How can I tell if I have enough natural gas available to run a tankless hot water heater. I already have two furnaces and a gas dryer. What would happen if my demand exceeds my supply?

it has an electric pilot?

I inherited this house when my Father passed. When I started poking around I noticed I could not find the water heater. Anywhere! Now, there is a large unit of some kind in the attic. It looks to be fairly new. It's not the central units, they are both outside. While watching a home remodeling show on TV I noticed this unit being installed, a tankless water heater. It looks almost exactly like what's in my attic. I didn't go as far as climbing around in the attic to see if it had any labels on it, the attic is very small and it's pretty hard to get to. But since I seem to have no blessed water heater, is it a good bet I have a tankless in my attic?
I have central heat and air.

It's detailed as 4kw and 110v - these are all the specs available to me.
Am I correct in thinking this will pull 4000w? (That's huge!!).
Considering it will only be used for short showers by me a few times a week, can I get away with a less robust step down transformer?

at present the heater is disconnected as I had a water leak in the main line and would like to clean it before I have it hooked back up. It is a Rheem, manufactured in 1982 and is a 30 gal. Thank you for any help you can give me. Joanne

Residential Construction.

I was told that the electric variety of tankless water heaters suck up a lot more juice than their propane/nat gas counterparts. The reason I am considering electric is that I don't want an extensive installation - I just want to replace my old electric tank heater with a wall-mounted tankless one. Is it worth it?

Thinking of changing our water heater from conventional one to a tankless unit. We are in California. What should we expect to pay for installation of a tankless water heater?

my gas water heater needs to be replaced ASAP. Can anyone reccomend a good electric 40 gal tank or a electric tankless water heater for a mobile home with two adults and one child.......hopefully under 0?

It would be for the whole house...2.5 baths, dishwasher, washer, 4 people.

I have forced hot water now and oil heat. I am replacing an oil inner coil now.

And where can you buy it? Why is it the best and how do you know it is the best.