Perhaps a sad and ironic commentary on modern times is the decline of energy devoted to cooking. Residential cooking energy has decreased to one-third of its level three decades ago. That would seem to be a good thing….a decrease in energy consumption. Unfortunately, it is most likely due to less healthy, prepared food choices coupled with more frequent driving to “eat out”. The gallon of gasoline required to start a car, drive a few miles to a restaurant, and then return home could have cooked many meals (a gallon of gasoline is about 130,000 Btu; a burner on a cooktop is about 5000Btu/hr, for about 26 hours of cooking time).
Equinox House is occupied by Deb Newell, one of the finest culinary artists around our area. Even though only Deb and Ty live in the house, her cooking activities have not diminished as their four children left the nest (as their wastelines can attest). As such, we are able to collect a lot of information on cooking.
The bargraph below shows December’s cooking energy relative to the other house energy systems. The monthly total energy (1777.2kWh) includes the solar system production for the month. The house energy usage was 1500kWh. December was a near record cold month with record snowfall. It is also a month with a lot of cooking during the holiday season. The bargraph shows that approximately 70kWh (double oven [54.7kWh] and kitchen cooktop [two circuits for a total of 13kWh]), or 5% or Equinox House energy usage went to cooking.
Of course, cooking in the winter helps heat the house, so one gets “double duty” from this in the winter. Part of the puzzle of piecing these energy flows together is that if no cooking occurred, we would still find that the total energy for the house would be 1500kWh because heat for keeping the house comfortable would have to be supplied from somewhere. If the heat comes from a heat pump rather than cooking, however, as in Newell Instruments’ CERV, the 70kWh of heat from cooking would have required ~35kWh of electricity, so one must assess the various manners in which energy is delivered. As summer comes around, it’s time for gespaucho.
The more important aspect of cooking are its peaks and valleys of power consumption. The two following plots show Equinox House power demand on a typical weekday with a bit of cooking, and on the most extreme cooking day of the year….Thanksgiving. Even though the “energy” required for cooking is small, the power required is the largest in the house. This is like the muscle cars of the 70′s with excessive horsepower used only for short bursts accelerating from a stop light.
Typical weekday (January 17, 2011) power usage. Kitchen usage in the morning and evening cause the peak power levels.
Thanksgiving, November 25, 2010 with daylong cooking activities and 14 people in the house all day long. Around 5pm as the cooking built to a crescendo, we could have used Scotty and his di-lithium crystals for more power (Star Trek fans will understand).
Our record power draw was on Thanksgiving, and most likely many other people were doing the same thing. This requires our utilities to bring up “peaker” plants in order to supply the energy needed for these short bursts. Energy from peakers is more expensive for a number of reasons. The important aspect as far as house design is concerned is the measurement of this power demand so that other strategies (eg, “Smart grid” controlled appliances) can be implemented as regulations and utility costs impact one’s ability to use as much power at any time as is currently the case in most of the US.
