Read your bill before you buy solar
Ten minutes with an old bill stops you being sold a system twice the size you need.
The short version
- • Units decide your system size, not rupees.
- • Use twelve months of units, not one. Summer and winter are very different.
- • Find your sanctioned load. It limits how big your system can be.
Most bad solar purchases start the same way. Someone quotes you a size before anyone looks at a bill.
Your bill has what they need.
Look at units, not rupees
A unit is what a 1,000 watt appliance uses in one hour.
Your bill shows the units you used this month. Size your system on units. Rupees change when the tariff changes. Units do not.
Use a full year
A June bill and a January bill describe two different houses. Air conditioning can double your summer usage.
Add up twelve months of units and divide by twelve. That average is your number.
Most people cover the average and accept a small bill in July. Covering July fully means a much bigger system that sits idle in winter.
Find your sanctioned load today
It is printed on the bill. It is the maximum load approved for your connection, and your system has to fit under it. Want 10kW on a 5kW sanctioned load? You have to apply to raise it first, and that adds weeks.
A rough size check
One kilowatt of panels makes about four units a day, averaged over the year.
So 600 units a month is 20 units a day. Twenty divided by four is about 5kW.
That is a rough check. Your roof, your area and any shade change it.
Put in your average bill and your area, and it works out the real number.
Size my system