Because the overall price difference is moderate, achieving overall savings requires shifting only a portion of electricity use to overnight periods.
Based on our study, shifting approximately 23.8% of total usage to overnight periods is sufficient to achieve overall savings.
In many households, EV charging represents a significant portion of total electricity use.
As a result, it is often sufficient to meet the required overnight usage for overall savings.
In our study, total savings of approximately $220 were observed compared to both flat and tiered rates.
Of this amount, about $79 was attributable to water heating.
Without shifting water heating to overnight periods, this benefit is lost, and an additional cost of approximately $24.65 is incurred, resulting in a reduction of about $100 in overall savings.
Shifting water heating overnight periods can significantly improve overall savings.
Water heating can represent a significant portion of household usage. In our study, shifting water heating to lower-cost periods resulted in a difference of about $100 in overall savings.
A controller helps ensure that water heating occurs at lower-cost periods to maximize overall savings.
To save on water heating under the Time-of-Day plan, the most important requirement is having a storage water heater with sufficient capacity. Without enough storage, hot water must be reheated during higher-priced periods, limiting potential savings.
Improving effective capacity—such as insulating the tank—helps retain heat longer and extend usable hot water.
Further savings come from two types of shifting:
- Usage shifting: moving hot water activities to lower-cost periods
- Heating shifting: scheduling water heating overnight or before on-peak periods.
In practice, sufficient storage is the foundation. Without it, the effectiveness of heating shifting is limited.
