PV Electricity savings go to zero if export rate only set to zero

Hi

Version - 2015.06.30 (update 1)
System - MS Windows 7 SP1
Module - PhotoVoltaic (detailed), commercial

I have recently upgraded to Version 2015.06.30 of SAM and have found a change from version 2015.01.30. that I can not explain. If, for both "Flat energy rates" and "Time-of-use & tiered energy rates", the sell rate is set to zero, then the "Value electricity savings" in the cashflow are zero. (Note net metering is disabled.)

I have briefly tested with my models and the default models that are included with SAM and achieve the same result. From these tests it seems that the sell rate only is used to calculate total savings irrespective of whether the saving is from energy offset internally (self consumption normally at the buy rate) or from exported energy (normally at the sell rate) or a combination of both.

Have you changed from "PV behind the single meter" to a "two meter model", one for PV and for internal load? I can not seem to see a switch for this?

If you require any models, please let me know.

As an upgrade request I would really like to see more detailed workings for the the electricity savings in the cashflow model (excel) rather that the just final total $ figure. At a minimum import and export kWh and $'s saved would be useful and if possible broken down further by Tiered rates/times demand savings etc.

Thank you for creating and maintaining SAM

Regards
Mark

Dear Mark,

In the latest version of SAM, we revised the net metering calculations as follows:

With net metering: One bi-directional meter where sell rates are equal to buy rates except for monthly energy rollover with year end sell rate. The renewable energy system offsets peak demand and energy charges.

Without net metering (gross feed in tariff): Two uni-directional meters: 1) A system-to-grid meter measuring power sold to the utility at the sell rate(s) you specify, 2) a grid-to-load meter measuring power purchased from the utility at the buy rate(s) you specify.

Thank you for the suggestions for improvement. We plan to add more output variables to make it easier to analyze the utility rate results.

Best regards,
Paul.

Thanks your for the response.

For Australian commercial projects we have one net meter with differing buy and sell rates. This, I believe, was be the way "without net metering" worked in Sam in 2015.1.30. and earlier versions. I can not find a way of simulating this condition in the 2015.6.30 version of SAM. Is there one?

I understand SAM is paid by the US government and therefore targeted for the US market, but it would really be appreciated if a switch could be add to allow net meeting with different buy and sell rates to be re-instated else we can no longer use it in Australia. We will be stuck at version 2015.1.30 and not be able to use the enhancements such as battery integration.

Here's hoping.

Regards
Mark

Hi Mark,

Thank you for that information. There are also many different implementations of net metering here in the U.S. We are doing our best to design SAM to work for as many of them as we can without being too complicated to use.

Stay tuned...

Best regards,
Paul.