---
title: "Solar panel and inverter for a remote home"
subject: "Power Plant Design"
chapter: 1
key: "semester_8/power_plant_design:pv-sizing-lamps-tv-laptop"
source: https://www.bctengineer.com/q/semester_8/power_plant_design/pv-sizing-lamps-tv-laptop
site: BCT Engineering
---

# Solar panel and inverter for a remote home

Power Plant Design · Chapter 1: Energy Sources and Electric Power Generation

- Asked in: 2077 Chaitra, 6 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/power_plant_design/pv-sizing-lamps-tv-laptop
- Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-1

## Question

Find size of a solar panel and inverter system for a home in an isolated remote area, that has loads as in following table.

| Load Type | No. | Watt | Average Operating hours |
|---|---|---|---|
| Lamps | 3 | 10 | 4 |
| TV | 1 | 85 | 6 |
| Laptop | 1 | 65 | 8 |

Note: Make your own necessary assumptions.

## Short answer

Daily load is 1150 Wh. After inverter, wiring and battery losses, PV energy required is about 1654 Wh/day; with 5 peak sun hours and 0.9 derating, panel size is about 368 Wp, so choose 400 Wp. Inverter needs about 225 W, choose 300 VA; battery for 2 days autonomy, DoD 0.6 is about 230 Ah, choose 24 V, 250 Ah.

## Answer

The panel is sized from the daily energy demand plus all losses, divided by the peak sun hours; the inverter is sized from the total connected load with a safety margin.

**Assumptions:** all loads run on AC through an inverter; inverter efficiency 90%; wiring/other losses 10%; battery efficiency 85%; peak sun hours 5 h/day (typical for Nepal); panel derating factor 0.9; system voltage 24 V (because the daily energy is above 1 kWh).

#### 1. Daily energy demand

| Load | No. | W | Total W | h/day | Wh/day |
|---|---|---|---|---|---|
| Lamps | 3 | 10 | 30 | 4 | 120 |
| TV | 1 | 85 | 85 | 6 | 510 |
| Laptop | 1 | 65 | 65 | 8 | 520 |
| **Total** | | | **180** | | **1150** |

#### 2. Energy required from the PV array

$$
\begin{aligned}
E_{inv,in} &= \frac{1150}{0.9} = 1277.8\ \text{Wh} \\
E_{DC} &= 1.1 \times 1277.8 = 1405.6\ \text{Wh} \\
E_{PV} &= \frac{1405.6}{0.85} = 1653.6\ \text{Wh/day}
\end{aligned}
$$

#### 3. Solar panel size

$$
P_{PV} = \frac{E_{PV}}{\text{PSH} \times \text{derating}} = \frac{1653.6}{5 \times 0.9} = 367.5\ \text{W}_p
$$

Select a **400 Wp** array, e.g. four 100 Wp, 12 V panels (2 in series × 2 in parallel for 24 V).

#### 4. Inverter size
Total connected load = 180 W. With a 25% margin for starting surge and future load:

$$
P_{inv} = 1.25 \times 180 = 225\ \text{W}
$$

Select a **24 V DC / 230 V AC, 300 VA pure sine wave inverter**.

#### 5. Battery (for completeness)
With 2 days of autonomy, DoD 0.6 and battery efficiency 0.85:

$$
C = \frac{1405.6 \times 2}{0.6 \times 0.85 \times 24} = \frac{2811.2}{12.24} = 229.7\ \text{Ah}
$$

so a **24 V, 250 Ah** bank (two 12 V, 250 Ah batteries in series).

**Answer:** Solar panel ≈ 368 Wp → **400 Wp**; inverter ≈ 225 W → **300 VA**; (battery ≈ 230 Ah → 24 V, 250 Ah).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the daily energy demand?
   A. 1150 Wh
   B. 180 Wh
   C. 1653 Wh
   D. 900 Wh
   Answer: A. 120 + 510 + 520 = 1150 Wh. (Key point: Daily energy)

2. What energy must the PV array supply?
   A. 1150 Wh
   B. 1405.6 Wh
   C. About 1653.6 Wh/day after inverter, wiring and battery losses
   D. 2000 Wh
   Answer: C. 1150/0.9 x 1.1 /0.85 = 1653.6 Wh. (Key point: Energy from array)

3. How is the panel size obtained?
   A. 1653.6/5 = 331 Wp
   B. 1653.6/(5 x 0.9) = 367.5 Wp, choose 400 Wp
   C. 1150/5 = 230 Wp
   D. 1653.6 x 5 x 0.9
   Answer: B. Divide by peak sun hours and derating: 367.5 Wp, rounded to 400 Wp. (Key point: Panel size)

4. How is the inverter sized?
   A. Equal to daily energy
   B. Connected load 180 W with 25% margin = 225 W, choose 300 VA
   C. Half of load
   D. Panel rating
   Answer: B. 1.25 x 180 = 225 W, so a 300 VA inverter is chosen. (Key point: Inverter size)

## Related in Power Plant Design

- [Isolated PV sizing: lamps, fan and TV](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Apv-sizing-lamp-fan-tv) — Power Plant Design, chapter 1
- [Solar panel and battery for a house (7 h sun)](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Apv-sizing-12v-7h-sun) — Power Plant Design, chapter 1, asked 2×
- [Solar panel and battery for a house (6 h sun)](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Apv-sizing-12v-6h-sun) — Power Plant Design, chapter 1, asked 2×

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