ThermoMate CZ750NG
#6 in GasFull review
A low cost indoor whole home heater for natural gas homes, but check the warranty with ThermoMate before buying.
Amazon $739.99$739.99
The ThermoMate CZ750NG is the better tankless water heater overall, rated 4.1 to 3.4. The ThermoMate CZ750NG leads on value and heating power. The ThermoMate RTC68iN wins on efficiency. The ThermoMate CZ750NG costs $360 less ($739.99 vs $1,099.99).
ThermoMate RTC68iN
#15 in GasFull review
A budget condensing heater for natural gas homes that want PVC venting and lower gas bills, if you can live with an unclear warranty.
ThermoMate $1,099.99$1,099.99
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 ThermoMate CZ750NG for value ($3.72 per 1,000 BTU/h ($739.99, 199,000 BTU/h) vs $6.75 per 1,000 BTU/h ($1,099.99, 163,000 BTU/h)) and heating power (199,000 BTU/h vs 163,000 BTU/h).
- Choose the ThermoMate RTC68iN for efficiency (0.91 UEF vs 0.81 UEF).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every gas tankless water heater; a clear win is highlighted. How we rank explains each one.
| Factor weight | ThermoMate CZ750NG | ThermoMate RTC68iN |
|---|---|---|
| Overall rating | 4.1/5 | 3.4/5 |
| Value 35% | 100 $3.72 per 1,000 BTU/h ($739.99, 199,000 BTU/h) | 52 $6.75 per 1,000 BTU/h ($1,099.99, 163,000 BTU/h) |
| Heating power 25% | 100 199,000 BTU/h | 54 163,000 BTU/h |
| Efficiency 15% | 6 0.81 UEF | 69 0.91 UEF |
| Warranty 25% | 50 heat exchanger warranty not published (neutral score used) | 50 heat exchanger warranty not published (neutral score used) |
Specifications
| ThermoMate CZ750NG | ThermoMate RTC68iN | |
|---|---|---|
| Heating | ||
| Fuel | Gas | Gas |
| Gas type | Natural gas | Natural gas |
| Gas input | 199,000 BTU/h | 163,000 BTU/h |
| Max flow | 8 GPM | 9.4 GPM |
| UEF | 0.81 | 0.91 |
| Condensing | No | Yes |
| Installation | ||
| Venting | Indoor | Indoor |
| Vent type | 3 in OD vent | PVC |
| Weight | - | 50 lb |
| Features | ||
| Built-in recirculation | No | No |
| Wi-Fi | No | No |