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Running Air Conditioner and other high power consuming appliances on Solar PV

By on April 22, 2016 with 197 Comments  

With increasing power tariffs, power cuts and decreasing solar panel prices, there is a lot of interest in people to adopt solar technologies. A few months back we started putting our research on solar technologies on our website and since then we have received hundreds of queries on solar PV and other solar technologies. One thing that we have noticed is very common is that people want to run Air Conditioners or water heaters or pumps using solar PV. Now these appliances are high power consuming appliances and thus their use of Solar PV needs a special attention. With this article we would highlight the specific challenges and solutions. It is also recommended that before going through this article, you read another article on our website: Solar electric, solar thermal, power generation, inverters, grid, off-grid: clearing the cobweb.

High Wattage and High Initial Current

Air Conditioners and Water Heaters are high wattage appliances. When a compressor of an air conditioner is running it needs high current. Below are some representative wattage based on air conditioner size:

Tonnage

Max Wattage

Max kVA (assuming 0.85 power factor)

1 Ton

1300 Watts or 1.3 kW

1.6 kVA

1.5 Ton

1900 Watts or 1.9 kW

2.4 kVA

2 Ton

2500 Watts or 2.5 kW

3 kVA

The wattage here is instantaneous power demand or the electricity required when all the components of air conditioner are running. But it varies during the running of an air conditioner because the compressor switches off when the temperature of the room reaches the level set in the thermostat. During the time the compressor is switched off, the electricity consumption is only for a few components in the air conditioner, which is much less. Also the initial starting current is high.

Similarly for electric water heaters the wattage requirement is 2-4 kW or 2000-4000 Watts. The high wattage is required only till the water is heated to a certain temperature.

To handle high loads of air conditioners or water heaters the inverters connected to a solar power generation system should be able to handle high load. So one needs about a 3 to 5 kVA inverter system to handle the same. Most commonly used home inverters are low kVA inverters that cannot handle this load. Also one would also want other appliances in a house to be running and not just the air conditioner, so this increases the overall size of the system.

High Energy Usage

Along with high current, an air conditioner also consumes a lot of energy during its operation. Depending on the tonnage of the AC and heat load in a room, an AC would consume about 1 to 2 units of electricity in an hour. A 1 kW Solar PV Panel would produce about 5-7 units in a day, which can get consumed in 4-5 hours of continuous running of an air conditioner. If other appliances in a setup are also added then the need of energy increases. And if the use of air conditioner is more, then the kW of solar panel required would be more and even the battery storage size needed would increase.

High Costs

All this adds up to very high costs. How much? Well it depends on size of your air conditioning system and your usage of the same. The system would include: Solar Panels, Charge Controllers, Batteries and Inverter. As we have published in an earlier post, cost of solar panels (just the panels) in India is about Rs 30-50 per Watt. So cost of a kW would be about Rs 30000-50000 (just for the panels). So if your usage of AC is high (more than 4-5 hours of one AC), then you need more kW of Solar Panels. More energy needed also means more batteries needed for storage, which will also add up to the cost.

Even the inverters that can handle load of 3.5 kVA and above are expensive and would cost upwards of Rs 1.5 lakh. On the whole the complete system to run just one 1 Ton AC for 4-5 hours can cost about Rs 2-3 lakhs.

Is PV the best technology for Air Conditioners?

Not really. In our article that we have mentioned above, we have talked about differences between Solar Thermal and Solar PV technology. Solar PV has much lesser efficiency as compared to Solar Thermal systems. There are some solar air conditioners available in the market that work on Solar Thermal principles (more about it on our article: Solar airconditioning: using sun’s energy when it most abundent and needed). Although Solar Air Conditioners have some limitations in working during nights, but if reducing electricity bill is your main motive, then Solar Air Conditioners provide much more value for money over using Solar PV for air conditioning. As per information that we have from our research, the air conditioners working on solar thermal principles are comparable to some of the efficient electric air conditioners in the market. Thus from a cost perspective they provide much more value.

Solar Water Heaters work better than PV for electric water heater

Solar PV should never be considered for water heating, as it is not an efficient use of PV. Solar Water Heaters, which we have discussed in a previous article (link) are much better solar solution for all water heating needs and much economical as well.

To conclude, if you have a lot of power cuts at your place and looking for a solution to run air conditioners during those periods, then Solar PV solution will work if the high cost is not a deterrent. But if electricity saving is your primary concern, then solar air conditioner offer lot more value for your money.

About the Author:
Abhishek Jain is an Alumnus of IIT Bombay with almost 10 years of experience in corporate before starting Bijli Bachao in 2012. His passion for solving problems moved him towards Energy Sector and he is keen to learn about customer behavior towards Energy and find ways to influence the same towards Sustainability. .

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