Electric water pump is much cheaper to operate than a petrol one

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

16 March 2025

Michael Mulama is planning to buy a water pump for irrigation. He writes: “…even though our village is connected to electricity, my neighbours prefer petrol and diesel water pumps. I read your comparison of petrol versus electric fence cutters and I have been wondering if the same can be applied to water pumps. Please advise.”

Unfortunately, Mulama did not say which specific types of pumps he wants to compare and so, I took the liberty of picking one of each type. The most popular petrol-powered water pump has a 7-horse-power engine and can deliver up to 25,000 litres of water per hour. I know a few people with this kind of pump and I tested one recently to establish the fuel consumption rate.

It has a 3L-fuel tank which takes about Sh500-worth of petrol and this kept the pump running for about 45 minutes. In that time, it delivered about 15,000L of water.

On the electric side, the most popular model has 0.5-horse-power (370-watts) motor and it delivers a maximum of 2,500 litres per hour. Larger electric pumps which can carry over 20,000L/h are available but they require 3-phase power which I assume Mulama doesn’t have.

So, the decision largely depends on how quickly Mulama wants the water delivered. To get 15,000L using the small 370W electric pump would require about 6h of continuous running. So, the question boils down to this: how much does it cost to run a 370W motor for 6 hours?

Electricity is sold in kilowatt-hours (kWh) and one kWh is equal to 1,000 watt-hours. If we run a 370W device for 6 hours, the electric energy consumed is simply 370W x 6h = 2,220Wh, or 2.22kWh.

Now, I bought a power token worth Sh7,500 a few days ago and I got 263.8kWh of electricity. This lasts about one month in my house and it works down to about Sh28.43/kWh. So, if I was to run the 370W electric pump for 6 hours, it would cost me Sh63.11.

Let’s put these numbers head-to-head for a clear comparison: a petrol pump consumes Sh500 to deliver 15,000L of water while an electric one consumes just Sh63 to do the same job – albeit much more slowly.

The purchase costs are also quite different. The petrol-powered pumps range between Sh15,000 and Sh20,000 while the electric ones are cheaper at about Sh5,000 to Sh10,000. So, Mulama’s choice is simple: the electric pump is much more economical.