Tankless Water Heaters Frequently Asked Questions
- Gas vs. electric?
- What is the payback?
- What are the disadvantages of tankless water heaters?
- Can I put the unit outdoors?
- How many have you installed?
- How long does the installation take?
- How far away from your office do you install?
- Recirculation systems, instant hot water and hot water delay times?
Gas vs. electric?
To us, this has a simple answer. Natural gas has 28.5 kWh per therm (100,000 btu).
At $0.15 per kWh and $1.10 per therm annual average, this makes electric water heating (be it tank or tankless) around Oakland CA three times more expensive than gas.
Also, to get the capacity of a modern tankless (over 150,000 btu/hr output heating capacity) would require around 42 kW around 160 amps! Older homes have electrical service entrance capacities of 100 amps, newer ones 200 amps. Except for the occasional office building sink, in which case a small electric heater can be used, natural gas, or even propane, is the way to go. Another exception is for homes with photovoltaic systems and excess production. In that case an electric tank heater is recommended.
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What is the payback?
Payback is the amount of time for the unit to pay for itself. Paybacks on tankless heaters usually average 5-6 years. Please see: spreadsheets tankless.savings.calculator.xlsx. The net present value of a tankless heater, given its 20-40 year life, is very high.
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What are the disadvantages of tankless water heaters?
Higher initial cost is probably one of the biggest disadvantages, but when you think of that you are pre-paying 40% of your hot water gas bill for the next 30 years, the cost is well worth it. Also, tankless water heater are not good for homes with anemic hot water pressure, because, at full flow rates, they drop around 10 psi on the hot circuit. With most modern homes, there is no problem.
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Can I put the unit outdoors?
Absolutely. Outdoor installations lower the cost because the need for stainless fluing parts are eliminated. We recommend the Noritz for all of our outdoor installations because it has a gasketed cover and comes in a special outdoor version.
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How many have you installed?
Tanknot Tankless – David Shevick, P.E. and his team – has installed over 800 tankless water heaters in the Bay Area. We have an extremely high client satisfaction rate.
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How long does an installation take?
Typical installations are done in 7-9 hours.
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How far away from your office do you install?
Tanknot Tankless installs throughout Northern California.
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Recirculation systems, instant hot water and hot water delay times?
Tankless water heaters add a 5 second delay in hot water delivery time compared to the existing delay of the tank water heater. This is due to their ignition time. Hot water delay is almost exclusively a function of the pipe length from the water heater (tank or tankless) to the fixture being used. Some systems use a Recirculation Return System to keep water always hot at the fixture. These are entirely compatible with tankless water heaters. In fact, the Noritz tankless water heaters have a built-in controller for recirculation pumps which only turns the pump on when needed. In applications when there is no recirculation return system (which require a return pipe from the fixture areas back to the water heater) there are Instant Hot Water devices designed to fit under a sink which quickly bring hot water to the fixture by shunting the hot and cold circuits and pumping water in the hot water line which has gone cold back into the cold line in a loop until hot has arrived. This avoids wasting hot water.
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