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ENERGY STAR^® Central Air Conditioner Rebate
Marshall Municipal Utilities offers rebates towards the purchase of new ENERGY STAR^® qualified central air conditioners when installed with MMU's load management receiver (ELF).

ENERGY STAR qualified central air conditioners have a higher Seasonal Energy Efficiency Ratio (SEER), which make them about 14% more efficient than standard models.

Seasonal Energy Efficiency Ratio (SEER) is a measure of equipment energy efficiency over the cooling season. It represents the total cooling of a central air-conditioner during the normal cooling season compared to the total electric energy input (in watt-hours) consumed during the same period. New split system central air conditioners manufactured after January 23, 2006, are required to have a minimum SEER rating of 13.

 ENERGY STAR^® qualified models with a SEER rating of 14 or greater are eligible for a $100 per ton rebate. You will also receive a $3 monthly credit on your utility bill for 4 summer months as part of our Load Management Program.

To download a rebate application form, click here: ENERGY STAR CENTRAL A/C & HEAT PUMP Rebate Form

ENERGY STAR^® Heat pump Rebate
Marshall Municipal Utilities offers Rebates towards the purchase of new high efficiency Geothermal or qualifying Air Source Heat Pump heating and cooling systems.

To download a rebate application form click here: ENERGY STAR CENTRAL A/C & HEAT PUMP Rebate Form

Ground Source heat pumps are eligible for a $200 per ton rebate.

Geothermal Heat pump
A Geothermal or Ground Source heating and cooling system will provide you with year-round comfort at dramatically lower prices than other, less efficient systems. Geothermal Heat Pumps use the earth as a heat sink in the summer and a heat source in the winter, and therefore rely on the relative warmth of the earth for their heating and cooling source. Through a system of underground (or under water) pipes, they transfer heat from the warmer earth or water source to the building in the winter, and take the heat from the building in the summer and discharge it into the cooler ground. Therefore, Geothermal Heat Pumps don't create heat; they move it from one area to another. For every watt of energy consumed by a geothermal heat pump, 2½ to 4 watts of heat will be put out. Because this system uses heat from the ground, annual operating expenses can be 35% to 70% lower than most other heating systems available. In addition to lower utility bills, you can also receive valuable rebates from MMU on your purchase of a geothermal system.

Air Source heat pumps are eligible for a $150 per ton rebate. You will also receive a $3 monthly credit for 4 summer months on your utility bill as part of our Load Management program.

Air Source Heat Pumps operate by moving or transferring heat, rather than creating it. During the summer, a heat pump captures heat from inside a home or business and transfers it to the outdoor air through a condensing unit. During the winter, the process is reversed. Heat is captured from outdoor air (even at temperatures below freezing), compressed, and released inside.

The key to understanding how a heat pump works is that even when it is very "cold" outside there is heat energy in the air. Air would need to be -460 degrees F ("absolute zero") for there to be no heat energy. A day that is 20 degrees F outside is 480 degrees F above absolute zero. 70 degrees F is 530 degrees F above absolute zero. So a heat pump only has to move the heat uphill a relatively small distance. It uses the "refrigeration cycle" to do this.

The Heat Pump Refrigeration Cycle
A refrigerant is a fluid which vaporizes (boils) at a low temperature. The refrigerant circulates through tubes ("refrigerant lines") that travel throughout the heat pump. We'll begin our description of the refrigeration cycle at point A on the illustration below, which describes the heat pump when it is heating the house.

At point A the refrigerant is a cold liquid -- colder than the outdoor air. The refrigerant flows to the outdoor coil (point B). This coil is a "heat exchanger" with a large surface area to absorb heat from the air into the colder refrigerant. The heat added to the refrigerant causes the fluid to vaporize, so this heat exchanger is called the "evaporator coil" during the heating cycle. When materials change state (in this case from liquid to gas), large amounts of energy transfer take place.

At point C the refrigerant is a cool gas, having been warmed and vaporized by the outdoor air. It is too cool to warm the house, so that's where the compressor (point D) comes in. The compressor raises the pressure of the gas. When that happens, the gas temperature rises. One way to think about it is that the compressor concentrates the heat energy. The compressor is often thought of as the "heart" of the heat pump, since it does most of the work of forcing heat "uphill." The compressor also forces the now hot gas (point E) further into the cycle.

The indoor coil (point F) is where the refrigerant gives up its heat to the indoor air. A fan blows air past the indoor coil to distribute heat to the house. This cools the refrigerant to the point where much of it condenses, forming a liquid. In the heating season, the indoor coil is called the "condenser coil." This change of state results in a large transfer of heat energy.

The warm mixture of liquid and gas (point G) continues through the cycle to point H - the expansion device (sometimes called a "metering device"). This device reduces the pressure, causing the refrigerant, to become cold again - cold enough so that it is once again ready to absorb heat from the cool outdoor air and repeat the cycle.

Cooling with a Heat Pump
One advantage of a heat pump is that in the summer it works just like an air conditioner to cool the house. Most heat pumps have a "reversing valve" to switch the flow of refrigerant so that it pumps heat from indoors to outdoors.

Marshall Municipal Utilities also offers rebates for heating systems that qualify for our Residential Interruptible Rate.