Installing tankless water heater need a professional touch. You can not do it yourself because this is different things to do. Except you are an expert on this industry, I am really recommended you to get pro service.
To run it well in house, you should install the device properly. They are also need some supplies that not come inside the box when you purchase the product. You can check the top products on best tankless water heater reviews.
Budget for install and supplies is different from some place to another. The expert have some consideration when calculating it. But it short, you should have budget about $300 to $800 for standard installation and supplies.
You can also get 2 different things like electric or gas tankless water heater reviews. Be sure to check the compability with your house before deciding to pick it up and install it on your house.