Tankless vs. tank is a conversion decision, not a like-for-like swap, and Denver's altitude and cold inlet water change the maths. This guide covers the differences that matter in Denver, and the published cost ranges with their sources. None of these figures are 5280 Denver Plumbing's prices.
How they differ
Tank: hot water on standby
A tank heater keeps 40 or 50 gallons hot all day and refills as you use it.
Tankless: hot water on demand
A tankless heater warms water as it flows through, so it never runs out, but its flow rate depends on how far the water temperature has to rise. In Denver that rise is large: January inlet water is cited at 43°F, and a February shower needs roughly a 70°F rise, so real-world gallons per minute land below the brochure figure.
Altitude matters
Denver sits at 5,280 feet. Gas appliances installed above 2,000 feet require high-altitude configuration under the fuel gas code, and installers cite a rule of thumb of about 4% derating per 1,000 feet above 2,000 feet. The exact derating for a given unit is a manufacturer matter. Electric and heat-pump water heaters are unaffected by altitude.
Efficiency
The U.S. Department of Energy framing, a national figure rather than a Denver measurement, is that tankless units are 24-34% more efficient than tank units for homes using 41 gallons or less of hot water a day, and 8-14% more efficient for higher-use homes. Hard water is the main tankless risk in Denver: scale is cited as the number one tankless killer, so descaling and maintenance matter more here than at sea level.
Published cost ranges
For a tank water heater installed, published ranges are $1,450-$2,400 from a published local guide, $1,850-$2,900 from a published local guide, $1,500-$3,800 in a local guide, and $1,300-$5,500 with most paying about $2,900 in a 2026 TradesProHub guide. For a tankless conversion, published ranges are $4,200-$6,800 from a published local guide and $3,500-$7,500 from a published local guide. Tankless conversion often needs gas-line upsizing, venting and a condensate drain, which is part of why it costs more. See tankless water heater installation and water heater installation.
| System | Published cost range | Best for |
|---|---|---|
| Tank water heater, installed | $1,450-$2,400 (a published local guide); $1,850-$2,900 (a published local guide); $1,500-$3,800 (local guide); $1,300-$5,500, most paying about $2,900 (TradesProHub 2026) | Lower upfront cost — a like-for-like swap where the existing setup suits a tank |
| Tankless water heater, conversion | $4,200-$6,800 (a published local guide); $3,500-$7,500 (a published local guide) | Endless hot water and higher efficiency — conversion often needs gas-line upsizing, venting and a condensate drain |
Permits
Replacing a water heater in Denver generally needs a permit, and the job is not considered complete until the work has been finaled. A replacement also needs an expansion tank on a closed system and code corrections where the existing install does not meet code. See water heater repair and repair or replacement: which is right for you.