Sensor Networks Geyser Energy Savings

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Introduction

In order to estimate Sensor Networks customer energy savings, we need to calculate the expected energy usage were devices not installed, and compare this to the actual, recorded energy usage (Note that these numbers rely on various assumptions, and represent a rough estimate).

Expected Usage

The Eskom average geyser usage is between 13 and 15 kWh per user/household per day[1]. For this report, we have selected a sample set of 665 Sensor Networks users. For each week between 1 Jan 2018 and 31 Dec 2019, we find the number of unique users (device serial numbers) that have sent telemetry data to the servers. This gives us an estimate for the number of customers using a device each week. We then estimate weekly Eskom-expected usage by multiplying this number of customers by 14 * 7 = 98 kWh (expected weekly usage based on Eskom numbers). Finally, we sum these values from each week to find total expected usage for the two-year period.

Estimated Total Usage

To estimate total usage for the sample of Sensor Networks customers, we consider all unique serials (customers) whose devices have sent telemetry data during the period. Energy usage is tracked in a cumulative way, so we can estimate total energy usage per customer for the period by finding their maximum recorded energy value. This value is recorded in Wh, so we convert to kWh by dividing by 1 000. We can then sum these values to find the total estimated usage for all customers.

Savings

The total expected usage for the period based on the above assumptions is 2 999 192 kWh. The estimated total usage is 1 475 141 kWh. The estimated total usage is 1 524 050 kWh less than the total expected usage (approximately a 50% reduction). At a rate of R1.80 per kilowatt hour (this rate will vary, as energy is charged at a cross section of rates for usage), the total savings for the period is R2 743 290. With 665 unique users, this represents an average saving of R4 125 per customer for the period, or R171 per month.

References

[1] http://www.eskom.co.za/sites/idm/Documents/20130919Eskomtrimmingbrochure.pdf