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Heating strategy to take advantage of off-peak electrical power rates

Joel Cooper | Posted in General Questions on

I am planning to have a house built later this year. I plan to use electricity as the main source for heat. I live in the Province of Ontario and they will introduce time-of-use pricing in 2012. What is the best strategy to take advantage of off-peak rates?

– I live in climate zone 7A
– house will be 24×32′ – 2 floors – unheated crawl space
– it will be inspired by Passive House but will not meet all the standards
– I am retired so I will have time to feed a small wood stove during the day but will need a heating system that can maintain a reasonable temperature when no one is at home or when not using the wood stove
– passive solar heating possible during afternoon hours but it is often cloudy here during the winter months
– I don’t need air conditioning in the summer
– in my rural/remote location, natural gas is not available; fuel oil is inconvenient to deliver (plus I want to avoid fossil fuels); ground source heat pump is not an option; local electrical utility company generates 100% of their power from water and wind.
– time-of-use pricing: off-peak rate of 5.1 cents/kWh (plus about another 6 cents/kWh for delivery and other overhead charges) will be from 9 pm to 7 am weekdays and 24 hours a day on weekends.
– how can I take advantage of the off-peak rates to store heat generated from electricity and release it to the house from 7 am until 9pm?
– options I have been considering are: 1) electric water heater/radiant floor system or electric cable floor system in a lightweight slab on the first floor; 2) electric thermal storage heating unit(s); keep it simple and just use baseboard heaters because a well-insulated house will not need expensive heating infrastructure; or is there another strategy?
– and then consider this situation: I am increasing my investment in the local electrical utility company (they are currently paying about a 6% dividend) and the dividend will pay my electrical power bill!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Joel,
    You have lots of options.

    First of all, a ductless minisplit air-source heat pump will be two or three times more efficient than electric resistance heat. If you build a tight home with lots of thermal mass, you can turn up your thermostat at night so that your home is 72 to 74 degrees by morning, and then shut off the heat during the day. Even if the indoor temperature drifts downward, you would still be comfortable -- you can always put on a sweater in the evening.

    If you want to use electric resistance heat, they used to make electric heaters with integral bricks. The electric elements were activated at night, and the bricks stored the heat into the daylight hours. A fan blew air over the bricks. Somebody must still make those.

    You could also pour a slab to provide thermal mass, and install electric resistance radiant floors in your bathrooms. These could be turned on at night to warm up the slabs, which would stay warm for hours.

    Or just buy a couple of big electric water heaters, put them on timers, and circulate the hot water through baseboard units.

  2. Douglas Horgan | | #2

    If you could find some way to use a heat pump to warm water, i.e. air-to-water or ground-loop-to-water, you could put in a couple of storage tanks and run the heat pump at night.
    I know you could do it with off-the-shelf geothermal stuff, though your well would cost an extra $5-10,000 depending on capacity required. There are air-to-water units out there but they're kind of experimental in the first place (or new to the market anyway, which is the same thing in my experience), and Ontario is not the ideal climate for them to begin with.

  3. Jack Woolfe | | #3

    If you want to use electric resistance heat, they used to make electric heaters with integral bricks. The electric elements were activated at night, and the bricks stored the heat into the daylight hours. A fan blew air over the bricks. Somebody must still make those.

    I heat my house with Stiebel Eltron Electric Thermal Storage (ETS) heaters, using the cheaper night rates. Don't know if they still make them. This URL suggests they still supply parts for them: http://www.stiebel-eltron-usa.com/contact.html

  4. David Meiland | | #4
  5. Kevin Dickson, MSME | | #5

    Make sure you compare the true cost of on-peak electricity to your off-peak rate. You're paying $0.11/kwh off peak (which ain't that great). Unless you're paying, say, $0.17/kwh on peak, then the hassle and risk isn't worth it. The risk is that when you're on off-peak pricing, you pay a much higher on-peak rate than if you stuck with the flat rate.

    Nationwide, off-peak and demand rates aren't the bargain they once were.

  6. Joel Cooper | | #6

    Thanks everyone for feedback. I will do some more homework on the suggestions to see if they meet my objectives.
    The ductless mini-splits are new to me and I will need to do more research. I understand that their main use is for air conditioning. I have not needed air conditioning in the previous 29 years I have lived at my building site (I live on the shore of the world's largest lake and it provides a form of natural air conditioning) plus their performance diminishes in cold temperatures (we have had 6 nights below -15F and as low as -33F so far this year). But maybe they are worth checking out.
    I discovered electric thermal storage heaters late last year when I heard that a city in Ontario was offering rebates for homeowners buying electric thermal storage heaters. I will check these devices further.
    I am avoiding geothermal for many reasons, but a water storage tank system may be worth checking out.
    I do not have a choice on variable electricity rates versus flat rates. Ontario is making variable rates mandatory for everyone.
    Once I get a better handle on the heating requirements for my new house, I can evaluate the cost of these mechanical systems versus simple baseboard heaters and maybe electric cable in-floor heat in the bathroom and kitchen (a plumber told me to check out electric cable heat and a person in the electrical industry told me to avoid electric cable heat and to use hot water heat???). If I go the simple route, I could put the cost savings towards even better windows or more insulation.
    The trend to higher cost of electricity and variable time of day pricing produces 2 actions: try to shift one's energy use to off-peak times or just use less electricity through conservation (like an airtight, well-insulated house). The best heating strategy will become clearer as I continue with my house planning.

  7. Kevin Dickson, MSME | | #7

    Do you have a link to the pricing regime you'll be dealing with?
    Often, the utilities throw in a demand meter with TOU, which means you may also need to reduce your kilowatts, or your peak power draw.

    And keep in mind that the Smart Grid is coming, and you may be able to automate the timing functions:

    http://greenbuildingindenver.blogspot.com/2010/08/smart-grid-city-update.html

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