Passwords for Spreadsheet[edit source]
The default scenario is for a system in Kingston, Ontario, Canada. The "assumptions and sources" section in the calculator gives guidelines on how to change inputs based on location. Some of the inputs with default values are controlled from the Assump & Ref page. Our thought was this would make sure users made it to the Assump & Refs before making any changes. The password required to unlock the cells is included in the instructions on the Assump & Ref page.--Joshua 11:26, 22 December 2011 (PST)
Suggested upgrades[edit source]
To start with, the password production from the system size cell (PVSize) should be removed. That's probably the only cell most users would want to change, and it's marked as a user input, but is protected.
I find the "Associated Costs" section of the Inputs to be impractical to work with - it simply doesn't work the way we do in the industry. Due to the rapidly falling costs of some of the components, it would be useful to break out each part of the system separately as a per-watt cost. Likewise, some of the installation costs are fixed, engineering and permitting for instance, so we don't price that per-watt. Ideally there would be separate sections for the hardware in $/W and the "paperware" in raw $.
Specifically, I'd like to see the hardware section include inputs for modules, inverters, mounting, installation and electrical. The second section would include installation, electrical, engineering and permits. Yes, installation and electrical are in both sections, because some people price it one way and some another. Below these input sections would be a cell that calculates the total effective cost per watt. The rest of the sheet would work as it does now.
To demonstrate why this split up is useful, consider the price of panels over the last two years. I put SolarWorld 235's on my roof in early 2010 at a cost to me of $2.35 a watt. Today, their 255's are available for around 95 cents. On the contrary, inverter prices have remained almost flat, with a 3 kW inverter reducing in price from perhaps 40 to 35 cents over the same period. Install costs, due to new paperwork, have increased. So if all of these are rolled into a single number, it simply makes the user manually calculate the install $/W on their own, then type it in. Let's do that for them.
For reference, here in Ontario, following domestic content rules for a microFIT system, one would put in about $1.05, $.35, $.50 for flat-roof racking, $.60 for physical install and $3500 flat for electrical (including inspections and meter install), $1000 for engineering and permits. For non-domestic content using net-metering, $0.95, $.30, $.50, $.60, $2500 and $1000 would be appropriate. For 8kW example systems, that comes to $3.06 for microFIT, and $2.79 for net metering. Assuming a flat markup of 30% for the installation company, that's a little under $4.50 or $4.00/W, respectively. These seem like the right numbers at the time of posting in late 2012.
Another issue is the replacement inverter cost. It is very simple to find the $ cost of an inverter, or in $/W, but to express that as a percentage of the overall system cost? Uggg. I have these on my roof and I have no idea what that number is. Once again, I would recommend simply putting this in as a direct $ input, or simply using the figure entered into the inverter $/W field.
I'd be happy to make these changes to the sheet, if there is someone I can send the result to for uploading.
Maury Markowitz 09:02, 30 October 2012 (PDT)
- Hi Maury,
- Dr. Pearce would love if you made the changes you suggested and sent the spreadsheet to him.
- Thanks! --Lonny 16:44, 30 October 2012 (PDT)
Ok great, I'll work on it over the next little bit. One issue has popped up though... am I missing something, or is the calculator missing the derate factor? It asks for sunlight hours, but I don't see this being adjusted for downstream losses... Maury Markowitz 09:09, 31 October 2012 (PDT)
- Hi Maury,
- Dr. Pearce would love if you added the derate factor -- there is no factor currently for downstream losses. Again, it was previously used as a comparison/benchmarking tool. Please suggest and back up any assumption on derate factor that you include.
- Thanks! -- Kadra B/O Dr. Pearce
Error corrected in calculator on January 7, 2013[edit source]
Please note there was an error in the calculator. If you are using a version posted before Jan. 7, 2013 you should download the new version. The formula was correct in the paper and in "6. Assumptions", but not in the "5. Project Savings". There was an error was made in putting in the formula for the section "Annual Present Value Cost" for all cells. It should be (1+disc_rate)^t in columns X to AF.It was done correctly for "NPV Energy". You'll notice the numbers growing instead of declining under "Annual Present Value Cost". --Joshua 09:42, 7 January 2013 (PST)