RESIDENTIAL WATER HEATING
For 20 years Liquid Solar has been designing & installing innovative/efficient residential water heating systems.
CHOOSING AN EFFICIENT WATER HEATER
Often, when plumbers are replacing existing water heaters on older homes they will recommend the least efficient, lowest cost water heaters. Many builders and architects will do the same thing on new homes.
1. NEW CONSTRUCTION/NEW BUILDINGS
When designing a new home there are generally fewer constraints and thus more options. Some general recommendations:
The amazing efficiency of a heat pump water heater is hard to beat. Especially if the house is all-electric. Often makes sense even if house has natural gas or propane.
If house has solar PV or is all-electric, Marathon electric water heaters are long-lasting well insulated tanks that are an alternative to heat pump water heaters.
If natural gas/propane is preferred, then a tankless (on-demand) water heater is the most efficient. If a high efficiency gas boiler for hydronic heating is being installed, a tank water heater (often called a “water-maker” or “indirect tank”) tied to boiler is a decent choice.
A solar hot water system can be great if demand is high, or if a heat pump water heater or solar electric do not make sense. Plus there is definitely a certain elegance in using the sun to “heat your tank of hot water” !!
An electric tankless water heater is a good choice if mechanical area space is limited; if usage and occupancy is intermittent; or the load/demand is small (e.g. an ADU).
If home will have intermittent periods of high demand but maximum efficiency is desired, then a combination system with a heat pump water heater and a booster (e.g. tankless electric or gas) for periods of high demand works well.
2. EXISTING HOMES/BUILDINGS
On existing homes there are a lot factors at play in determining good efficient options, including (but not limited to): cost, local availability, performance, space/sizing, reliability, and fuel type.
Click on the table below to identify your existing water heater (fuel & tank type); then it easier to determine the best efficiency upgrade.
Note that it is best to replace an old water heater before it fails to avoid an emergency install of low efficiency water heater
WATER HEATER COMPARISON CHART - CLICK IMAGE TO ENLARGE
EFFICIENT RESIDENTIAL WATER HEATERS - PROS & CONS
Heat Pump Water Heater
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Pros
Uses 75% less energy than an electric water heater and 85% less than a gas water heater
Reliable, proven technology
Available in 50, 65 and 80 gallon sizes
Very D-I-Y friendly
May qualify for federal tax credits. City of Bozeman offers $500 tax credit.
Stiebel brand (our preferred) only requires 15 amp breaker; others 30 amps.
Cons
Not a good choice in small closet or small space (need at least 50-100 square feet; unless ducted).
Not recommended for high hot water demand (although increasing storage volume/# tanks may work).
Older model were noisy; new ones much better (the new Rheem is only as 48 decibels).
Some plumbers will claim “they don’t work” (wrong) and will not want to install.
They are taller than a standard electric water heater of the same tank volume.
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Installed cost: $2,500 to $4,000+ (not including tax credits). DIY source from Lowes etc for $1,500+
Preferred brand: Steibel-Eltron Accelera series; Bradford White Aerotherm series are our current preferred. But all brands are constantly improving.
Other brands like AO Smith, LG, Rheem seem good too.
The most efficient type water heater.
Electric Tank + Solar PV
If adding solar PV to an existing home that already has a electric water heater
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Pros
Basic electric water heaters are low cost and >95% efficient.
Add enough solar PV to cover usage of water heater and eliminate water heating costs.
Cons
Uses 3-4 times as much energy as a heat pump water heater.
Slow hot water production in high-use situations.
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Installed cost by plumber is >$1500. Standard 50-gallon electric tank is $700 (not including install) (30 amp breaker) from Lowes etc.
A MUCH better electric tank is the Marathon (by Rheem): they are non- metallic (will never corrode!!!) and very well insulated: $1300 for a 50g and they have a “stubby” (low and wide) shown in pic above.
On-Demand (Tankless) Gas
The most efficient gas water heater if the high efficiency versions is chosen.
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Pros
High hot water production if sized properly.
Efficient: 80% to 95% (depending on model chosen).
No standby energy loss from a tank.
Compact
Reliable and proven.
Many plumbers will install.
Cons
Requires venting and gas lines (unlike electric)
If hard water requires annual maintenance or hard water treatment system.
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Rinnai and Navian are two of the best brands. Rheem is good too.
An installed high efficiency tankless may be $2,5000 to $4,000.
The lowest cost (82% efficent) are $800 online
95% efficient models start at >$1400
On-Demand (Tankless) Electric Water Heaters
The most compact water heaters. Recommended for new construction and retrofits. Rock solid.
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Pros
Very efficient (no storage of hot water).
Very compact.
Can satisfy very high hot water demand situations if sized properly.
Durable and long lasting if properly maintained (hard water is the concern)
D-I-Y friendly
Low unit cost (but need to consider electrical costs)
Cons
Not good where water is very hard (or requires water softeners).
Some plumbers will claim “they don’t last” (we disagree).
Larger ones have high amperage requirements.
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Unit cost $450 to $800 (size dependent); Installed cost is 2x that but depends on wiring costs.
Steibel-Eltron Tempra series (many sizes); also Bosch, Eco-Smart and Rheem.
Not stocked locally. Available on-line or we can supply.
Wall Mounted Compact Tank Style Water Heaters (electric)
Very common in Europe where they will put several in a house and close to each point-of-use. But can be used as whole-house water heater where demand is low, or as a backup where water is pre-heated by solar or by an A2W heat pump.
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Pros
Space efficient; 20 or 30 gallon tanks.
Wall-mounted; high on wall so they do not occupy floor space; connections are on bottom of water heater.
Only requires 15 amp breaker.
Easy to adjust dial for water temp from 80F (vacation mode) to 160F (so smaller tank has more capacity).
Cons
Slow recovery rate once hot water is used up (but still fine for small homes).
Most plumbers don’t know about them and not available locally.
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Unit cost: $600
The only company that brings these in from Europe is Stiebel-Eltron
PSH20 Plus is 20 gallons and the PSH30 Plus is 30 gallons.
We can supply. Or available online.
Solar Hot Water (a.k.a solar thermal or solar heating)
Durable work-horse of water heating world that we love in the right situation. Can provide 70% of annual hot water demand. Turns otherwise un-used rooftop solar heat into hot water!
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Pros
High hot water production.
Not net-metered or tied to utility grid; not subject to utility monitoring!
Reliable and long-lasting if well designed and installed.
Cons
Requires backup water heater for cloudiest days.
Installers hard to find (but can be D-I-Y friendly).
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Installed: $6,000 to $10,000 + ; DIY: $2,500 to $5,000 +
We are dealers for Sun Earth and we believe they make the solar collectors, racking, and an excellent app-based solar control
We source Stiebel Eltron tanks as we have found they are long lasting, affordable, and well insulated