Bosch Tronic 6100 C 27
#10 in ElectricFull review
For a two bathroom home in a warm climate that wants a compact whole home heater with a 2 year parts warranty, double what Rheem gives.
Amazon $636.60$636.60
The Bosch Tronic 6100 C 27 is the better tankless water heater overall, rated 3.1 to 2.6. The Bosch Tronic 6100 C 27 leads on heating power and value. The Bosch Tronic 6100 C 18 wins on efficiency. The Bosch Tronic 6100 C 18 costs $51.14 less ($585.46 vs $636.60).
Bosch Tronic 6100 C 18
#16 in ElectricFull review
For a small home or apartment in a warm climate that wants the Bosch name. Most buyers get more power for the money elsewhere.
Amazon $585.46$585.46
Prices were last checked October 31, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Bosch Tronic 6100 C 27 for heating power (27 kW vs 18 kW) and value ($23.58 per kW ($636.60, 27 kW) vs $32.53 per kW ($585.46, 18 kW)).
- Choose the Bosch Tronic 6100 C 18 for efficiency (0.94 UEF vs 0.93 UEF).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every electric tankless water heater; a clear win is highlighted. How we rank explains each one.
| Factor weight | Bosch Tronic 6100 C 27 | Bosch Tronic 6100 C 18 |
|---|---|---|
| Overall rating | 3.1/5 | 2.6/5 |
| Value 35% | 49 $23.58 per kW ($636.60, 27 kW) | 25 $32.53 per kW ($585.46, 18 kW) |
| Heating power 25% | 64 27 kW | 28 18 kW |
| Efficiency 15% | 38 0.93 UEF | 50 0.94 UEF |
| Warranty 25% | 29 5-year heat exchanger warranty | 29 5-year heat exchanger warranty |
Specifications
| Bosch Tronic 6100 C 27 | Bosch Tronic 6100 C 18 | |
|---|---|---|
| Heating | ||
| Fuel | Electric | Electric |
| Electric power | 27 kW | 18 kW |
| Max flow | 5.3 GPM | 3.5 GPM |
| UEF | 0.93 | 0.94 |
| Installation | ||
| Voltage | 240 V | 240 V |
| Breakers | 120 A total | 90 A total |
| Weight | 14.8 lb | 14.8 lb |
| Features | ||
| Built-in recirculation | No | No |
| Wi-Fi | No | No |
| Heat exchanger warranty | 5 years | 5 years |
| Parts warranty | 2 years | 2 years |
| Released | 2023-01 | 2023-01 |