The whole-house Tronic 6100 C needs no gas line or vent. Its 27 kW model does need three 40-amp double-pole breakers, so we check your electrical service first.
Bosch’s electric tankless range splits by job: one family heats water for the whole house, the other for a single sink or fixture.
WHOLE-HOUSE ELECTRIC
Two models, 18 and 27 kW, rated 3.51 to 5.26 GPM at a 35°F rise. Both are built for 240 volts. Thermostatic modulation holds a set temperature from 86°F to 125°F, and an inlet water filter is built in.
GPM figures are Bosch’s ratings at a 35°F temperature rise. Breakers, wire size and voltage differ by model, so the heater in your quote sets the numbers.
Bosch water heaters in North America come from Bosch Home Comfort, a separate business from Bosch home appliances. Its US company, Bosch Thermotechnology Corp., is based in Watertown, Massachusetts, and is part of the Bosch Group, founded in Stuttgart, Germany, in 1886.
Bosch has sold tankless water heaters in the US since at least 2000: its warranty library still lists AquaStar gas models from that year. Bosch’s US catalog now offers heat pump, small storage, electric tankless and indirect storage water heaters, and it files its Greentherm, Therm and AquaStar gas tankless lines under discontinued products. A new Bosch tankless today means one of two electric families: the whole-house Tronic 6100 C or the point-of-use Tronic 4000 C.
Bosch gives the 6100 C 3/4-inch NPT fittings on both the cold and hot water connections, which it says allow high flow and easy tank replacement, plus a built-in inlet water filter. Because it heats with electric elements, a swap also needs no gas line or condensate drain, and in Bosch’s words, “there is no venting.”
The 6100 C uses what Bosch calls thermostatic modulation to hold a constant output temperature. You choose that temperature, from 86°F to 125°F, with buttons on the front of the heater.
Start with the job. The 6100 C is Bosch’s whole-house tankless, built to take over from a main water heater. The 4000 C serves one point of use and is small enough to fit under a sink.
For a whole house, size by flow and temperature rise together, because the flow a tankless delivers falls as the rise grows. Bosch rates the TR6100C-27 at 5.26 GPM for a 35°F rise, 4.09 GPM for 45°F and 2.39 GPM for 77°F; the TR6100C-18 gives 3.51 GPM at 35°F. Incoming water in Houston averages about 67°F, and the seasons shift it, so the rise you need changes during the year.
Then check the supply. Both 6100 C models are built for 240 volts and still run at 208 volts, but heat less: the TR6100C-27 drops from 27 kW to 20 kW.
Last, recirculation. Bosch approves both families for unheated water only, which takes a recirculation loop off the table and means the 4000 C cannot boost hot water from another heater. For faster hot water at a distant tap, Bosch points to an electric mini-tank such as its Tronic 3000T, installed inline near the fixture.
Bosch states that the Tronic 6100 C “includes a 5-year limited warranty,” and its product pages go no further than that headline. The full terms sit in a single limited warranty document for the Tronic 4000 C and 6100 C series, listed in Bosch’s water heater warranty library, so read it before you count on a specific parts or labor term. Bosch’s 6100 C manual adds that failures caused by lime scale build-up are not covered.
With no gas line or vent to run, the electrical supply sets the scope. The TR6100C-27 needs three dedicated 40-amp double-pole breakers and three sets of 8 AWG wire plus a ground, and draws up to 112.5 amps at 240 volts. The TR6100C-18 needs three 30-amp double-pole breakers on 10 AWG wire and draws up to 75 amps. Both are hard-wired only, and Bosch’s electric water heater FAQ cites NEC 422.31 for a local disconnect when the panel is out of sight. Swapping an older Bosch WH17, RP17 or AE-115 for a TR6100C-18 means rewiring, because those models used two 40-amp breakers. Before we quote, we check that your electrical service can carry the load.
Bosch sets plumbing and location rules too. The water connections must face down toward the floor, and on the 6100 C all piping within 3 feet of the heater must be rated for at least 185°F. Choose an indoor room that stays between 32°F and 104°F, and leave out the attic: Bosch warns attic temperatures may often exceed 104°F.
In Texas the plumbing permit is the job of the Responsible Master Plumber, a licensed master plumber, and inside Houston that plumber also has to be registered with the City. For a Tronic, plan around our published tankless range of $4,200 to $8,000, which covers the heater and the installation; our tankless installation page lays out what pushes a job toward either end. Where an existing tankless already has the right circuits, swapping in a new Tronic typically takes 4 to 6 hours. Replacing a tank? Our tank-to-tankless planning guide and Houston permit guide cover the steps.
Bosch’s product pages say the Tronic needs “virtually no maintenance,” yet its maintenance guide sets out a routine. Owners should check daily for leaks around the heater. Once a year, a qualified service person should clean the inlet filter screen, test the heating elements and clean off any limescale, and the heater should never run without its filter screen.
The 6100 C manual adds a flush once a year, or every six months where the water is unusually hard. It warns that water with a mineral concentration over 250 mg/L may cause scale that can damage the heater, and it recommends an anti-scale treatment for hard water. The City of Houston’s 2025 report puts its main system average at about 8 grains per gallon, or 135.5 ppm: under Bosch’s figure, though the USGS classes it as hard. We recommend that yearly flush and can add whole-house filtration and softening if you want treatment as well. Our tankless maintenance visit is a yearly flush at $195 flat, with a professional descale, our 12-point check and a written report you keep. If your Tronic stops delivering hot water, our tankless repair technicians pin down the fault first; most tankless repairs come to $150 to $600.
If you own a Greentherm, Therm or AquaStar gas tankless, Bosch now files it under discontinued products. Bosch’s Greentherm 9000 page lists a 15-year heat exchanger warranty and a 5-year limited warranty on parts, and the warranty library still keeps documents for discontinued models. We can assess an older unit and plan a repair or a replacement. A new Bosch would mean going electric; a gas tankless from another brand is the other route, and our brand guides compare them.
Hot Water Guys installs, repairs and maintains Bosch electric tankless water heaters across Greater Houston. A Tronic plan starts with your electrical service, then an indoor spot and the hot water you use at once.
The 6100 C heats water for a whole house; the 4000 C serves one sink or fixture. We size either one by the flow you use at once and the temperature rise.
Built for 240 volts, the TR6100C-27 needs three 40-amp double-pole breakers and 8 AWG wire, and draws up to 112.5 amps. Your service has to carry that.
Both families install indoors only, in a room that stays between 32°F and 104°F. Bosch warns attics may often run hotter. There is no vent to route.
Both families are approved for unheated water only. That rules out recirculation, and it means the 4000 C can’t act as a booster for another heater.
Neither Tronic family goes outdoors. Bosch certifies the 6100 C for indoor installation only and offers no outdoor version, and its manual says to keep the heater and its water piping away from freezing temperatures.
Bosch calls the Tronic virtually maintenance-free, yet the 6100 C manual asks for a yearly flush, or one every six months in unusually hard water.
Bosch’s guide asks a qualified service person, once a year, to take out and clean the inlet filter screen, check the heating elements’ resistance and remove any scale.
Bosch’s 6100 C manual warns that water above 250 mg/L of minerals may cause damaging scale. Houston’s water averages about 8 grains per gallon (135.5 ppm), hard to the USGS but below that figure.
Bosch states a 5-year limited warranty for the Tronic 6100 C. Its warranty library holds one limited warranty document for both Tronic families, with the full terms.
Older Bosch gas units have their own documents in the same library. Bosch’s Greentherm 9000 page lists 15 years of heat exchanger coverage and a 5-year limited parts warranty.
What to know before a Tronic goes in, and what to do with an older Bosch gas unit.
Choose the 6100 C to replace your main water heater: it is Bosch’s whole-house model, in 18 and 27 kW versions. Choose the 4000 C for one sink or fixture; its four models range from 0.59 GPM (TR4000C-3) to 2.04 GPM (TR4000C-10) at a 35°F rise.
At a 35°F temperature rise, Bosch rates the TR6100C-27 at 5.26 GPM, and at a 45°F rise, 4.09 GPM. On an average day Houston’s incoming water is about 67°F, so a 45°F rise lifts it to about 112°F. Winter water arrives colder and needs a bigger rise, which cuts the flow, so we size for the colder months and the fixtures you run at once.
The TR6100C-27 is built for 240 volts and needs three 40-amp double-pole breakers, the TR6100C-18 three 30-amp breakers. The 4000 C ranges from one 30-amp breaker at 120 volts to one 50-amp breaker at 240 volts. Neither goes outside: the 6100 C is certified for indoor installation only, and both families need a room between 32°F and 104°F.
Not in the US. Bosch has discontinued its Greentherm, Therm and AquaStar gas models, and every tankless it sells here today is electric. If you own one of those gas units, we can assess it and plan a repair or a replacement, whether that is an electric Bosch or another brand’s gas model.
The 6100 C manual says to flush the unit yearly, or twice a year where the water is unusually hard. Bosch’s maintenance guide adds a yearly visit to clean the inlet filter screen and test the heating elements. With Houston’s water at about 8 grains per gallon, hard on the USGS scale, we recommend keeping that yearly appointment.
Our published range for a tankless heater and its installation is $4,200 to $8,000. Where a Tronic job lands in it depends on the model, the breakers and wiring it needs, your panel’s spare capacity and any code work. The range is general, not a price for a particular model, so call 832-673-0909 for a free quote.
Bosch says the Tronic 6100 C comes with a 5-year limited warranty. For anything beyond that headline, such as parts or labor terms, read the limited warranty document for the Tronic series in Bosch’s warranty library; it covers both families. Older Bosch gas models have documents there too.
Running an older Bosch gas unit, or ready to go electric? Tell us what you have now, and we’ll plan the repair, replacement or new Tronic.