You cost the oven in three steps: find what one hour of oven time costs you, add the preheat, and share it across the day's bakes according to how many minutes each one takes. Then divide each bake's cost by the pieces it produced. For a tray of brownies it is often less than a cent each; for a few loaves or an oven run at half capacity, it is real money.
Find your cost per oven hour
Electric oven
Read your electricity meter before you switch the oven on and after you switch it off, at a time when other big appliances are not running. The difference is the kWh it used. Multiply by the price per kWh on your bill.
It is worth splitting the preheat from the baking. Read the meter when you switch on, again when the oven reaches temperature, and again at the end of the bake session.
Do not multiply the power rating on the oven's plate by the hours. The thermostat cycles the elements on and off, so real use is usually lower than that figure. Measure it.
Gas oven
Read the gas meter the same way, or, if you use bottled gas, note the date you connect a new cylinder and the oven hours until it runs out. A cylinder that costs $40.00 and lasts 20 oven hours works out at $2.00 an hour. If the same gas feeds your hob, log those hours separately or give the oven its own cylinder for a week or two.
Do not forget the preheat
The oven uses energy while it heats up with nothing inside. The products you bake afterwards have to pay for it. The fair way is to share the preheat across all the day's bakes, in proportion to the minutes each one takes. That way the bake that holds the oven longest carries more.
Worked example: a baking day
A normal baking day in your kitchen. Your meter readings showed:
- Preheat: 30 minutes, 1.5 kWh
- Baking: 3 hours, 6.0 kWh, so 2.0 kWh per hour
Say your bill shows $0.25 per kWh (use yours). Then the preheat costs 1.5 × 0.25 = $0.375, and baking costs 2.0 × 0.25 = $0.50 an hour, which is $0.00833 a minute.
Three bakes, one after another:
- Sourdough: 45 minutes, 6 loaves
- Brownies: 30 minutes, 2 trays of 24 = 48 brownies
- Granola: 40 minutes, 3 trays = 6 jars of 500 g
That is 45 + 30 + 40 = 115 minutes of baking. The preheat is shared: sourdough 45/115, brownies 30/115 and granola 40/115 of $0.375.
| Bake | Minutes | Baking energy | Share of preheat | Total | Pieces | Per piece |
|---|---|---|---|---|---|---|
| Sourdough | 45 | $0.375 | $0.147 | $0.522 | 6 loaves | $0.087 |
| Brownies | 30 | $0.250 | $0.098 | $0.348 | 48 | $0.007 |
| Granola | 40 | $0.333 | $0.130 | $0.463 | 6 jars | $0.077 |
| Total | 115 | $0.958 | $0.375 | $1.333 |
How each number is worked out: baking energy = minutes × $0.00833; share of preheat = $0.375 × minutes ÷ 115; per piece = total ÷ pieces.
What goes into each product's cost:
- Sourdough: about $0.09 per loaf.
- Brownie: less than a cent. Per tray, 0.348 ÷ 2 = $0.17.
- Granola: about $0.08 per jar.
What a half-empty oven costs
A large part of the energy goes into heating the oven and holding it hot, whether it has one tray or four. That is why the cost per piece jumps when you bake little.
On a Tuesday you get an order for 2 sourdough loaves and switch the oven on just for that: preheat $0.375 plus 45 minutes $0.375 = $0.75. Over 2 loaves that is $0.375 per loaf, against $0.087 on a normal day. More than four times as much.
With small numbers like these it can look trivial. Check your own: with a bigger oven, a higher tariff or a longer bake, the same pattern can add up to dollars per day. Two habits bring the cost down without changing any recipe:
- Group your bakes: one preheat, several bakes back to back.
- Move small orders to the days you are already baking, or fill the oven with something that sells.
Product cost or overhead?
You can put gas or electricity into your monthly overhead and spread it across everything you sell. The guide on how to allocate overhead to products explains that method.
In a bakery it is usually better to cost it per bake, because products do not use the oven equally. A loaf that holds the oven for 45 minutes and a brownie tray that holds it for 30 should not carry the same share. If you spread it by sales, the quick bakes pay for part of the slow ones. The guide on how to calculate the cost of a loaf of bread shows where this number sits alongside flour, time and the bag.
The oven is also your time
While the oven preheats and bakes, you are in the kitchen. That time costs money too, and usually far more than the energy. If you fire up the oven for 2 loaves, on top of 75 cents of electricity you spend well over an hour on a small sale. The guide on setup and cleanup time shows how to count the time nobody writes down.
Do it with the calculator
In the food cost calculator, enter your cost per oven hour and the minutes and pieces for each bake; it gives you the oven cost per piece to add to the rest of your recipe.
Frequently asked questions
How much electricity does a commercial oven use?
It depends on the oven, the temperature and how often the door opens. Read your meter before and after a bake day; that number is yours and beats any average.
Does a full oven use more energy than one tray?
Somewhat more, because it heats more dough, but a large part of the energy goes into bringing the oven up to temperature and holding it there, whether it has one tray or four. That is why each extra tray in a bake costs far less than a separate bake.
Is it worth costing the oven if it is a few cents per item?
Yes, for two reasons: on long bakes with few pieces, like loaves or whole cakes, it is no longer cents, and the calculation shows how much a half-empty oven costs you.