In many Kenyan homes the electric shower is the biggest single load on the bill, ahead of the fridge and the TV. Heating water takes a lot of energy, and it is also one of the easiest loads to move to the sun.
What one shower costs
Heating water is simple physics. A five-minute shower uses about 40 litres of water. Warming it from about 18°C to 40°C takes about 1 kWh of electricity in an electric shower, which is nearly 100% efficient at turning electricity into heat.
| Per shower | Family of five, per month | |
|---|---|---|
| Energy | about 1 kWh | about 153 kWh |
| Cost at the DC2 all-in rate of KES 28.30 | about KES 29 | about KES 4,300 |
In cooler highland towns the water starts colder and the showers run longer, so the figures rise. Showers alone can also push a household above 100 kWh a month, into the higher DC2 tariff band.
Option 1: a solar water heater
A solar water heater warms water directly in a collector on the roof and stores it in an insulated tank. It does not make electricity, so nothing is lost in panels or inverters, and on a sunny day it can heat a full tank without any power at all.
A well-sized system with an electric backup element typically covers most of a household's hot water, less in the cloudy months. If it supplies 75% of the family's hot water over a year, it saves about KES 39,000 a year. At an example installed price of KES 120,000, it pays back in about three years.
Points to check:
- Size the tank to the household: roughly 40 to 50 litres per person per day.
- Collector type: evacuated tube collectors cope better with cool, cloudy weather; flat plate collectors are robust and simple.
- Water quality: hard borehole water can scale up a collector; ask about an indirect system or a scale filter.
- Backup timing: set the backup element to heat only in the evening if the sun has not done the job, never in the morning before the sun comes up.
Option 2: solar panels and a hot water tank
If you are installing solar panels anyway, a hot water storage tank with an element can be heated from surplus solar power using a diverter. Heating the family's 5 kWh a day of hot water takes about 1.3 kW of extra panels, about three 620 W panels. This is simpler to install than roof plumbing and uses the same equipment as the rest of the solar system, but it converts sunlight less efficiently than a solar water heater.
Option 3: a heat pump water heater
A heat pump moves heat from the air into the water, delivering roughly three units of heat for every unit of electricity. The same family's hot water would cost about KES 1,450 a month instead of KES 4,300, from the grid or from solar panels. Heat pumps cost more upfront and work best in warmer areas.
Which one fits
| Solar water heater | Panels and a tank | Heat pump | |
|---|---|---|---|
| Uses electricity | Only the backup element | Surplus solar | About a third of an electric heater |
| Works in outages | Yes, while there is sun | Yes, with the solar system | Needs power |
| Best for | Homes, hostels, hotels, clinics | Homes already getting solar | Warm areas, larger hot water demand |
For hotels, boarding schools, hostels and clinics, where hot water use is large and steady, the savings scale up quickly, and a solar water heater is often the first energy project worth doing.
Plan your hot water and solar together
- The free solar calculator shows how many panels your daytime loads need, including a hot water tank.
- See how many solar panels a house needs and what a KPLC unit really costs.
- For hotels, schools and clinics, StimaPulse compares water heating, solar and storage options together; request an assessment.