Solar
Solar Water Heater vs Electric Geyser: Running Costs Compared
Short answer
Heating 100 litres of water by 35 °C takes about 4 kWh of electricity. At an assumed KES 25 per kWh that is about KES 100 per tank, or roughly KES 3,000 a month for one tank a day. A solar water heater supplies most of that heat from sunlight, which is why it often pays back faster than almost any other home upgrade.
How much energy does hot water use?
Water needs about 0.001163 kWh to raise one litre by one degree Celsius. For 100 litres heated from 20 °C to 55 °C (35 °C rise): 100 × 0.001163 × 35 = about 4.1 kWh. A 3 kW geyser element takes roughly an hour and a half to do this, ignoring heat lost from the tank.
What it costs to run
At an assumed KES 25 per kWh, 4.1 kWh costs about KES 100. One tank a day for 30 days is about 122 kWh, or about KES 3,000 a month. A family heating more water will pay more. Use your own tariff to recalculate.
Solar water heater vs electric geyser
| Electric geyser | Solar water heater | |
|---|---|---|
| Energy source | Grid electricity | Sunlight, with an electric backup element |
| Running cost | Highest of the two | Low; backup used on cloudy days |
| Upfront cost | Lower | Higher |
| Works in a power cut | No | Heating still works; pumping may need power |
| Needs roof space | No | Yes, facing the sun |
Ways to cut hot water cost
- Fit a timer so the geyser heats only when needed.
- Insulate the tank and hot pipes.
- Lower the thermostat to a safe but sufficient setting.
- Install a solar water heater or pair solar PV with a heating element.
Is a solar water heater right for you?
It makes most sense where hot water use is steady and high: family homes, hostels, lodges and hotels. It needs a sun-facing roof and a suitable tank position. See our solar water heating service.
Common questions
Does a solar water heater work on cloudy days?
Output drops, so most systems include an electric backup element that tops up the heat.
How long does a solar water heater last?
Well-made systems can last many years with basic care. Water quality and maintenance affect lifespan.
Can I power my geyser from solar PV?
Yes, but a geyser is a large load and raises PV size sharply. A solar thermal heater is often more efficient for hot water.