Summary

Ductless Mini-Split Heat Pumps for Residential Applications

Residential Ductless Mini-split Heat Pumps: Variable-Speed vs. Constant-Speed

Ductless split systems with non-inverter driven compressors have been available in the U.S. for decades. Within the last few years, the market has begun to shift to using inverter-driven compressors. Non-inverter driven compressors are still used however, typically due to lower first cost.

Synopsis:

Equipment that is capable of operating only as much as needed to meet the load is more efficient than equipment that can only operate at full capacity or off.

HVAC split systems, including ductless split systems, utilize variable speed (inverter-driven) compressors and fans. Constant speed on-off only compressors are good for locations where the load is constant, such as a small data or server room. However, for most applications, the load changes with the seasons and time of day. For these applications, inverter-driven motors on HVAC compressors can save significant energy.

Heat pumps with variable speed compressors have been available in other countries for many years, commanding more than 80% of the commercial and residential market combined in Japan, Europe and China. This technology is now widely available in the U.S.; manufacturers are offering more options to fit the U.S. market.

NEEA conducted a pilot program in 2009, training 900 installers and succeeding in getting 4,000 ductless heat pumps (DHPs) installed. The heat pumps were provided by 5 different manufacturers. By 2011, NEEA indicates that more than 13,000 ductless heat pumps had been installed in the Northwest, savings at least 40,500,000 kWh of energy (3,115 kWh/unit). Research showed that 90% of customers were satisfied with their ductless heat pumps and that customers reported a 25% to 50% reduction in their heating bills.

Energy Savings: 32%

Energy Savings Rating: Approved Measure What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Simple Payback, New Construction (years): 30.1 What's this?

Simple Payback, Retrofit (years): 33.7 What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

Details

Ductless Mini-Split Heat Pumps for Residential Applications

Residential Ductless Mini-split Heat Pumps: Variable-Speed vs. Constant-Speed

Item ID: 300

Sector: Residential

Energy System: HVAC--Heat Pumps

Technical Advisory Group: 2009 HVAC TAG (#2)

Synopsis:

Equipment that is capable of operating only as much as needed to meet the load is more efficient than equipment that can only operate at full capacity or off.

Baseline Example:

Baseline Description: Typical electrically-heated single-family home in the Northwest
Baseline Energy Use: 5.5 kWh per year per square foot

Comments:

The NEEA Residential Building Stock Assessment: Metering Study (April 2014) indicates an annual heating EUI for homes in the Northwest with electric baseboard heating of 17.74 kBtu/sf-year. This is equivalent to about 5.19 kWh/sf-year. About 12.3% of the region's homes are equipped with baseboard heaters as their primary source of heating. Note that the savings from homes with heat pumps (air source, ground source dual-fuel) will be much less than for homes heated with electric furnaces or baseboard systems. For residential AC, the mean region-wide annual energy use is about 0.3 kWh/sf-year (personal communication, Tina Jayaweera, Northwest Power and Conservation Council). Therefore, the combined heating and cooling electrical energy use is taken as 5.49 kWh/sf-year.

Manufacturer's Energy Savings Claims: Currently no data available.

Best Estimate of Energy Savings:

"Typical" Savings: 32%
Energy Savings Reliability: 6 - Approved Measure

Comments:

Per the Air-Conditioning, Heating and Refrigeration Institute (AHRI) this ET has Integrated Energy Efficiency Ratio's (IEER) in the high teens to mid twenty's. Existing equipment is in the low teens. Energy savings will depend on weather conditions for a given site. As the bulk of the energy used is for heating, a ductless heat pump COP of 3.5 is assumed (Daiken values range from 3.2 to 3.8). This results in a heating and cooling energy savings of about 71%---given that the whole house electrical heating requirements are served by multiple ductless heat pump heads. But, ductless heat pumps typically are defined as a zonal heating source and do not serve the entire household. In fact, Baylon reports that a ductless heat pump typically provides only 45% to 80% of the space heating in residential DHP retrofits. Geraghty studied 14 existing single-family homes with zonal heating systems and found that small, split-system heat pumps saved about 4,000 to 4,500 kWh/year. (from Baylon, "Ductless Heat Pump Engineering Analysis", December, 2012).

In 2008, BPA and the Northwest Energy Efficiency Alliance (NEEA) initiated a DHP pilot program targeting 2,500 single-family, site-built homes with zonal electric heating. The study drew from a broad range of sites across the Northwest and found average savings of approximately 3,049 kWh/year to 3,850 kWh/year across three heating climate zones. With an initial heating load of 5.5 kWh/sf-year, and assuming an average savings of 3,500 kWh/year, we obtain a post-installation annual energy use of 3.75 kWh/sf-year with a DHP energy savings of 31.7%. This savings value will be used in this analysis.

Note: This is a deemed measure under the October 1, 2014 BPA "Energy Efficiency Implementation Manual". The deemed amount is $800 to $1200 per unit depending upon existing heating source (baseboard versus electric forced air furnace).

Energy Use of Emerging Technology:

3.7 kWh per square foot per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: square foot
Potential number of units replaced by this technology: 1,727,411,771
Comments:

We can only count in the technical potential of those homes currently using electrical energy for space heating. Ductless heat pumps in the manufactured home and multifamily home markets are covered in ET #301 "Ductless Mini-Split Heat Pump for Manufactured Homes" and ET#302 "Ductless Mini-Split Heat Pump for Multi-Family Housing." According to estimates in the Northwest Energy Efficiency Alliance's (NEEA's) 2011 Residential Building Stock Assessment (RBSA), 34.2% of single-family homes in the Northwest are heated with electricity (Baylon, 2012 Pg 53, Table 51) but only 12.3% with electric baseboard heaters.

Homes with electric forced air furnaces have the option of switching to a conventional air-source heat pump and thus capture energy savings by utilizing the same ducted delivery system for heating and cooling needs rather than installing a single zone heating and cooling system. A BPA funded study does find that energy savings due to installation of ductless heat pumps in single-family homes with electric forced-air furnaces actually saves more energy---5,214 kWh/year---than a comparable installation in a home with electric baseboard heat. This is likely due to the reduction in duct leakage and losses through insulation. In such homes, the DHP tended to provide an average of about 77% of the heating energy (Baylon, 2012).

We make the simplifying assumption that electrically-heated baseboard heated homes are the same average size as each category of home with all heating sources, so to get an estimate of square footage for houses with baseboard heating, we multiply the total square footage of each type of home times the percentage of homes that are electrically heated in that category. The Residential Building Stock Assessment also indicates (in a roundabout manner) that about 6.1% of the single-family homes in the region use electric forced air furnaces. As these homes have a greater energy savings potential than do baseboard resistance heated homes, the baseboard home square footage is increased by an additional 6.1% x (5,214/3,500) = 9.08% of the total single family home sf.

Type of Home	No. of Homes	Avg. Size	Total s.f.	% Electrically Heated	s.f. Electrical
Single-Family	4,023,937	2,006	8,072,017,622	12.3% baseboard	992,858,167 sf
Single-Family	4,023,937	2,006	8,072,017,622	9.1% forced-air furnace	734,553,603
				Total baseboard equivalent sf	1,727,411,771

Regional Technical Potential:
3.04 TWh per year
347 aMW
What's this?

Regional Technical Potential of an Emerging Technology is calculated as follows:

Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)

First Cost:

Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $5.33
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.01
Baseline Technology Unit Cost (Equipment Only): $0.56

Comments:

Installed costs for single zone systems are around $3,500 for a 1-ton system and up to around $8,500 for a 5-ton system. This technology is available in up to eight zones on a single condensing unit, adding about $1,200 per zone. Prices vary greatly by contractor, and seem to depend on control systems selected, contractor familiarity with this technology, general availability of this technology within the given market (ie, where there are fewer qualified contractors, prices tend to be higher) the size of building, etc. The total installed cost for a 1.5 ton ductless heat pump (in mid-2014) was about $4,800 including wireless programmable controls. These costs are approximately 20% higher than an equivalent constant-speed system. Given that a one-ton unit will serve a residential area of 600 sf, the 1.5 ton unit captures some economies of scale and has a total cost of $5.33/sf.

The assumed baseboard heating system cost is $0.56/sf. (From Means, an 8-foot baseboard has a cost of about $193 and has a power output of 2 kW).

Cost Effectiveness:

Simple payback, new construction (years): 30.1

Simple payback, retrofit (years): 33.7

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Comments:

Cost effectiveness is a complicated subject for this technology. It is difficult to account for reduced maintenance and increased comfort and reliability. The cost effectiveness of this technology also depends on weather/climate conditions at the site and operational differences between owners.

Detailed Description:

Split systems can come with either a constant speed on-off compressor or an inverter-driven motor on the compressor. The on-off style does not last as long and is more costly to operate. Compressors with inverter-driven motors have a soft-start feature that allows the compressor to ramp up, avoiding the high inrush of current inherent with the on-off style. Compressors with inverter-driven motors have the ability to match the load rather than cycling on and off like the traditional style.

Manufacturers offering inverter-driven motors on compressor HVAC equipment include Daikin, Mitsubishi, Fujitsu, LG, and Sanyo.

The inverter-driven motor on a compressor is available with many styles of indoor air handlers, although different manufacturers offer different options: wall-hung ductless, ceiling cassette, floor radiator style, ducted fan coil, etc.

Standard Practice:

Traditionally, HVAC systems have constant speed on-off capacity compressors; constant speed fans on the indoor and outdoor units; and an expansion valve that can only operate at the fully open or fully closed position.

Development Status:

Readily available.

This technology has been used in the residential and commercial sectors for over 20 years in Japan, China and Europe. In fact, it dominates those markets, capturing more than 80% of the markets. To accommodate the U.S. market, the indoor unit options expanded from a ductless wall-hung unit to many other styles, including ducted, floor mount, ceiling mount and cassette.

Currently in the U.S., these systems are readily available from several large, well-established manufacturers who are well-positioned to expand capacity as needed due to increased interest in this technology. As the result of utility incentives and extensive marketing efforts by manufacturers and regional energy efficiency advocates, the number of installations have increased significantly. The Northwest Energy Efficiency Alliance estimates that as of 2013, over 65,000 of these systems have been installed in the Pacific Northwest (NEEA, 2014).

End User Drawbacks:

There is about a 20% premium on the first cost for this equipment. Until contractors get comfortable with the technology, it will continue to cost more than conventional equipment.

This technology performs very well if constantly operated, maintaining a steady temperature over long periods. They function less well in setback mode (turned off when the home is unoccupied, then turned on again when the home is occupied, or heat is desired.) (Harley, 2014.) Homeowners dissatisfied with the speed of heating with this technology might resort to electric resistance heat to bring the home to the desired setpoint, offsetting the savings for this technology. If the technology is to be operated in the most effective manner, the homeowner needs education on proper operation.

Operations and Maintenance Costs:

Comments:

Maintenance costs are not significant - the only regular maintenance required is filter cleaning, which can easily be performed by the homeowner.

Effective Life:

Comments:

The conventional standard existing technology without inverter-driven compressors usually has compressor failure and requires replacement in five to six years and system replacement in 12 to 15 years. Compressor failures are usually the result of the initial rush of current that is hard on equipment and the constant cycling on and off. Compressors with the inverter-driven motors have a “soft start” and shut down less frequently. Inverter-driven equipment modulates to meet the load. In addition to the soft start on the compressor, there is a similar variable speed feature for the indoor and outdoor unit fans, and the expansion valve is a modulating type. It is expected that inverter-driven systems should be operational for over 20 years, although the technology is new enough that this estimate cannot be verified with certainty.

Competing Technologies:

Equipment with constant speed compressors, constant speed indoor and outdoor fans, and open or closed only expansion valve.

Reference and Citations:

David Baylon, 08/12/2013. Ductless Heat Pump Impact & Process Evaluation: Billing Analysis Report
Ecotope, Inc.

AHRI, 08/24/2010. Performance Rating of Variable Refrigerant Flow (VRF) Multi-Split Air-Conditioning and Heat Pump Equipment
Air-Conditioning, Heating, and Refrigeration Institute

U.S. DOE, 06/24/2012. Ductless, Mini-Split Heat Pumps
U.S. Department of Energy

BPA, 01/01/2013. Field Test of Ductless Heat Pumps in Residences and Small, Commercial-Use Buildings
Bonneville Power Administration

David Baylon, et. al., 2012. Residential Building Stock Assessment Reports
Northwest Energy Efficiency Alliance & Ecotope

NEEA, 05/19/2014. NW Ductless Heat Pump Project
Northwest Energy Efficiency Alliance (NEEA)

David Baylon, 12/01/2012. Ductless Heat Pump Engineering Analysis: Single -Family and Manufacturerd Homes with Electric Forced-Air Furnaces
BPA Energy Efficiency Emerging Technologies Initiative

Rank & Scores

Ductless Mini-Split Heat Pumps for Residential Applications

2009 HVAC TAG (#2)

Technical Advisory Group: 2009 HVAC TAG (#2)
TAG Ranking:
Average TAG Rating:
TAG Ranking Date:
TAG Rating Commentary:

Market Potential

Ductless Mini-Split Heat Pumps for Residential Applications

Last Edited:

12/6/2012 3:24:02 PM by AngelaP

Market Segment:

This technology is applicable to many different market segments. For this specific technology, the applicable segment is for residential applications – either single-family homes or individual units of multifamily residential.

Regional Fit:

Mini-split heat pumps with variable refrigerant flow (VRF) are a very good fit for the Pacific Northwest. Our moderate climate makes heat pumps in general a very popular choice, great for retrofit and new construction. The technology can also benefit from the intense interest and success of ductless mini-split heat pumps for residential use. Many utilities in the region are already offering incentives on ductless heat pumps and, along with the Energy Trust of Oregon and BPA, have funded an active consortium promoting this technology, called the Northwest Ductless Heat Pump Project (http://www.nwductless.com/).

Zones:

Heating Zone 1, Heating Zone 2, Heating Zone 3, Cooling Zone 1, Cooling Zone 2, Cooling Zone 3

Performance Trajectory:

This technology has been used for over 20 years in the residential and commercial sectors in Japan, China, and Europe. In fact, it dominates the market there, capturing more than 80% of the market. It has become available in the U.S. within the last few years. To accommodate the U.S. market, the indoor unit options have expanded from a ductless wall-hung unit to many other styles, including ducted, floor mount, ceiling mount, and cassette.

Product Supply and Installation Risk:

There is no foreseeable product risk. Similar technology using CO2 as a refrigerant is currently being developed, which promises to be safer and more efficient than current VRF technology. In fact, it is already being marketed in Asia but is currently too expensive to compete in the North American market. Once fully developed, this technology may be used by the same manufacturers and will likely displace current technologies with little or no disruption. This CO2-based technology may create opportunities for new manufacturers; whoever cost-effectively develops the CO2-based technology first may have an advantage in the marketplace. There is no foreseeable shortage of product supply.

Technical Dominance:

Once this becomes a standard offering from more manufacturers, there is every reason to believe that the equipment will continue to improve over time.

Market Channels:

The market channels will be the HVAC dealers and distributors working with architects, and contractors.

Regulatory Issues:

Existing code-required minimum efficiencies will play a role in evaluating the requirements for equipment to be deemed accepted for incentives, now that AHRI and ASHRAE have adopted IEER testing.

Other risks and barriers:

The greatest barrier to implementation is initial cost. With financial incentives, this technology could become more cost effective, which would encourage its adoption by the target customers.

Basis of Savings:

Perhaps the cleanest method for specifying what would be deemed approved for incentives would be to specify that qualifed units must exceed the applicable energy code requirements by a certain percentage.The inverter-driven motors used in this equipment allow for up to 25 IEER and 10 HSPF.

Completed:

12/6/2012 3:24:02 PM by AngelaP