@ PelesTears- Prices of instantaneous water heaters vary, ranging from a couple hundred dollars for point of use systems installed at individual water use points to a couple thousand dollars for models that can heat up to eight gallons per minute. If you add a solar water heater, you can expect the price to double.
However, there are government rebates for energy efficiency improvements that will give you a tax credit for 30% of the purchase and installation price of these systems. You can also expect to cut your hot water bill in half. Manufacturers like Bosch also rate their systems service life at twenty years, and you can find refurbished units to purchase.
There are complaints that they can be finicky, so if you invest in one, be sure to take the time to tailor the settings to your water usage needs. This will save you from frustration down the road.