Read Your Electricity Bill Before You Go Solar: The Five Numbers That Matter

Every accurate solar estimate starts with your electricity bill. Five minutes spent reading it properly tells you more than any online calculator can guess.

Find these five numbers

• Units consumed: the kWh figure for the billing period, not the rupee amount
• Sanctioned load: printed in kW or kVA, it caps the system size your DISCOM will approve
• Tariff category: domestic, commercial, industrial or agricultural, which decides your rate and your subsidy eligibility
• Slab-wise energy charges: the per-unit rate rises as consumption rises
• Fixed charges and duties: these do not disappear when you go solar

Why the slab matters more than the average

Tariffs here are slabbed, so the last hundred units you consume cost far more than the first hundred. Solar shaves consumption off the top of the bill, which is the most expensive part. That is why a system cutting your units by 60 per cent can cut the rupee bill by more than 60 per cent.

Use twelve months, not one

A May bill inflated by air conditioning and a November bill with the fans off describe two different households. Add up a full year of units and divide by twelve before sizing anything. Our calculator's defaults — ₹8 per unit, and roughly 1 kW for every ₹1,000 of monthly bill — are a reasonable starting point, but your own twelve-month average beats any default.

What solar will not remove

Fixed charges, meter rent, electricity duty and municipal levies remain, and net metering settles net units over the billing cycle. Expect a much smaller bill rather than a guaranteed zero one, and be sceptical of anyone promising otherwise.

Then look at the roof

Once you know your annual units and sanctioned load, the remaining questions are shadow-free area and structure type. Run the numbers on our calculator, then book a survey so the estimate reflects your roof rather than an average one.