Hybrid Electric Pump Water Heater in Northern Climate?

Post by talzara » Sat Sep 18, 6:49 pm

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dratkinson wrote: '

Sat Sep 18, 4:13 pm

I remembered this from a HS physics class. Energy can be transformed from one type to another (mechanical, electrical, chemical, heat,...). But every transformation results in a net loss of total energy. A heat pump WH inserts a mechanical transformation, for what was direct NG consumption.

...

I could be wrong, but am blind to any flaws in my logic.

I remembered this from a HS physics class. Energy can be transformed from one type to another (mechanical, electrical, chemical, heat,...). But every transformation results in a net loss of total energy. A heat pump WH inserts a mechanical transformation, for what was direct NG consumption....I could be wrong, but am blind to any flaws in my logic.

The flaw in your logic is that the first law of thermodynamics applies only to closed systems.

The house is not a closed system. It is exchanging energy with the environment. During the summer, heat is infiltrating through the building envelope. During the winter, heat is being lost through the building envelope.

Since you don't want to gain this heat in summer, and you don't want to lose this heat in winter, any of the heat that gets captured by the heat pump is free. Of course, the heat pump cannot actually capture all of this heat since its performance drops when it gets cold. That is why the OP's heat pump has a rated Energy Factor of 3.75, but the OP will only achieve an Energy Factor in the 2s.

dratkinson wrote: '

Sat Sep 18, 4:13 pm

If (a heat pump's) electric consumption were efficient, most would use electric heat. But we don't because NG heat is reported to be more efficient. So any transformation(s) that get between direct NG consumption, and heat produced, I believe, must be less efficient.

If (a heat pump's) electric consumption were efficient, most would use electric heat. But we don't because NG heat is reported to be more efficient. So any transformation(s) that get between direct NG consumption, and heat produced, I believe, must be less efficient.

Heat pumps are more efficient than natural gas water heaters, even when the electricity is generated by burning natural gas.

A natural draft gas water heater has an Energy Factor of 0.6. The OP can expect to achieve an EF of 2.0 in that climate, and natural gas power plants are 44% efficient in the current US energy grid. 2.0 * 0.44 = 0.88.

Heat pumps perform even better in warmer climates, where the heat pump can actually achieve its rated EF. 3.75 * 0.44 = 1.65. The heat pump is 2.8 times as efficient as burning natural gas on-site!

Cost is the main reason that people don't use heat pumps when natural gas is available. Electricity costs a lot more than natural gas, 4-5 times as much in some states. You may be putting less carbon dioxide into the air, but you'll pay more for the privilege.

The flaw in your logic is that the first law of thermodynamics applies only to closed systems.The house is not a closed system. It is exchanging energy with the environment. During the summer, heat is infiltrating through the building envelope. During the winter, heat is being lost through the building envelope.Since you don't want to gain this heat in summer, and you don't want to lose this heat in winter, any of the heat that gets captured by the heat pump is free. Of course, the heat pump cannot actually capture all of this heat since its performance drops when it gets cold. That is why the OP's heat pump has a rated Energy Factor of 3.75, but the OP will only achieve an Energy Factor in the 2s.Heat pumps are more efficient than natural gas water heaters, even when the electricity is generated by burning natural gas.A natural draft gas water heater has an Energy Factor of 0.6. The OP can expect to achieve an EF of 2.0 in that climate, and natural gas power plants are 44% efficient in the current US energy grid. 2.0 * 0.44 = 0.88.Heat pumps perform even better in warmer climates, where the heat pump can actually achieve its rated EF. 3.75 * 0.44 = 1.65. The heat pump is 2.8 times as efficient as burning natural gas on-site!Cost is the main reason that people don't use heat pumps when natural gas is available. Electricity costs a lot more than natural gas, 4-5 times as much in some states. You may be putting less carbon dioxide into the air, but you'll pay more for the privilege.

Hi All,

Contact us to discuss your requirements of Split system water heater. Our experienced sales team can help you identify the options that best suit your needs.

I've decided to build a small basement for a mechanical room and some storage (happy to have it cold storage too for meat freezer and wine) and wonder how how feasible it is to use a heat pump water heater  in a basement in a cold climate?

Would any heat generated from mechanical room be enough to prevent temps going below freezing in winter with heat pump running?

Would it be recommended or worth it to run radiant floor heat in the basement just in case of temps getting too cold or not worth it financially?  Trying to be smart with construction costs as definitely on a budget.

If use electric water heater, any heat from mechanical room can rise and add some warmth to house during the heating months.

Background:
Western Montana (Bitterroot Valley)
Electrical rates are cheap between $.068 ' $.076 / khw (mostly hydro)
Radiant floor heat planned in slab

Thanks!

Steve

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