# T24 Solar & Energy Storage Calculator: Calculations Reference

Source: T24 CHEAT SHEET v3.xlsx

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## Inputs

| Field | Description |
|---|---|
| Building Type | One of: Multifamily, Grocery, Office, Retail, School, Warehouse, Hotel, Medical Office, Restaurant |
| Conditioned Floor Area (CFA) | Total conditioned square footage |
| Dwelling Units | Number of dwelling units (only used for Garden Style MF calculation) |
| Zip Code | California 5-digit zip code, used to look up Climate Zone and Electric Utility |

## Lookups

**Climate Zone:** Each California zip code maps to a climate zone (CZ 1–16). The lookup table contains 2,694 California zip codes.

**Electric Utility:** Each zip code maps to an electric utility company name. The lookup table contains 31,633 US zip codes with utility name and residential rate.

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## Calculation 1: Garden Style Multifamily (3 Stories or Less)

This calculation always uses the MF Low Rise factor table regardless of the selected building type. No energy storage is required.

### Formula

```
Solar kWdc = (CFA × A) / 1000 + (Dwelling Units × B)
Budget Cost = Solar kWdc × $3,000/W
```

### Low Rise Factors by Climate Zone

| Zone | A | B |
|---:|---:|---:|
| 1 | 0.793 | 1.27 |
| 2 | 0.621 | 1.22 |
| 3 | 0.628 | 1.12 |
| 4 | 0.586 | 1.21 |
| 5 | 0.585 | 1.06 |
| 6 | 0.594 | 1.23 |
| 7 | 0.572 | 1.15 |
| 8 | 0.586 | 1.37 |
| 9 | 0.613 | 1.36 |
| 10 | 0.627 | 1.41 |
| 11 | 0.836 | 1.44 |
| 12 | 0.613 | 1.40 |
| 13 | 0.894 | 1.51 |
| 14 | 0.741 | 1.26 |
| 15 | 1.560 | 1.47 |
| 16 | 0.590 | 1.22 |

---

## Calculation 2: Commercial / High-Rise MF (4+ Stories)

This calculation uses building-type-specific factors. Energy storage is required.

### Formulas

```
Solar kWdc    = (CFA × A) / 1000
ESS kWh       = Solar kWdc × B / √D
ESS kW (peak) = Solar kWdc × C
Budget Cost   = (Solar kWdc × $3,000/W) + (ESS kWh × $1,100/kWh)
```

Where D = 0.90 (constant for all building types).

### Factor A (Solar Sizing) by Building Type and Climate Zone

| Zone | Multifamily | Grocery | Office | Retail | School | Warehouse | Hotel | Medical Office | Restaurant |
|---:|---:|---:|---:|---:|---:|---:|---:|---:|---:|
| 1 | 1.82 | 2.62 | 2.59 | 2.62 | 1.27 | 0.39 | 0.39 | 0.39 | 0.39 |
| 2 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 3 | 1.82 | 2.62 | 2.59 | 2.62 | 1.27 | 0.39 | 0.39 | 0.39 | 0.39 |
| 4 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 5 | 1.82 | 2.62 | 2.59 | 2.62 | 1.27 | 0.39 | 0.39 | 0.39 | 0.39 |
| 6 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 7 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 8 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 9 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 10 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 11 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 12 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 13 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 14 | 2.21 | 2.91 | 3.13 | 2.91 | 1.63 | 0.44 | 0.44 | 0.44 | 0.44 |
| 15 | 2.77 | 3.53 | 3.80 | 3.53 | 2.46 | 0.58 | 0.58 | 0.58 | 0.58 |
| 16 | 1.82 | 2.62 | 2.59 | 2.62 | 1.27 | 0.39 | 0.39 | 0.39 | 0.39 |

### Factors B and C (ESS Sizing) by Building Type

| Building Type | B (kWh factor) | C (kW factor) |
|---|---:|---:|
| Multifamily | 1.03 | 0.26 |
| Grocery | 1.03 | 0.26 |
| Office | 1.68 | 0.42 |
| Retail | 1.03 | 0.26 |
| School | 1.87 | 0.46 |
| Warehouse | 0.93 | 0.23 |
| Hotel | 0.93 | 0.23 |
| Medical Office | 0.93 | 0.23 |
| Restaurant | 0.93 | 0.23 |

---

## Budget Cost Assumptions

| Component | Unit Cost |
|---|---:|
| Solar PV | $3.00 / Wdc |
| Energy Storage (ESS) | $1,100 / kWh |

---

## Worked Example

**Inputs:** Retail, CFA = 22,520 sq ft, 0 dwelling units, Zip 92307 (Climate Zone 14)

**Garden Style MF:**
- Solar = (22,520 × 0.741) / 1,000 + (0 × 1.26) = 16.69 kWdc
- Budget = 16.69 × $3,000 = $50,061.96

**Commercial / High-Rise:**
- Solar = (22,520 × 2.91) / 1,000 = 65.53 kWdc
- ESS kWh = 65.53 × 1.03 / √0.90 = 71.15 kWh
- ESS kW = 65.53 × 0.26 = 17.04 kW
- Budget = (65.53 × $3,000) + (71.15 × $1,100) = $274,865.04