What makes a thermostat smart?
Smart Thermostats Key Product Criteria
- ENERGY STAR certified smart thermostats are required to:
- Work as a basic thermostat in absence of connectivity to the service provider.
- Give residents some form of feedback about the energy consequences of their settings.
- Provide information about HVAC energy use, such as monthly run time.
- Provide the ability to set a schedule.
- Provide the ability to work with utility programs to prevent brownouts and blackouts, while preserving consumers’ ability to override those grid requests.
- In addition to these requirements, they must meet the temperature accuracy and standby criteria shown in Table 1.
| Table 1: Connected Thermostat Device Criteria |
|
| Parameter |
Performance Requirement |
| Static temperature accuracy |
≤ ±2.0 ⁰F |
| Network standby average power consumption |
≤ 3.0 W average |
| Time to enter network standby after user interaction (on device, remote or occupancy detection) |
≤ 5.0 minutes |
Finally, as shown in Table 2, EPA certified smart thermostats are required to meet the energy savings criteria for reduction in cooling and heating system runtime, and report electric resistance heat use for heat pumps. In order to demonstrate compliance with these energy saving criteria, smart thermostat service providers use EPA-provided software to analyze and combine a year of data from hundreds of their customers’ homes, reflecting how the thermostats were actually used, to calculate national savings metrics for heating and for cooling. The lower 95% confidence limit is similar to an average but takes into account the chance the particular homes that were sampled were all higher savers. The 20th percentile means that 4 out of 5 homes in the sample saved at least that much.
| Table 2: Connected Thermostat Energy Savings Criteria |
||
| Metric |
Statistical Measure |
Performance Requirement |
| Annual % run time reduction, heating |
Lower 95% confidence limit of weighted national average |
≥ 8% |
| Weighted national average of 20th percentiles |
≥ 4% |
|
| Annual % run time reduction, cooling |
Lower 95% confidence limit of weighted national average |
≥ 10% |
| Weighted national average of 20th percentiles |
≥ 5% |
|
| Average resistance heat utilization for heat pump installations |
National mean in 5 ⁰F outdoor temperature bins from 0 to 60 ⁰F |
Reporting Requirement |
For more information, please see the full smart thermostat ENERGY STAR specification (PDF, 641 KB).
Depending on where you live, the best candidate to save energy in your home is a smart thermostat. These devices offer the ability to monitor and adjust your home’s temperature even when you are away. More importantly, they can be used to automatically turn down your heating and cooling when it’s not needed. Smart thermostats that have earned the ENERGY STAR go through an independent certification process that verifies energy savings based on extensive field data. Among the first to be certified were NEST, ecobee, Carrier/Bryant, and EcoFactor. Each product uses slightly different features to help homeowners save energy, so do your research, and choose the ENERGY STAR smart thermostat that’s right for you.