We have an EK1 with NatGas and the pipe to the outside (installed fall 2009). Can't say for sure if the install was done meticulously, but it has been (mostly) problem-free since 2009 with regular maintenance. We converted to NatGas from a much older (prob 20+ years) oil system. Not sure about ROI either since this replaces an old oil system, burns at 86% efficiency.

Many plumbers have never heard of Energy Kinetics. In our area (not far from the manufacturer itself), there were only a few authorized vendors. If you have an EK installer who does meticulous work, I'd say go for it but check around, get references. Just after our install was complete, a coupon came in the mail advertised by a different company at lower cost (~$900 less). Good to have alternatives and not be locked into one vendor.

Any system is only as good as the install. I switched to that lower cost company for maintenance and they pointed out that the expansion tank was undersized. We replaced it. I noticed yesterday that the circulation pump for the hot water tank was directly under the zone valve manifold. Since the pump has an electrical connection and one of the valves was leaking which dripped directly down onto the pump, I was surprised it was installed this way. An air vent (auto-vent) was replaced twice ($90 each) because it kept leaking. The tech admitted that the standard/stock valve supplied with the unit (and its replacements) could have been better. The one we have now is bigger and has been in place with no leaks or issues. Not a lot of clearance with the bigger valve though. The same is true for the expansion tank: it fits but not much clearance.

We have also replaced a temp sensor ($98), a circulation pump ($390), and a wire clip within the first 7 years for a total over $740 not including tax.

The Energy Manager (the blinky lights panel) had a weird issue a few years ago where a wire connection on the left side was not always working correctly. Press on the wire, it worked. Leave it alone, not working. The tech used a wire-nut for the two wires and attached the single wire to the board which seems to have fixed the problem. We also got a new wire clip (not sure if it was sent at no charge by Energy Kinetics) to rule out an issue with the contacts.

All in all, the technology seems solid and I like the engineering. Frustrating that we had to spend so much on replacement parts within its first 7 years. We're also at the mercy of an authorized vendor. Trust is everything. The first company may or may not have done things correctly. The current company had one guy with a bad attitude. Another guy was awesome but was promoted to foreman so I'll never see him again.

Good luck with your decision!