What Are the Energy Savings from VRF?
That’s the simple question everyone wants to ask – but
there is no simple answer. Every building is unique.
The GSA report estimates that VRF systems can achieve
30% and higher HVAC energy cost savings over older inefficient systems and minimally code compliant conventional systems. For retrofit applications, costs and energy
savings vary a great deal, making it impossible to estimate
a typical payback.
In the case of the federal government’s portfolio, GSA
recommends targeting existing buildings whose energy
usage is above the average (60.7 kBTU/square foot with
conventional systems) and whose initial incremental cost
for VRF is less than $4/square foot compared to CAV and
For examples of GSA and private-sector retrofit applications of VRF, see the following pages.
3) Assess lifecycle costs – The GSA assessment notes
that VRF systems may have higher maintenance, repair,
and replacement costs that offset some of the energy cost
savings. As a result, when analyzing the economics of VRF,
detailed lifecycle costs should be estimated.
The GSA report includes a sample lifecycle analysis
that compares a VRF system and a VAV electric reheat
alternative for a hypothetical building (see below). The
analysis includes costs for a dedicated outside air system
(DOAS) because VRF systems themselves do not integrate
outside air capability. While some buildings may have
adequate natural ventilation, most will require outside air,
but existing ductwork may be adequate to deliver volumes
that meet code requirements. In many climates, a DOAS
needs to preheat and precool outside air to a temperature
close to room conditions and its controls must coordinate
with a VRF system’s controls.
15-YEAR LIFECYCLE COST ANALYSIS OF RETROFIT ALTERNATIVES
The analysis considers a hypothetical 48,000-square foot office building with a cooling load of 120 tons.
The old system is VAV electric reheat, which is not providing adequate cooling. The retrofit project includes
total replacement of existing units and air distribution system. Two alternatives are considered.
Retrofit alternative 1: VAV with electric reheat
■ Four 30-ton packaged rooftop units
■ 10 terminal units per system, 40 terminal units
■ First cost: $1,008,800 ($21/square foot)
■ 10% energy cost savings compared to existing system
15-Year Lifecycle Cost Results
COST CATEGORIES PRESENT VALUE
First Cost HVAC Energy Cost Maintenance Repair/Replace Total
VAV $1,008,000 $457,278 $44,634 $5,644 $1,515,556
VRF $1,152,000 $279,447 $48,757 $19,828 $1,500,032
Net present value,
VRF - VAV $144,000 -$177,830 $4,123 $14,183 -$15,524
In this 15-year lifecycle case, the VRF alternative has a lower lifecycle cost with the identified parameters.
The VRF alternative has higher maintenance and repair/replacement costs. The present value of those costs
offsets almost 10% of the present value of the energy cost savings.
SOURCE: VRF LIFE C YCLE COST ANALYSIS, PNNL
Retrofit alternative 2: VRF with DOAS
■ Three 30-ton VRF compressor units
■ 20 fan coil units per system, 60 terminal units
■ One 20-ton DOAS unit
■ First cost: $1,152,000 ($24/square foot)
■ 45% energy cost savings compared to existing system