Product: HOMER Grid v1.2 and v1.3

If you have created a model in 1.2, then it is likely that your results will change when you recalculate in HGrid 1.3. When you open a model in 1.3 that was created in 1.2.8, you will get the suggestion to “Recalculate Results” as shown below.


 
The possible reasons for change in results for this could be:

1. Change in how Consumption Rates are handled
   1. Net rates now allow NET Negative
   2. “BUY” in 1.2 now has become “NetPurchase” in 1.3
   3. “SELL” in 1.2 now has become “NetExcess” in 1.3
2. Bug fix that affects any model with multiple simulations
3. Bug fix in peak shaving dispatch algorithm

Click on any of the links above for more details. 
 

Change in how Consumption Rates are handled

Net rates now allow NET Negative

Check for the following conditions when you open your model in 1.3.

1. Your tariff has any “Net Meter” rates as shown below.

 

 

1. Your model allows a Grid Sales (Grid Sale Limit is non-zero)
2. Your model has PV or battery that can sell excess to the Grid

If the above 3 conditions are met, then it is likely that your results will change. Below table explains the difference in calculation between 1.2 and 1.3.
 

Net Meter	1.2	1.3
Cost Calculation	If Net KWh > 0, then Cost= Net kWH * price ($/KWh)	Cost = Net kWh * price ($/kWh)

 
Note: The Net kWh is calculated over the Time of Use period and Charge period. For example, if the rate has a TOU period of Monday – Friday 9 am – 5pm, then Net kWh is = Sum of any grid purchases during the TOU – Sum of any grid sales during the TOU

 

“BUY” Rates have become “Net Purchase”

Check for the following conditions when you open your model in 1.3.

1. Your tariff has any “NetPurchase” rates as shown below

1. Your model allows a Grid Sales (Grid Sale Limit is non-zero)
2. Your model has PV or battery that can sell excess to the Grid

If the above 3 conditions are met, then it is likely that your results will change. Below table explains the difference in calculation between 1.2 and 1.3.
 

NetMeter	1.2	1.3
Cost Calculation	Cost = Energy Purchased * price ($/kWh)	If Net kWh >0, then cost = Net kWh * price ($/kWh)

 
Note: The Net kWh is calculated over the Time of Use period and Charge period. For example, if the rate has a TOU period of Monday – Friday 9 am – 5pm, then Net kWh is = Sum of any grid purchases during the TOU – Sum of any grid sales during the TOU

 

“SELL” Rates have become “NetExcess”

Check for the following conditions when you open your model in 1.3:

1. Your tariff has any “NetExcess” rates as shown below

 

1. Your model allows a Grid Sales (Grid Sale Limit is non-zero)
2. Your model has PV or battery that can sell excess to the Grid

If the above 3 conditions are met, then it is likely that your results will change. Below table explains the difference in calculation between 1.2 and 1.3.
 

NetMeter	1.2	1.3
Cost Calculation	Cost = (-) Energy Sold * price ($/kWh)	If Net kWh < 0, then cost = Net kWh * price ($/kWh)

 
Note: The Net kWh is calculated over the Time of Use period and Charge period. For example, if the rate has a TOU period of Monday – Friday 9 am – 5pm, then Net kWh is = Sum of any grid purchases during the TOU – Sum of any grid sales during the TOU
 

 

Bug fix that affects any model with multiple simulations

If you used the search space or the optimizer, then it might be that your results will change when you re-calculate in 1.3. This is because of a bug in 1.2 that was not clearing the calculations after each simulation.
 

Bug fix(es) in peak shaving dispatch algorithm

A few fixes have been made to the peak shaving dispatch.

1. Fix for negative energy losses in the battery
2. Fix for battery not selling to grid
3. Fix for ASM Battery Model