Current is measured, voltage is estimated
The clamps only measure current, so the voltage value must be estimated. On most of our energy monitors you can set and adjust the voltage. The default setting will usually be 240V.
This discrepancy is usually very small and easy to rectify if you need to. For example, if the supply voltage is around 243 volts (you can measure this with a plug-in mains power meter). So, even with the default setting of 240 volts the error will be of just over 1% on this front, which is not a big deal.
3 Tests of Accuracy: Normal Usage, High Usage, & Solar
Moving on to the testing, our partners in Australia ‘Reduction Revolution’ tested three basic scenarios. They categorized the first as ‘household consumption’ as it represents usage typical of most households. The second as ‘high consumption,’ equivalent to a small business site or very high consumption household. The third and final test was of solar PV power production off an inverter.
The data being compared was that of the wireless energy monitor vs. utility meter readings being taken at the meter box at the beginning and end of each test period.
Scenario 1 – Household Consumption
Energy consumption varied between 126 watts and 6.5kW during the test period. The test period represented an equivalent daily usage of about 16kWh/day. The resulting discrepancy was that the energy monitor over-estimated usage marginally by just 1.4%.
Scenario 2 – High Consumption (3 Phase)
Energy consumption varied between 778 watts and 8kW during the test period. The test period represented an equivalent daily usage of about 96kWh/day. In this case the energy monitor under-estimated usage by 5.5%.
Scenario 3 - Solar PV Power Generation
The solar PV inverter output was tested over an entire day. Taking the inverter's display screen as the 'correct' reading. In this case the Efergy Engage Hub for solar showed 5.12kWh of production whereas the inverter stated 5.09kWh. The energy monitor's reading was therefore an over-estimate of just 0.6%.