How to use the calculator
Contractors and building management professionals in Minnesota can use this calculator to estimate potential energy, bills, and emission savings by upgrading from a standard AC/ gas furnace RTU to a dual fuel heat pump RTU, an RTU with an ERV, or a dual fuel heat pump RTU with an ERV. Results are estimates based on modeled average buildings from NREL’s ComStock database, with baseline results shown in blue, and upgraded systems configurations are shown in orange.
To use the calculator, input the closet equivalent building type, the average size of the RTUs, the gas and electric utility providers, and unit configuration. Unit configurations are below:
- Baseline: An AC/ Gas Furnace Rooftop unit
- HPRTU: a dual fuel heat pump RTU
- ERV for savings associated with a standard AC/ Gas Furnace RTU with an ERV, or HPRTU+ERV for a dual fuel heat pump RTU with and ERV
Calculator and Rates are updated annually. Rates shown were last updated December 2024.
Additional notes
All buildings are assumed to be in Minnesota TRM climate zone 3, unless otherwise noted. Climate zones can be found at appendix A of the Minnesota TRM, and generally climate zone 1 represents northern Minnesota, climate zone 2 represents central Minnesota, and climate zone 3 represents the Twin Cities Metro and southern Minnesota. Results assume a specific weather profile for each climate zone. Differences in weather conditions compared to this data can impact outcomes and differences between switchover temperatures.
Dual fuel heat pump RTUs are assumed to have a switchover temperature, or an outdoor air temperature at which they switch from heating with a heat pump to using gas backup, at 30°F. Lowering the switchover temperature will result in more energy emissions savings, but will also result in a higher energy bill.
Disclaimer
The potential savings values listed here are estimates for an example building. These estimates are generalized results from energy models and are intended to provide relative performance information to help rank options and make high-level decisions. These estimates should only be used when comparing scenarios for planning purposes. ERV calculations are performed assuming specific outside air % and ERV operation during operating hours. ERV effectiveness is dependent on a specific ERV product we believe to be representative of a typical ERV installation. Models are specific to the cases that are identified from NREL’s ComStock baseline database of models, and meaningful differences in these building and usage characteristics can result in different outcomes. The products collected to assemble the performance assumptions are from 2 product lines and include no variable speed HPRTUs. Products outside of those that are modeled may behave differently, impacting results