I recently became the tech person for some friends who are selling older generation HPWH. There are Nyletherms and E-techs which are both about ten years old. The website is heatingstuffllc.com. The units on the website are new old stock. You can email me if you have questions. There are about 1200 units that are used and are being sold for a bit more than scrap. I am starting to test some of them. Some are fine, some leak water from the double walled heat exchanger. I think the leakers are usable with an unpressurized tank with some JB weld to seal the vent leak on the hx. I will be testing this over the next couple weeks. The used units are $100. These make the use of a HPWH a great choice for solar back up or wood boiler back up in the summer for DHW.