Instruction: Analyze a question and its supporting document. Predicting answerability based on the information provided in the document. Output yes if the document contains relevant information to answer the question, otherwise output no.

Input:
Question: does this heater use propane gas?
Document: Install somewhat involved because wanted to hide pipes in wall. Tank water heaters have gas line down low and water lines up high. I moved them to same elevation under Eccotemp for a clean looking install. This tankless water heater is for 1 or 2 peeps only that realize if someone is in the shower do not use the hot water. Should work great for anyone living solo. I have had to reset 2 times by unplugging the power cord. That happened first two days and has not happened sense.
When you get to plumbing the water lines, you do need to purchase the service valves, they are not included. If you live in an area that requires a back flow preventer check valve you will have to purchase that as well. For plumbing the gas, you need to purchase a gas shut off valve, a section of flex gas line and the appropriate piping/fittings for your needs. Use white or pink thread tape for your brass water fittings and yellow gas tape or pipe dope for your gas fittings.
Turn on the hot water and adjust until you get the right temp. I had my previous water heater on low so when the hot only is on, it is slightly higher than I like for shower temperature so I can add a little cold to suit.I adjusted my new heater in the same way. The left control barely on (Gas Volume Regulator) adjusts the temperature.
The Eccotemp FVI-12-NG High Capacity Gas Tankless Water Heater did not have enough water flow for the bathtub. The 1/2 inch inlet and outlets are just not big enough. I recoommend the 40NI at a minimum as it has 3/4 inch inlet. It is rated at 6+ gpm instead of 3.5 gpm. Not sure why they call it High Capacity and say it is a good unit for a 1 bath house.
It is around $600.00. When I saw the Eccotemp FVI-12-NG Direct Vent Natural Gas Tankless Water Heater for about half the price, I checked it out.I was worried if it would fit my usage needs because it produced less hot water. I read the reviews and went ahead and order it from Air and Water. I put in the on a Tuesday and I got it on Friday in time for me to install it on the weekend.
This small unit was perfect for my two bedroom one bath house. The issue is this; if you have single handle faucets, when tempering the hot water the blend valve reduces hot water flow while introducing cold water to the stream. The water heater senses the reduction in flow and shuts off, giving the bather a dose of cold water. Using the controls on the water heater to reduce gas flow and temperature setting allows the user to set the hot water temperature to about 110 degrees.
My water is metered and this POS is going to cost me. I turn the shower hot about as high as it will go and then it barely lights this heater and then if anything slightly drops the pressure as in cold water turned on somewhere then the flow to unit drops slightly and it turns off.Update:  6/18/14  After a couple months use (few times of messing with it for a fifteen minutes each) I finaly got it dialed such that it works sort of OK.
After getting the exhaust pipe and an adapter (on-line), the rest of the installation wasn't terribly difficult. Since the unit was so cheap and I believe in being cautious, I left the old, completely functional electric tank hot water heater in place but valved off.The Eccotemp worked 'okay' for a year - - including a normally cold winter with many below zero periods. The biggest in-use issue was that the temperature in my daughter's shower was adjustable onle at the heater, itself.
It is about the size of a standard suitcase.I made a list of plumbing parts to hook it up and went to Home Depot. I needed adapters and  inch and  inch pipes and a pressure relief valve. I used a standard 60 inch Dryer Flexible hose to connect the gas.
I suspect thats because of the energy star issue as well. I'm not complaining though, they offset that with a great price point. It has been a solid running efficiant unit, I'm just sharing what I have found so you can be a wise consumer.I cant speak of gas savings at this point as we are heading into winter and my furnace is on as well. I will try to update in the summer when the furnace is off.
Answer: yes