What Makes an Oven Eco-Friendly?

Question

I am currently in the market for ovens and I wanted to know what makes on oven eco-friendly, whether it's electric or steam, without compromising reliability. I want a oven that not only benefits me but the planet as well.

Answer 1

If you are able to heat the oven from a renewable source (like solar energy, wood, biogas), this would be most efficient way to do it in terms of CO2-emmissions.

Often, this is not possible. Then you have to choose basically between an electical and a gas stove. In this case, a gas stove is best, as long as less than 70% of electricity comes from renewable sources. This is only a rough estimate, resulting from the fact that approx. 30% of primary energy used in combustion power plants arrive at your plug at home (due to losses in transformation and transmission).

By the way, a gas stove is also more economic, at least in germany. Here, one kWh of heat from gas costs approx. 10ct, electricity is at 30ct/kWh.

Answer 2

First of all, if you really want to cook green you should buy neither and instead go for a solar oven or solar cooker (more info on this on Wikipedia). However, if you live in a place where it is often cold and clouded then this isn't very practical.

Now, back to your question about ovens. There are two ways of looking at this:

1. How much energy and other resources are used to manufacture the oven
2. How much energy does the oven use when cooking

As for the first point; I don't know much about how ovens are manufactured. I suspect that the manufactering process isn't that different for the different types of ovens (electric, gas or steam), but I may be wrong. Perhaps someone else here can provide more information about this.

Energy efficiency:

First thing to consider is the size of the oven. Bigger ovens tend to consume more energy, so it's important to buy just the right size for your needs.

The type of oven is more complicated; it's difficult to find evidence that a certain type of oven uses less energy than another. One of the few numbers I found is the following table in this pdf about cooking efficiency for restaurants.

                                                   | Cooking  | Energy
Cooking method                                     |efficiency| factor
-------------------------------------------------------------------------
Microwave                                          |  57.5%   |  57.5%
Electric, self cleaning, convection                |  17.1%   |  13.4%
Electric, self cleaning                            |  13.9%   |  10.2%
Electric, standard                                 |  12.1%   |  10.9%
Gas, electric ignition, self cleaning, convection  |   8.7%   |   7.4%
Gas, electric ignition, self cleaning              |   7.1%   |   5.8%
Gas, electric ignition                             |   6.1%   |   5.8%
Gas, pilot light                                   |   5.9%   |   3.5%

Cooking efficiency is the fraction of the energy supplied to the unit that heats food
during a typical cooking cycle. Energy factor is the ratio of energy that is effectively
used to heat food to the total energy used.

I'm not sure how exactly they drew up these numbers and if it also applies to home usage. Sadly, there is no information here about steam ovens. I've heard that steam ovens are more energy efficient than electric ovens, but the only references I can find at the moment are the claims of appliance manufacturers (e.g. this one) and they don't provide any proof for this.

Answer 3

Choosing when you use your oven may be more impactful than which type of oven you choose. Here is a simple guideline worth trying: Cook more in the winter, less in the summer.

The "wasted" heat energy not applied to the food does not disappear, but dissipates into your house. In the winter this theoretically reduces the burden on your heating system. But of course it will increase the burden on your cooling system. My mother would always open the oven door so that the heat was not wasted. In reality, you don't need to open the door, since the heat will escape eventually.

This principle applies to lighting and other electronic devices contained within the envelope of your home. Most of the electronic energy is converted to heat dissipated within the home.