Getting the size right is the most important step in any solar installation. Too small, and your system cannot keep up with your usage. Too big, and you spend more than you needed to. Here is how to work it out yourself, step by step, before you even call an installer.
Step 1: List Your Appliances
Walk through your home and write down every electrical appliance you want to run on solar. For each one, note two things: the power rating in watts (usually printed on a label on the back or bottom) and roughly how many hours per day you use it.
Here are typical power ratings for common appliances in Bulawayo homes:
- LED lights (per bulb): 10W
- Ceiling fan: 60-75W
- TV (LED, 40-55 inch): 80-120W
- DSTV decoder: 25-30W
- Wi-Fi router: 10-15W
- Laptop charger: 60-80W
- Phone charger: 5-15W
- Fridge/freezer: 100-200W (but runs intermittently, so actual usage is lower)
- Microwave: 800-1200W (short bursts)
- Washing machine: 300-500W
- Iron: 1000-2400W
- Electric geyser: 2000-3000W
- Air conditioner (small room): 900-1500W
Step 2: Calculate Your Daily Energy Usage
For each appliance, multiply the wattage by the hours you use it per day. This gives you watt-hours (Wh). Add them all up to get your total daily energy consumption.
Example for a typical three-bedroom home:
- 8 LED lights x 10W x 5 hours = 400Wh
- 1 TV x 100W x 4 hours = 400Wh
- 1 decoder x 30W x 8 hours = 240Wh
- 1 router x 12W x 24 hours = 288Wh
- 1 fridge x 150W x 8 hours (compressor cycles) = 1,200Wh
- 2 phone chargers x 10W x 3 hours = 60Wh
- 1 laptop x 70W x 3 hours = 210Wh
- 1 microwave x 1000W x 0.3 hours = 300Wh
Total: roughly 3,100Wh (3.1kWh) per day
Step 3: Size Your Battery Bank
Your battery bank needs to store enough energy to cover your usage during the hours when solar panels are not generating (evening and night) and during load shedding.
A general rule: your usable battery capacity should be at least 1.5 times your daily evening/night usage. This gives you a safety margin and avoids deep-discharging the batteries (which shortens their life).
For the example above, if you use roughly 2kWh between 6pm and 6am, you want at least 3kWh of usable battery capacity. A 5kWh lithium battery (with 80-90% usable capacity) gives you about 4-4.5kWh of usable energy, which is comfortable.
Step 4: Size Your Solar Panels
Bulawayo gets excellent sunshine. On a clear day, you can expect roughly 5 to 6 peak sun hours. Your solar panels need to generate enough energy during those hours to cover your daily usage AND recharge the batteries.
For a 3.1kWh daily usage, adding 20% for system losses (wiring, inverter efficiency, temperature), you need about 3.7kWh of generation. Divide by 5 peak sun hours = 740W of panel capacity. So roughly 800W to 1kW of panels (two to three 450W panels).
Step 5: Choose Your Inverter Size
The inverter converts DC battery/panel power to AC for your home. It needs to handle the maximum load you will run at any one time.
Add up the wattage of everything that might run simultaneously. In our example, if the fridge, TV, lights, and router are all on at once, that is roughly 350W. Add the microwave for short bursts and you hit 1,350W. A 3kVA inverter handles this easily. A 5kVA inverter gives you room for growth and occasional high-draw items.
The Quick Rule of Thumb
If doing the calculation feels like too much, here is a rough guide for Bulawayo:
- Small flat or cottage: 2-3kVA inverter, 2.5kWh battery, 800W panels
- 3-bedroom house (standard usage): 5kVA inverter, 5kWh battery, 1.5-2kW panels
- Large house or high usage: 8-10kVA inverter, 10kWh+ battery, 3-4kW panels
Why a Professional Assessment Matters
This guide gets you in the right ballpark. But every home is different. Your roof orientation affects panel output. Your wiring setup affects what is practical. Your actual usage patterns might surprise you. A professional site assessment catches the things a back-of-envelope calculation misses.
Our team does free site assessments across Bulawayo. We will check your roof, look at your DB board, understand your usage, and recommend a system that actually fits your home. No obligation, no pressure.
Book a free site assessment or WhatsApp us. For pricing, check the pricing guide.