BTU use would be more interesting (though I’m glad you mentioned it at the end). Also, you have to cross-ref that with outdoor temp, which has a big effect on indoor heating demand.

    Still, I don’t doubt all the things you did were great. I’m a energy-data geek too, and need to hammer down a bit on our electricity use (vampire appliances).

  4. I’ve been tracking my home’s energy use as well for the past several years. I’ve been able to make some progress on using less energy.

    I’ve also heard the idea that you’re better off trying to maintain a constant temp than to let it fluctuate. My own experience is contrary. The energy savings I’ve seen in my home are due almost entirely to the programmable thermostat and the way we let the temp drop as low as 50 during the day and overnight. It also probably helps that our house is tiny and heats up very quickly.

  5. I’m lucky enough to be in the Excel pilot area that runs a few miles on either side of the Central Corridor, which means for $30 I got a visit from a Neighborhood Energy Connection team, installing all the CFLs I can use, a hot water heater blanket, door sweeps and weatherstripping, a blower door test… and I could have gotten a programmable thermostat except we already had one. What a deal.

    Plus they helped me figure out which things in my house were drawing the most electricity, including checking for phantom load on Mac laptops (the answer – if fully charged, there is none).

  6. I’ve kept track of my therms and cost of heating my house for the past few years as well. Haven’t really done much outside of a programmable thermostat, but have noticed a few improvements. Though I’m starting to agree with Bill in that a constant temp might be best. Isn’t it kinda like the old computer debate? Better to leave it running over turning it on and off?

    Here is some therm to cost ratios over the past few years.

    2/7/08 203 216.22
    3/4/08 202 232.89
    2/6/09 213 213.01
    1/8/10 200 188.61

    Looks like cost is way down over the past few years

  7. I tried to install a water heater blanket a month ago and it so happens that our water heater is situated about a half inch too close to the wall to get the blanket all the way around. I didn’t feel like trying to manage multiple cuts and extra duct tape, so I ended up ditching it all together.

    Love the programmable thermostat, too. Our townhouse is pretty well insulated, so we don’t have a whole lot of leakage, but we addressed our biggest issue by putting up plastic over the windows which has clearly made a difference.

    When we finally buy our next house in Minneapolis (which I’m sure will probably be an older one), I’m expecting to have to do a lot more work on insulating.

  8. Got a programmable thermostat and set it to 62 while we’re awake and 60 while we’re at work or sleeping.

    Not too bad and it keeps the gas bill reasonable. No barefeet or t-shirts, but I mean come on this is MN and it is winter.

    I’ll bump it up if I come in from snowmobiling or other winter activities but only for a quick warm up.

  9. The first thing I did when we moved in to our now-111 year-old house was to buy a programmable thermostat. Before our first full winter I blew in about 40 bags of cellulose insulation in the attic which had only 3 or so inches of vermiculite insulation in it. I turned down the temperature of the water heater a bit – 120 degrees is more than hot enough – and have been slowly replacing windows while making sure that the historical moulding stays in-tact. Even with a 15 month-old in the house, the thermostat still goes down to a brisk 58 degrees overnight and she hasn’t come down with a raging case of pneumonia yet. Over time, though, I’d like to insulate the walls because not doing that is just pissing money away.

  10. I’ve done a fair bit on our 1930’s house, including insulating the outside walls and the attic, insulating water pipes (not the heater itself, yet), and turning the heater down a bit.

    I also went on a rampage against electricity use.

    The results have been fairly striking, documented at http://sandeen.net/home-energy.html

    -Eric

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