How To Check A Solar Installer's Quote Against Your Own Load Sheet

Three Quotes On The Table

A reader wrote to me with a problem I recognized on sight, because my own drawer holds the same evidence: three solar quotes for one house, at 3, 5 and 10 kW, with prices far enough apart to change what a family can afford that year. His question was which installer to trust. It is the wrong question, and it was my wrong question too, until the week of meter readings settled the size. Trust is not the instrument. A load sheet is.

My sizing story, the three quotes and the 27.3 units a day that resolved them, is in the guide to How Many Solar Panels A 5 Marla House Actually Needs. This page is the paperwork half of that story: what I did with the quotes once the size was known, line by line, and the four places where the final contract changed because a sheet of my own numbers was attached to it. Bring a calculator. Every check below is arithmetic a quote should survive in front of you.

The Load Sheet Check, Step By Step

1. Start from your measured need, never from the quote. My house uses 27.3 units a day; at the planning figure of 4.2 units per kW per day, the need is 6.5 kW, which the home load calculator rounds to the 8 kW band. Any quote far from that line must explain itself in units, not in adjectives.
2. Multiply the panels. Count times rating is the only honest panel total: quote A offered 18 panels at 550 W, which is 9,900 W against a 6.5 kW need. Quote B offered 9 at 580 W, 5,220 W. Quote C offered 14 at 580 W, 8,120 W, the band I bought.
3. Match the inverter to the panels and the sanctioned load. The inverter should sit at or near the panel total, and the system size must respect the cap NEPRA's rules set against your sanctioned load. If the inverter is much smaller than the array, ask where the midday power goes.
4. Interrogate the battery line. A hybrid quote should name the battery count, the amp-hours and the voltage, because stored energy is count times volts times amp-hours. A line that says backup included, with no count, is a line priced on trust.
5. Split the net metering line. Meter and connection charges belong to the DISCO; documentation work belongs to the installer. One combined round figure hides which is which, and the split costs the installer nothing to write down.
6. Check the name, not the promise. Net metering runs through certified installers, and the certified list is public: my check was the PPIB list of certified installers, where the company's name either appears or the conversation ends.

The load sheet did not make me an engineer. It made the quotes answer questions they were hoping nobody would ask.

The Line Items Where Padding Hides

None of these lines proves dishonesty on its own. Padding rarely announces itself; it accumulates in vague lines, each too small to fight over, until the total carries a motorcycle's worth of fog. The consumer net metering guide adds one more anchor: the AEDB framework's reference guide expects a certified company and an engineer's inspection certificate in the process, so a quote with no paperwork trail is missing something the system itself requires.

The Four Changes I Made Before Signing

• The panel line gained a brand, a model and a rating, with serial numbers to be written onto the invoice at delivery. A warranty attaches to equipment, not to adjectives.
• The inverter line named its model, and its size moved to match the 8,120 W array instead of sitting a size below it.
• The net metering fee split into the DISCO's charges and the installer's documentation work, each priced apart.
• The payment schedule rebuilt around milestones: delivery of named equipment, completed installation, and the bi-directional meter fitted. The last payment moved after the meter, where it protects the buyer instead of decorating the quote.

The installer signed all four changes without a fight, which taught me the final lesson of the exercise. The padding had never been a trap set for me personally. It was the default shape of a quote written for a customer with no numbers. Given numbers, the same company wrote a better quote.

How To Run This Check On Your Quote

Your version of this page needs two documents and one evening. The first document is the load sheet: a week of meter readings, taken the way I describe in my guide to Finding Your Real Daily Units, turned into a size with the 4.2 planning figure. The second is the quote itself, itemized. If it arrives as one round number, send it back for the itemized version before the evening starts; that request alone filters the market.

Then work down the steps in order: size against units, panels by multiplication, inverter against panels, batteries by count, fees by owner, name against the certified list. A quote that survives all six checks has earned a signature. A quote that fails one has earned a question, in writing, with the load sheet attached. Sign last. It is the only step in the whole purchase that cannot be revised later, and it should be the step with the fewest surprises left in it.