I have a vacation rental, anyone who has one knows that there is quite a bit of 'vacation waste' associated with the utilities.
In my area water for the first 3,000 gallons/month is reasonable but above that it is priced to encourage conservation. I have all the newer water conserving appliances: 1.6 gallon toilets, 2.5 gpm shower and front load washer. I averaged 3240/gal/mo last year. I installed two energy conservation devices with surprising results.
I have a larger walk in door less shower in the master bedroom. It's easy to take a long steamy shower.
I installed a toilet bag which displaces water in the tank. I played around with how full to fill the bag and still get a good flush. I also replaced the 2.5 gpm shower restrictor with a 2 gpm. A 2 gpm is still a decent shower, not one of those misting showers. Here are the products that I used:
https://www.amazon.com/Niagara-Conservation-Water-Saving-Toilet/dp/B003UQ5XAS/ref=sr_1_2?ie=UTF8&qid=1525203851&sr=8-2&keywords=toilet+water+saver and
https://www.amazon.com/LASCO-08-2483-Plastic-Thread-Restrictor/dp/B00HYWB9OS/ref=sr_1_3?ie=UTF8&qid=1525204162&sr=8-3&keywords=shower+restrictor&dpID=31VcCf0EKFL&preST=_SY300_QL70_&dpSrc=srchI expected a 3-400 gallons a month savings, instead it dropped to 2360/gal/mo, 880 gallons (27%) savings I attribute much of it to the shower restrictor. The one linked is a single hole restrictor, unlike the more common screen style. As the water rushes through that hole it vibrates creating a hum or whistle. You know the sound, you may have heard it in the last hotel you stayed at. I am sure that is not what the manufacturer intended but it has the replaced the pleasant sound of falling water to 'let me take my shower and get on with my day' sound .
If you have a vacation rental or even teenagers you might find this info useful.