Disclaimer
The provided potential savings values are estimates for example homes matching each scenario. These estimates are generalized results based on field research 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 and do not replace load calculations or sizing recommendations given by professional contractors. In general, hybrid-heat systems offer the lowest operational costs for both propane and natural gas customers, while all-electric systems may increase bills for natural gas customers. Dual fuel or off-peak electric rate options, where available, can decrease costs even further for systems with both propane and natural gas secondary heat.
Rate and Utility Assumptions
Electric rates are updated on an annual basis for all utilities using Arcadia’s Genability Data Explorer. Natural gas rates are updated on an annual basis for all utilities using utility rate books, historical price information obtained from these utilities, and compliance filings with the Minnesota Department of Commerce. Electric and natural gas rates calculations include all applicable volumetric charges, including base costs and riders. In cases in which the user indicates that they do not know their natural gas rate or that their electric utility is not listed, a 2-year statewide average, weighted by historical climate data, is used in calculations. In cases in which the user indicates that they do not know their cost of propane, a weighted average of Minnesota weekly propane prices (October - March), is used in calculations. Note that for most utilities, dual fuel electric rates may require installation of an additional meter and/or use of an ASHP model compatible with load management controllers.
Technical Assumptions
All scenarios were modeled using National Renewable Energy Laboratory (NREL) typical meteorological year (TMY3) weather data corresponding to MN Technical Reference Manual (MN TRM) climate zones, depending on utility location. Heating design loads are representative of the median for a home of the selected type, vintage, and size and will not be exact calculations for a user’s individual home. These loads are aggregated values from NREL ResStock building models performed for MN homes with the stated characteristics and MN TRM climate zone. Energy consumption load shapes for gas, propane, and electric HVAC energy usage are estimated based on these loads and the information provided in the calculator inputs.
System performance is based on a field performance-adjusted 95% AFUE condensing furnace, 14 SEER/13.4 SEER2 single-stage AC, and mid-range ccASHP system archetype (16 SEER/15.2 SEER2, 9.5 HSPF/8.1 HSPF2, 2.1 COP @ 5°F) developed for the modeling tool.
The all-electric solution models a ccASHP boosted by concurrently operating electric resistance as needed. This allows the heat pump to deliver heat for a larger portion of the heating season for the example home modeled, minimizing the use of electric resistance backup, and decreasing operational costs. The hybrid-heat system models a 5°F switchover temperature and a 25°F switchover temperature. All systems are sized based on building load (dependent on load and home type inputs), using a similar approach to sizing as presented in the MN TRM.