• Posts
  • RSS
  • ◂◂RSS
  • Contact

  • Rough Marginal Costs

    April 6th, 2014
    money  [html]
    We pay for most things directly as we use them: to park at a meter you put in quarters; to rent an apartment you send a check each month. For some things, however, our usage is metered and we pay after the fact: electricity, gas, water. In these cases we're often not well calibrated for marginal cost, which means we're not in a good position to make tradeoffs. Can I leave the fan on all night? Should I worry about letting this frozen food thaw in the fridge before I put it in the oven? How much should I be trying to take shorter showers? Colder ones?

    I thought it would be useful to compile some rough costs of these pay-later activities:

    Gas Oven one hour $0.16 [1]
    Gas Dryer one load $0.35 [2]
    Front Loading Washer, Warm one load $0.39 [3]
    Cold Shower ten minutes $0.57 [4]
    Hot Shower ten minutes $0.76 [5]
    Dishwasher one load $0.31 [6]
    Microwave two minutes $0.01 [7]
    Box Fan overnight $0.17 [8]

    This is based on a marginal cost of electricity of $0.21/kWh, natural gas of $1.40/therm, and water of $0.017/gallon which includes the sewer charge. [9] These come from our current bills in Medford MA; it's probably cheaper in lower cost of living states.

    While these are approximately in line with what I'd thought, I do see two changes I should make:

    • Be willing to use the dryer when line drying is inconvenient. (Previously I never used the dryer, for cost reasons.)
    • A long cold shower (in summer) is actually more expensive than a short hot one.


    [1] Gas Oven, 0.112 therms per hour.

    [2] Gas Dryer, 0.21kWh to spin the drum and 0.22 therms to heat the clothes.

    [3] Front Loader, 0.26kWH to run the machine, 0.064 therms for the water heater to heat the incoming water, 14.7 gallons of water.

    [4] Cold Shower, 3 gallons per minute, 30 gallons total, $0.57 for the water.

    [5] Hot Shower, 0.00014 therms per gallon per degree F. Ground water at around 55F, shower water at around 100F, so a 45F rise. Shower flow of about 3 gallons per minute. So over ten minutes that's thirty gallons each heated 45F. So $0.57 for the water [4] and $0.19 to heat it.

    [6] Dishwasher, 4 gallons of hot water and 1kWh to run the machine. That's $0.10 for the water and heating [5] and $0.21 for the electricity.

    [7] Microwave, 0.024 kWh per minute.

    [8] Box Fan,100W.

    [9] This is much higher than I'd thought, 10x the cost of desalination.

    Comment via: google plus, facebook

    Recent posts on blogs I like:

    Fireside Friday, November 27, 2020

    Hey folks! Fireside this week. A bit of a change-up in terms of the coming attractions. I had planned to start “Textiles, How Did They Make It?” next, but I want to do a bit more reading on some of the initial stages of textile production (that is, the pr…

    via A Collection of Unmitigated Pedantry November 27, 2020

    Building Depth and Window Space

    How much window space does an apartment need, relative to its area, and how does this affect building style? A fascinating post from about a year ago on Urban Kchoze makes the argument that modern North American buildings are too deep – Simon calls them o…

    via Pedestrian Observations November 27, 2020

    Thoughts you mightn't have thunk about remote meetings

    Welcome to this week's edition of "building a startup in 2020," in which all your meetings are suddenly remote, and you probably weren't prepared for it. I know I wasn't. We started a "fully remote" company back in 2019, but …

    via apenwarr November 23, 2020

    more     (via openring)


  • Posts
  • RSS
  • ◂◂RSS
  • Contact