Metering Alternative Home Energy

Wind Turbine at Sunrise Alternative home energy sources for the residential sector come from solar power panels (PV), solar thermal energy,  micro hydro and wind.  Since the generation of this energy is directly affected by the weather, short term output is unpredictable.

As a result, solar and wind power usually supplement the electricity provided by the utility while micro-hydro is more often found in remote, off-grid locations and used to charge battery storage systems.

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Cost of other alternative energy sources such as larger scale hydro, biomass, waste incineration, biofuels and wave power make them too expensive for direct application to the residential market.  Thus, from the standpoint of metering, our discussion will focus on solar power panels, solar thermal energy, micro hydro and wind power generation.

If you are looking for more comprehensive information on alternative energy itself, check out Top Alternative Energy Sources.  The site offers an in-depth look many forms of alternate energy, including wind, water, solar and geothermal.  For a look at the future of alternative energy check out Futuristic Alternative Energy.

Residential wind turbines is a field subject to misrepresentation, especially for those not well informed.  If you'd like to get informed check out Home Alternative for the latest updates on wind power.

When the sun shines brightly or the wind blows steadily the amount of power produced can exceed the electrical demand of a home, depending upon its size.   Most utilities will offer a credit or buy back the excess kilowatt-hours generated by alternative home energy.  Higher-end home energy monitor systems are well suited for metering this dynamic flow of energy.

Utility companies meter electric usage and alternative home energy output for the purpose of billing.  A home energy monitor system can serve as a check-and-balance mechanism to confirm that this billing is correct.  Here are a couple of examples of how higher end home energy monitors track this information:

eGauge Metering
Here is a graphic example of how the eGauge home energy monitor tracks a bank of solar photo voltaics over the period of one week:

Solar Photovoltiac Output Graph
Click image to enlarge.

The red line depicts the demand power (KW) being drawn and the pink area shows the energy (KWh) that is purchased from the utility.  The green line represents the power generated by the solar PV bank.  The white area under the green line is where the solar energy has replaced the energy from the grid.  The green area above the red line shows where surplus alternative home energy was generated which can be usefor credit or sold back to the grid.

The table beneath provides the legend and a summary of the power used vs. the power generated for the period.  By setting this period to match the billing cycle from the electric company one can verify that they are receiving all of the alternative energy credits to which they are entitled.

TED The Energy Detective Metering
Energy Inc.'s TED 5000 uses a different approach within its Footprints software to measure alternative home energy.  Power from the grid is tracked with one or more measurement transmitting units (MTU's). An additional MTU is used to track the generation of alternative home energy.

The output from these MTU's can be combined to provide a net kilowatt-hour measurement. Watts of power will appear as a positive number when more load is being consumed than is produced.  Conversely, if the output is negative, alternative home energy production will exceed the load and the excess can be sold back to the utility or credited to one's account.

The Footprints software dashboard can view each MTU independently, combined or a combination thereof.  In this example MTU's 1 and 2 messure total load and MTU 3 measures a subpanel within the MTU 2 load.  Net load is the sum of MTU 1 and 2 while MTU 3 is viewed as a stand alone unit.

MTU 3 could measure alternative energy generation just as easily.  It would return a negative value when alternative power was generated.  Net kilowatt-hours would be determined by adding all three MTU's together.

The Energy Detective Software Dashboard
                         Click image to enlarge.

Historical data is logged by hour, day, week and month.  It can be viewed in the Footprints software or can be downloaded as a .csv file into a spread sheet for further analysis.  The history within Footprints or the spread sheet data can be compared directly with your electric bill to verify energy credits.

We have only presented two examples here.  For additional information on how the various home energy monitors display alternative power data visit our Energy Monitor Dashboard page.  If you are interested in learning how to install an energy monitor to measure alternative power please visit our Tracking Renewable Energy Sources page.

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