Tankless Water Heaters
Updated February 24, 2026
Energy-efficient units that heat water on demand without storing it in a tank. Perfect for homes with limited space. Typical price range: $800-$2,500 for unit ($2,000-$5,000 installed for gas, $1,500-$4,500 for electric). Best for: homes that run out of hot water frequently, small spaces where a tank won't fit, and households willing to pay more upfront for long-term savings.
Overview
Tankless water heaters heat water on demand as it flows through the unit -- no storage tank. Turn on a hot water faucet and the heater fires instantly. Endless hot water as long as you are within the unit flow capacity. Gas-fired models (most powerful) handle whole-house demand. Electric models work for point-of-use (single fixture) applications. Energy savings of 20-35%% vs tank heaters because there is no standby heat loss. The tradeoff: higher upfront cost, potential for cold-water sandwich (brief cold burst between draws), and flow rate limitations during simultaneous multi-fixture use.
How to Choose Tankless Water Heaters
Tankless Water Heaters are best suited for homes that run out of hot water frequently, small spaces where a tank won't fit, and households willing to pay more upfront for long-term savings. They typically cost $800-$2,500 for unit ($2,000-$5,000 installed for gas, $1,500-$4,500 for electric), so plan your budget accordingly. Sizing is important — size by flow rate (gpm) and temperature rise. calculate: add up the gpm of all fixtures that may run simultaneously. the... Key advantages include unlimited hot water -- heats on demand, never runs out as long as you stay within flow capacity and 20-year lifespan -- nearly double a storage tank heater.
Pros & Cons
- Unlimited hot water -- heats on demand, never runs out as long as you stay within flow capacity
- 20-year lifespan -- nearly double a storage tank heater
- 20-35% energy savings vs tank heaters (no standby heat loss)
- Compact wall-mount saves floor space -- about the size of a suitcase
- No risk of tank rupture or catastrophic flood
- Higher upfront cost -- $800-$2,500 for unit, $2,000-$5,000 total installed (gas)
- Cold-water sandwich -- brief burst of cold water between back-to-back draws
- Flow rate limited -- running 3 showers simultaneously may exceed capacity
- Gas models need larger gas line and new venting ($200-$1,000 in infrastructure)
- Electric models may require 200-amp panel upgrade ($500-$2,000)
Key Features
- Heats water on demand -- no tank, no standby heat loss
- Endless hot water supply (within flow rate capacity)
- Compact wall-mount design saves floor space
- Gas models: 8-11 GPM flow rate, handles whole-house demand
- Electric models: 2-5 GPM, best for single fixtures or small apartments
Top Brands for Tankless Water Heaters
Sizing & Selection
Size by flow rate (GPM) and temperature rise. Calculate: add up the GPM of all fixtures that may run simultaneously. Then calculate the temperature rise needed (desired output temp minus incoming groundwater temp). In cold climates (40 degree F inlet water), you need more heating capacity than warm climates (70 degree F inlet). Gas: 8-11 GPM handles most homes. Electric whole-house: 4-8 GPM, may struggle with simultaneous fixtures in cold climates.
Installation
Gas tankless: requires a dedicated gas line (often larger than a tank heater), Category III stainless steel venting (not standard B-vent), and condensate drain. Electric tankless: requires a very heavy electrical circuit (100-150 amps for whole-house models). Both mount on a wall. Professional installation required. Gas tankless venting and gas line sizing are the most common installation challenges.
Maintenance
- Descale (flush with vinegar) annually in hard water areas. Scale buildup inside the heat exchanger reduces efficiency and can cause error codes.
- Clean the inlet water filter every 6-12 months.
- Check the venting annually for blockages or deterioration (gas models).
- Most units display error codes when service is needed -- consult the manual for your specific model.
- Tankless heaters last 15-20 years with proper maintenance -- significantly longer than tank heaters.
Buying Tips
- Rinnai, Navien, and Noritz are the three top residential gas tankless brands. All are excellent.
- Gas tankless is the only practical whole-house option. Electric tankless works for point-of-use only in most climates.
- A recirculation pump (-300) eliminates the wait for hot water and solves the cold-water sandwich issue.
- Budget ,500-3,500 installed for gas whole-house. The energy savings (-200/year) plus the longer lifespan (15-20 years) offset the higher upfront cost.
- If you have hard water, a whole-house water softener or descaling system is strongly recommended to protect the tankless heat exchanger.
Frequently Asked Questions
What are the advantages of tankless water heaters?
Unlimited hot water -- heats on demand, never runs out as long as you stay within flow capacity 20-year lifespan -- nearly double a storage tank heater 20-35% energy savings vs tank heaters (no standby heat loss) Compact wall-mount saves floor space -- about the size of a suitcase No risk of tank rupture or catastrophic flood
What are the disadvantages of tankless water heaters?
Higher upfront cost -- $800-$2,500 for unit, $2,000-$5,000 total installed (gas) Cold-water sandwich -- brief burst of cold water between back-to-back draws Flow rate limited -- running 3 showers simultaneously may exceed capacity Gas models need larger gas line and new venting ($200-$1,000 in infrastructure) Electric models may require 200-amp panel upgrade ($500-$2,000)
Who should buy tankless water heaters?
Tankless Water Heaters are best for: homes that run out of hot water frequently, small spaces where a tank won't fit, and households willing to pay more upfront for long-term savings.
How are tankless water heaters installed?
Gas tankless: requires a dedicated gas line (often larger than a tank heater), Category III stainless steel venting (not standard B-vent), and condensate drain. Electric tankless: requires a very heavy electrical circuit (100-150 amps for whole-house models). Both mount on a wall. Professional installation required. Gas tankless venting and gas line sizing are the most common installation challenges.
How do I choose the right size for tankless water heaters?
Size by flow rate (GPM) and temperature rise. Calculate: add up the GPM of all fixtures that may run simultaneously. Then calculate the temperature rise needed (desired output temp minus incoming groundwater temp). In cold climates (40 degree F inlet water), you need more heating capacity than warm climates (70 degree F inlet). Gas: 8-11 GPM handles most homes. Electric whole-house: 4-8 GPM, may struggle with simultaneous fixtures in cold climates.
What are the best brands for tankless water heaters?
Top brands for tankless water heaters include AO Smith, Bosch, Bradford White, Ecosmart. Each offers different price tiers and product lines.
How do I maintain tankless water heaters?
Key maintenance tips: Descale (flush with vinegar) annually in hard water areas. Scale buildup inside the heat exchanger reduces efficiency and can cause error codes.. Clean the inlet water filter every 6-12 months.. Check the venting annually for blockages or deterioration (gas models)..