Giant GTHPCO-45 1+GTXST-66 1
Covers every color and finish of this model.
ENERGY STAR certified
Heat pump water heater · 60 gallons
Inthis water heater costs
about $20 a month
$242 a year
An estimate at your state's average rate — not a guarantee of your bill.
The yellow sticker says $188 a year.
You'll pay $54 more.
Sticker uses 14¢ per kWh. The U.S. average is 18.0¢ per kWh.
Energy use
1,341 kWh a year
vs similar heat pump water heater
+19%
Cheaper water heaters, same size
ENERGY STAR lists 17 other certified models at the same 1,341 kWh a year, size and type, so everything on this page applies to them too.
- A. O. Smith HPACO-45 1+AXST-66 1
- A. O. Smith HPACO-45 1+AXST-66TTP 1
- A. O. Smith HPACO-45C 1+AXST-66C 1
- A. O. Smith HPACO-45C 1+AXST-66CTTP 1
- American MHPCO-45 1+MXST-66 1
Cheaper to run, same size
- Smart Solar SSG2-ES 65Heat pump water heater · 65 gallons$161
- Friedrich PROH65 T2 FD310BMHeat pump water heater · 59 gallons$162
- Friedrich PROH65 T2 FD310UMHeat pump water heater · 59 gallons$162
- Friedrich PROH65 T2 FD350BMHeat pump water heater · 59 gallons$162
A year at the U.S. average residential rate.
Cost in every state
1,341 kWh a year × each state's average residential rate (EIA 12-month average through July 2026).
| State | Rate | Per year | Per month |
|---|---|---|---|
| Hawaii | 43.7¢ | $586 | about $49 a month |
| California | 33.1¢ | $444 | about $37 a month |
| Massachusetts | 30.4¢ | $408 | about $34 a month |
| Rhode Island | 29.4¢ | $394 | about $33 a month |
| Maine | 29.3¢ | $393 | about $33 a month |
| New York | 28.4¢ | $380 | about $32 a month |
| Connecticut | 28.2¢ | $378 | about $32 a month |
| Alaska | 27.0¢ | $362 | about $30 a month |
| New Hampshire | 26.8¢ | $359 | about $30 a month |
| District of Columbia | 24.2¢ | $325 | about $27 a month |
Show all 52 statesShow fewer
| Vermont | 23.9¢ | $320 | about $27 a month |
|---|---|---|---|
| New Jersey | 23.6¢ | $317 | about $26 a month |
| Maryland | 22.3¢ | $299 | about $25 a month |
| Michigan | 21.0¢ | $282 | about $23 a month |
| Pennsylvania | 20.8¢ | $278 | about $23 a month |
| Illinois | 19.0¢ | $255 | about $21 a month |
| Wisconsin | 18.8¢ | $252 | about $21 a month |
| Ohio | 18.3¢ | $245 | about $20 a month |
| U.S. average | 18.0¢ | $242 | about $20 a month |
| Delaware | 18.0¢ | $241 | about $20 a month |
| Indiana | 17.1¢ | $229 | about $19 a month |
| Virginia | 16.6¢ | $222 | about $19 a month |
| Colorado | 16.6¢ | $222 | about $18 a month |
| Alabama | 16.5¢ | $221 | about $18 a month |
| Minnesota | 16.2¢ | $218 | about $18 a month |
| Texas | 16.0¢ | $215 | about $18 a month |
| South Carolina | 15.7¢ | $211 | about $18 a month |
| West Virginia | 15.7¢ | $210 | about $18 a month |
| Oregon | 15.6¢ | $209 | about $17 a month |
| Arizona | 15.5¢ | $207 | about $17 a month |
| Florida | 15.4¢ | $207 | about $17 a month |
| New Mexico | 15.2¢ | $204 | about $17 a month |
| Kansas | 15.1¢ | $203 | about $17 a month |
| Georgia | 15.1¢ | $202 | about $17 a month |
| Mississippi | 14.9¢ | $200 | about $17 a month |
| North Carolina | 14.9¢ | $199 | about $17 a month |
| South Dakota | 14.3¢ | $191 | about $16 a month |
| Washington | 14.2¢ | $190 | about $16 a month |
| Wyoming | 14.2¢ | $190 | about $16 a month |
| Iowa | 14.1¢ | $189 | about $16 a month |
| Kentucky | 14.0¢ | $188 | about $16 a month |
| Montana | 13.9¢ | $187 | about $16 a month |
| Missouri | 13.9¢ | $186 | about $16 a month |
| Tennessee | 13.7¢ | $183 | about $15 a month |
| Oklahoma | 13.6¢ | $183 | about $15 a month |
| Nevada | 13.6¢ | $182 | about $15 a month |
| Arkansas | 13.5¢ | $180 | about $15 a month |
| Utah | 13.3¢ | $178 | about $15 a month |
| Louisiana | 13.1¢ | $175 | about $15 a month |
| Nebraska | 12.9¢ | $173 | about $14 a month |
| Idaho | 12.7¢ | $170 | about $14 a month |
| North Dakota | 12.5¢ | $168 | about $14 a month |
What the Giant GTHPCO-45 1+GTXST-66 1 costs where electricity is expensive
At Hawaii's average residential rate of 43.7¢ per kWh, the Giant GTHPCO-45 1+GTXST-66 1 costs $586 a year — $398 more a year than the label says. The EnergyGuide label estimates $188 a year, because every label in the country is calculated at 14¢ per kWh. At the U.S. average of 18.0¢ per kWh this water heater costs $242 a year, and in North Dakota, the cheapest state, $168 a year.
| Where | Rate | Cost a year | vs the label |
|---|---|---|---|
| Hawaii | 43.7¢ per kWh | $586 | +$398 |
| California | 33.1¢ per kWh | $444 | +$257 |
| Massachusetts | 30.4¢ per kWh | $408 | +$220 |
| Rhode Island | 29.4¢ per kWh | $394 | +$206 |
| Maine | 29.3¢ per kWh | $393 | +$205 |
| North Dakota | 12.5¢ per kWh | $168 | −$20 |
Electricity prices: EIA 12-month average through July 2026, residential sector, average revenue per kWh. Label figure calculated at 14¢ per kWh, the rate the FTC requires on labels.
Full specs
At the U.S. average residential rate this one costs $242 a year — about 19% more expensive to run than the average heat pump water heater ($203 a year across 510 certified models).
Every model on this scale is ENERGY STAR certified. Range across 510 heat pump water heaters, priced a year at the U.S. average residential rate.
- Brand
- Giant
- Model number
- GTHPCO-45 1**+GTXST-66 1**as ENERGY STAR lists it; * and # stand for color and finish codes
- Model name
- Split System Heat Pump
- Type
- Heat pump water heater
- Capacity
- 60 gallons
- Annual energy use
- 1,341 kWh a year
- Combined Energy Factor (CEF)
- 3.7
- ENERGY STAR Most Efficient
- No
- On the market since
- February 2026
- Certified
- March 2026
- Tank volume (gallons)
- 60
- First-hour rating (gallons)
- 82
- Uniform Energy Factor (UEF)
- 3.70
- Draw pattern
- High-Usage
- Heat pump type
- Split System HPWH
- Recovery efficiency (%)
- 435.00
- Tank height (in)
- 59
- Tank diameter (in)
- 18
Where to buy
We do not sell appliances. These open a search on the retailer's own site.
Common questions
+How much does the Giant GTHPCO-45 1+GTXST-66 1 cost to run per month?
about $20 a month at the U.S. average residential rate of 18.0¢ per kWh, or $242 a year. Your cost depends on your state's rate — see the table above.
+How many kWh does the Giant GTHPCO-45 1+GTXST-66 1 use?
1,341 kWh a year, as the manufacturer filed it with the EPA, in the ENERGY STAR certified product database.
+Is the Giant GTHPCO-45 1+GTXST-66 1 energy efficient?
It is listed as ENERGY STAR certified. It uses about 19% more electricity than the average heat pump water heater (average: 1,123 kWh a year).
+How does the Giant GTHPCO-45 1+GTXST-66 1 compare to the average water heater?
The average heat pump water heater in our database uses 1,123 kWh a year, costing $203 a year at the U.S. average residential rate. The Giant GTHPCO-45 1+GTXST-66 1 uses 1,341 kWh a year, costing $242 a year.
How we calculate this
Annual energy use (1,341 kWh a year) is the figure the manufacturer filed for this model with the EPA, in the ENERGY STAR certified product database. Running cost is that figure multiplied by a state's average residential electricity price from the U.S. Energy Information Administration (12-month average through July 2026, average revenue per kWh).
The annual figure for a water heater assumes a hot water draw of 10, 38, 55 or 84 gallons a day, set by the heater's first-hour rating, per the DOE test procedure (10 CFR 430 Subpart B, Appendix E). Full methodology.
Sources: EPA ENERGY STAR certified product data, updated weekly · U.S. EIA electricity prices, 12-month average through July 2026.