Solar is not a gadget. It is a cost decision.
Most of what gets written about rooftop solar is a sales pitch with a number attached. This is the part that decides whether it is worth doing on your property, and there is not a single figure on this page we cannot stand behind.
WHAT SOLAR CAN AND CANNOT TOUCH
IllustrationThe more of your load runs in daylight, the more of the bill is in reach.
Fixed charges and demand charges do not move, whatever anyone promises you.
Four things decide whether this pays.
Price per watt is not one of them. Two identical systems on two identical roofs can have completely different cases, and the difference is always in this list.
How much you use in daylight
A rooftop makes power between roughly nine and five. If that is when your machines run, your lights are on and your cooling is working hardest, you are replacing power at the moment you use it and none of it has to travel through a policy first. A house where everybody is out until seven is a different calculation, and an installer worth hiring will tell you so rather than quoting anyway.
What your last unit costs
Tariffs are usually slabbed, so your last unit costs considerably more than your first. Solar takes units off the top of the slab, not off the bottom. That is why two buildings with the same monthly bill can have very different cases, and why the thing an installer actually needs from you is twelve months of consumption rather than one month's total.
The roof you actually have
Usable area is what is left after the water tank, the lift room, the ducting, the walkways and the shadow the building next door throws for two hours every afternoon. It is normally a good deal smaller than the roof looks from the ground. Anyone who sizes a system from a satellite image and a phone call has not measured it.
What your state does with the surplus
Whatever you generate and do not use goes back to the grid. Whether you are credited for it at the full retail rate, at a lower rate, or only up to a limited quota, is written by your state, not by your installer. It is the single biggest reason two identical systems in two states do not pay for themselves at the same speed.
Then there is how you pay for it.
Two questions people conflate constantly, and getting them the wrong way round is how a quote ends up looking better than it is.
SUBSIDY
A scheme with conditions, not a discount off the price.
Residential rooftop is supported centrally and several states add their own support on top. What you can claim depends on the connection being domestic, on the capacity involved, and on who owns the roof, which is why housing societies and rented premises need checking rather than assuming. Confirm where you stand before you compare prices. A quote that assumes support you cannot claim is not a quote, it is a hope.
FINANCING
Paying monthly asks a different question than paying once.
Bought outright, the question is how many years until the system has paid for itself. On a loan, the question is whether the monthly saving covers the monthly instalment, which is a different and usually easier test to pass. Ask for both, because an installer will naturally lead with whichever one flatters the quote in front of you.
Twelve questions to ask every installer.
Ask all of them, of all of them. The answers are how you tell a proposal from a brochure with a price on the last page, and any installer who resents being asked has told you something useful.
STRUCTURE
- What design wind speed has the mounting been rated for?
- Who signs off that the roof can carry the load?
- If the waterproofing is broken, who restores it?
- How is the array reached for cleaning once it is up?
EQUIPMENT
- Which module and which inverter, by make and model?
- What is the performance warranty, and who honours it?
- Is the cabling specified, or written as required?
- What happens to the warranty if the installer closes?
AFTER HANDOVER
- Who files for net metering, and by when?
- What if generation comes in under the estimate?
- What does maintenance cost from year two onward?
- What is deliberately not included in this price?
When every installer answers the same twelve questions against the same brief, the differences between their quotes are real differences in scope and equipment. That is the entire point of submitting a requirement here rather than making four separate phone calls.
Where rooftop projects actually go wrong.
Almost never in the place people worry about. Knowing the real failure modes is what turns a price comparison into a decision.
The roof, not the panels
Modules are commodities and they mostly behave. The failures that cost money are structural and electrical: mounting that was not rated for the site, penetrations that were sealed badly, cabling sized for the quote rather than for the run. None of that is visible in a price comparison, which is why the brief captures the structure before it captures the budget.
The paperwork clock
A system that is installed and not yet connected is generating nothing you can use. Net metering approval sits with the distribution company and it moves at its own speed. Ask who is chasing it and what happens if it stalls, before you agree a completion date that assumes it will not.
The estimate that was a brochure
Generation estimates vary with orientation, tilt, soiling and local weather. An honest one names its assumptions. A number with no assumptions attached is a sales figure, and it is worth asking what happens, contractually, if the system misses it.
What owners ask us first.
Plain answers, including the ones that argue against buying.
Is my roof big enough?
Usable area matters more than total area. What is left after tanks, walkways, ducting and afternoon shading is the number that counts, and it is normally smaller than the roof looks. That is exactly what a site survey establishes, and it is why the brief asks about obstructions rather than only square feet.
What if I do not use much power during the day?
Then the case is weaker without storage, and it is better to know that before you buy. Solar is at its strongest where consumption and generation happen at the same hours. If yours do not overlap, an installer should be talking to you about storage or about a smaller system, not about the same one at the same price.
How long do the panels last?
Modules degrade slowly and carry long performance warranties, which is why they are rarely the risk in a project. The parts that need attention sooner are the inverter, the mounting and the connections, so ask what the replacement plan is for those rather than only about the panels.
Do I have to maintain it?
Yes, mostly cleaning and monitoring. A soiled array looks identical to a working one from the ground, so generation has to be watched rather than assumed. Ask for the maintenance cost from year two as part of the quote, not as a conversation to have later.
Should I wait for prices to fall further?
That is your call and we are not going to pretend to know. What we would say is that the bill you pay while you wait is real money, and that the components have been getting cheaper for a long time without anyone reaching a moment where waiting stopped being an option.
Start on whichever side you are on.
Owners post a requirement in a few minutes. Installers pick up leads the same day they clear verification.