Sterilising jam jars in the dishwasher is a good option if you have a large number to process.
Reusing jam jars keeps costs down and is much better for the environment than using new jars.
First off it's important to carefully check the jars for cracks or chips, don't be tempted to use these as they can be hiding places for bacteria.
Place the jars in the dishwasher and run through on a hot cycle, if the jars are already clean you can choose to leave out the soap, or just use half a tablet.
Jars will need to be dry and warm before filling with preserves, so may need to be put in the oven on a low setting. Put them upside down on a clean tea towel in a baking tray and set the oven to about 100 °C (212 °F).
Reusing lids is fine, make sure they have a plastic lining (most do if they have been used for food jars) and are undamaged, then clean them well in hot soapy water.
Sterilise by boiling in water for 10 minutes.
If using a jam funnel, sterilise this at the same time as the lids.
When ready to use the jars, take out of the oven and use a clean tea towel to turn the right way up. A good tip is to keep them in the baking tray while filling as this minimises mess from any spillages.