Maggie Lane comments;

‘Lacking an oven of their own or unable to afford the fuel to light one, poorer people, such as the Bates, often sent their pies to be baked by the local baker (marking them with intials for later identifcation: ‘pat it and prick it and mark it with B.’)

The apples were ‘baked all night in the still warm oven of a stove that has been heated all day by a coal fire. In the morning the oven would be cold.’ 
Bakers like Mrs Wallis would thus gain a few extra pence from the residual heat of their ovens. The minimum amount of heat remaining in the oven may explain why Miss Bates had her apples baked twice to reduce them to a pulpy state.

There was a great deal of prejudice against eating raw fruit through the Eighteenth century, a feeling Mr Woodhouse condones.

-M. Lane. ‘Jane Austen and Food’, p.67.

It appears the bakeries did this as a service for the poor. I’m guessing it cost Miss Bates perhaps twopence a week to have her pies cooked in the residual heat of the local baker’s oven. 

Apparently the genteel poor like the Bates had a fireplace instead of a stove or oven. 

Taking the cost of fuel into account, it is possible you required an income of at least 5-6,00 pounds per year to own a stove.

The only info. I can find on stoves and open fires comes from A Jane Austen Cookbook by Peggy Hickman. pp15-17.

Apparently when the Austens were at Steventon, cooking was done on an open fireplace with roasting spits, and frying pans suspended by chains. (Reverend George Austen was on an income of circa 600 pounds per annum.) 

During the 1770s’, English kitchens were undergoing innovations. 
Jane Austen was aware of these such as the Rumford stoves. In NA, Catherine Morland was disappointed to find a Rumford at the Abbey and later in the ancient kitchen ‘stoves and hot closets of the present’.

By the time the Austen ladies moved to Chawton Cottage in the early 1800s’, Mrs Austen, Cassandra, Jane and Martha Lloyd were on an income of 500 pounds per annum (similar to the Dashwood ladies at Barton cottage in the 1790s’. S&S.) 

P.Hickman claims they certainly would have cooked on a range which by then had become standard in equipment in the homes of the gentry. 
So late 1770s’- early 1800s’ appear a transition time with kitchen ranges. Fuel costs and building renovation should probably be taken into account. I would say by the early 1800’s, an income of at least five hundred pounds would be required for a stove. 

Presumably, ovens became accessible to more people as the C19th progressed.