# Demand Flexibility: A Review of Quantification Methods, Models, and Required Data
## 3 Results
### End-Uses Analyzed  
The studies reviewed include a variety of end-uses and energy systems. Most consider multiple load types per building [3; 9; 10; 13; 16; 17; 22; 23; 29; 34; 37; 38; 44; 45; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 64; 69] while others narrow down their focus on a particular end-use [1; 11; 14; 15; 20; 25; 27; 30; 31; 33; 35; 36; 39; 47; 50; 51]. There were clear trends regarding which end-uses were primarily focused on for each sector. For example, lighting [36; 62] and space conditioning [5; 14; 15; 17; 20; 29; 31; 33; 35; 37; 44; 51; 53; 59; 60; 62] were major foci for commercially focused research studies. Studies that either focused on residential research or included it in addition to the analysis of other sectors considered appliances that were commonly found in households. Figure 3 illustrates the major appliances of focus in residential studies. For instance, [3; 10; 13; 23; 54; 69] included clothing washers and driers. Moreover, [3; 10; 13; 23; 45; 54; 64; 69] included dishwashers in their analyses. Space and water conditioning was a major focus as well [1; 3; 4; 10; 11; 13; 15; 16; 22; 23; 25; 27; 30; 31; 32; 33; 38; 45; 52; 57; 59; 60; 62; 63]. EVs and electric vehicle supply equipment (EVSE) [10; 13; 34; 36; 47; 50; 63; 64] were a common focus for both commercial and residential studies; they are an emerging end-use with potentially high demand commonly found in either type of building. While residential and commercial sectors have broadly defined end-uses that are commonly found in buildings of each sector, industrial studies required more specialized approaches to characterize the processes present [6; 7; 8; 9; 26; 46; 61; 67]. Illustrated clearly by authors in this field, space and water conditioning were a major contribution to residential and commercial demand making them common inclusions in studies for these sectors. Specifically, [3; 17; 20; 29; 30; 33; 34; 37; 38; 51; 58; 59; 60] included HVAC systems in their work. Moreover, [10; 14; 16; 23; 25; 27; 48; 52; 53; 62; 63] included A/Cs, in particular. The authors of [3; 11; 22; 45; 58; 59] included water heaters. [10; 15; 22; 23] incorporated space heating into their estimations. More generally, [10; 13; 29; 32; 34; 35; 44; 57; 60] included heat pumps, [44; 61] included thermostatically controlled loads (TCLs), and [29; 31; 34; 37; 44; 57] included TES. TES could refer to either physical storage or thermal storage of a building. As noted by all authors of these studies, heating and cooling indoor air, as well as heating water, require significant amounts of energy, making them obvious inclusions in these studies. Even though studies were not comprehensive of all end-uses that could be found in each building type, many authors focused on commonly found appliances and energy systems based on ownership trends for the regions under study as illustrated by Table 2.  
Figure 3: Visualization of the share of appliances included in studies quantifying residential flexibility potential. Adapted from [5]. \begin{table}
\begin{tabular}{p{128.0 pt} p{128.0 pt} p{128.0 pt} p{128.0 pt} p{128.0 pt} p{128.0 pt} p{128.0 pt} p{128.0 pt}} \hline \hline
**Author** & **Methods** & **Case Study** & **Granularity** & **End-Uses** & **Metric(s)** & **Data Inputs** & **Sector** \\ \hline \multirow{2}{*}{[PERSON] et al. [1]} & \multirow{2}{*}{Statistical models for loads} & \multirow{2}{*}{X} & \multirow{2}{*}{Aggregate} & \multirow{2}{*}{TCL} & Power flexibility & \multirow{2}{*}{Demand, temperature (p.u.)} & \multirow{2}{*}{R} \\  & & & & PV, HVAC, battery, water heater, dishwasher, clothes & Forward flexibility (kW) & & & \\ \multirow{2}{*}{[PERSON] et al. [3]} & \multirow{2}{*}{MPC, flexibility model of building} & \multirow{2}{*}{X} & \multirow{2}{*}{Single} & & PV, HVAC, battery, water heater, dishwasher, clothes & Forward flexibility (kW) & \multirow{2}{*}{R} \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & & \\  & & & & & &