Energy saving advice---
If you're doing your laundry correctly, bacteria shouldn't be a major concern. The type of bacteria that's likely to be found on your clothes do not survive normal washing, even at 40C. So, unless you or someone in your household has some kind of unusual skin infections you really do not need to worry too much about it. Just run a standard cotton wash with the correct dose of detergent for your water quality and the type of stains on the clothes. You clothes will be as hygenically cleaned as is necessary for normal use.
If you are cleaning items which are actually contaminated with bacteria, e.g. clothes that might have been in contact with raw meat, you can do a pre-wash with clear Detol disinfectant. However, DO NOT use the orange/brown 'traditional' variety of detol as it will stink your washing machine out for weeks and your clothes will smell like a hospital!
Kitchen clothes should really be soaked in a sink/bucket containing disinfectant before they're ever put into a washing machine.
Likewise, you can prewash towels with clear Detol should you wish to do so. Same goes for pet beds etc
To keep your machine healthy :
If you are running full-length cotton cycles at 40C or more and using good quality detergent, in general you won't have much of a problem, particularly in soft water areas.
Run a full length cotton cycle with a good standard detergent like Ariel or Persil (not-colour version) once in a while at 90C. Maybe once a month.
You can throw your kitchen clothes or other items that need to be sanitized into that cycle too to avoid wasting energy.
If you're in a hardwater area, use a water softener like calgon in each wash. There are also good alternatives from Tesco etc and even Lidl's water softener's pretty effective. These are not-phosphate based btw.
If you're in a hardwater area and your machine has become very gunked-up, you can get a washing machine descaler. It's available online. However, I've found Finish or Sun dishwasher cleaner equally effective.
Pour the cleaner straight into the drum and run a 90C cottons wash and turn on any enhancement options like "Aqua Plus" (Bosch) "Water Plus and Wash plus" (Miele) .. Superwash (hotpoint) etc..
The single biggest problem for washing machine gunking-up other than limescale tends to be fabric softener.
If you are using a lot of softener, you do need to run a hot wash now and then to clear it out. A good detergent should also be capable of washing away any softener gunk that's left in the drum, even at low temps.
Other tips:
Use the correct dose of detergent - over dosing leads to gunk build-up.
Use a good quality detergent and softener.
Avoid 2-in-one detergent/softener combinations as they leave residues.
Do not exclusively use the QuickWash option, this leaves a lot of residues behind! Many people do almost all of their washing on this option and then wonder why their machine gets disgusting inside!
In summary to save energy:
Reduce the temp from 60 to 40 in your colour washes
Try doing your whites at 40C but on a long white cotton cycle and put in a scoop of Vanish crystal white, (combination of oxygen bleacn + enzymes). Results are often better than a 90C wash!!
Use quickwash options where appropriate e.g. if you're just washing a very small load of lightly soiled items.
Do a monthly boil wash to keep you machine healthy!
