What does 1 GW of installed solar energy mean? How many houses can it power?
“What does one gigawatt of installed solar capacity mean?”, an editor from a general news outlet commented on my manuscript. “How many houses can the electricity power?”
I had a very rough idea of what types of power projects could be described as “ambitious” or “small-scale”, but admittedly, I had never considered what one gigawatt (GW) or one megawatt (MW) meant for an ordinary person, like myself.
I immediately googled for the answer but soon realized that the task was more arduous than I previously envisioned. The number of households that 1 GW of electricity can power range from 200,000 to 1,000,000 in the search results.
US-based Solar Energy Industries Association does provide the number of average homes that can be powered by 1 MW of solar photovoltaics (PV), but the figure varies by state, with California ranked the top.
I also searched for the installed capacity of the largest power plants in Hong Kong, Java, and Guangzhou, chewing over the narrative that 1 GW is equivalent to a specific percentage of those power plants. But do you know at all how much installed capacity your nearest power plant has and does the number make any sense? I don’t, and it makes no sense to me.
Finally, I consulted SEIA’s methodology to calculate the figure for Indonesia. My target is to find out how many houses 1 GW installed solar energy can power. The number is aimed at explaining a think tank’s campaign goal to boost the installed rooftop solar capacity to 1 GW in Indonesia.
Step 1. Identify the PV system performance estimate
The performance of a PV system is determined by a wide array of factors, including but not limited to the type of PV cells, local climate, temperature, and network. The average annual electricity consumption per household also varies by area.
I retrieved the performance estimates of solar PV in Indonesia from the Global Solar Atlas by the World Bank Group.
PV power output (PVOUT) is the figure that indicates the amount of electricity generated per unit of the installed PV capacity, usually measured in kilowatt-hours per installed kilowatt-peak of the system capacity (kWh/kWp) or gigawatt-hours per installed kilowatt-peak (GWh/GWp).
What does “peak” denote here? This is how a PV system works: The solar panels absorb the energy from the sun and produce DC power, and then an inverter converted the DC power to AC power that can be used, stored, or transmitted to the power grid.
The GW-peak or MW-peak rating refers to the direct current (DC) capacity of a solar PV module at maximum output under standard test conditions. The rating system is unique to photovoltaics because it is an intermittent electricity source and most other types of power generators directly produce alternating current.
As the think tank did not specify whether the targeted 1 GW referred to the DC or AC capacity, I assumed the number denoted the former.
One can find the average or median PVOUT through the Atlas’s Indonesia profile, or find the PVOUT values for eight sites in each month in the World Bank report (page 64).
I used the mean yearly PVOUT value of the eight sites in the World Bank report because back then I didn’t realize the Indonesia profile existed.
Indonesia’s yearly PVOUT = 1335.5 GWh/GWp [A]
Step 2. Identify the annual electricity consumption per household
The annual electricity consumption by the household sector and the number of households as of the end of 2019 can be found in the Handbook of Energy and Economic Statistics of Indonesia.
The annual electricity consumption by the household sector = 103,016 GWh
The number of households = 68700740
Therefore, the annual electricity consumption per household = 0.001499488943 GWh [B]
Step 3. Divide A by B
Therefore, the theoretical number of households 1 GW installed solar capacity can power = 1335.5/0.001499488943 ≒ 890637
The result is just a theoretical estimate for the readers to quickly grasp what 1GWp installed solar energy means. One can get a more precise number by using the city-specific PVOUT and household data and taking into account more real-life conditions that impact the PV system performance.
What data sources do you resort to in order to calculate the number of households a specific amount of installed solar energy can power? How do you explain 1 GW of power to your readers? Feel free to comment on the article or send me a direct message.
Read my recent work on the South China Morning Post, “Indonesia’s clean energy dream: a victim of coronavirus, or politics?”
