Guides · Faisalabad, Lahore, Punjab

Energy Audit Before Industrial Solar: What to Measure First

Short answer

Before you size a solar plant for a factory, measure how the factory actually uses power: 12 months of bills, at least a week of load logging, your MDI, shift pattern, power factor and generator hours. These numbers decide the right plant size, whether a battery makes sense, and which cheaper efficiency fixes should come first. A plant sized from a single bill or a rough connected-load list is a guess.

This guide is a checklist of what to measure and why. It is written for factory owners and plant managers in Punjab who are comparing industrial solar proposals.

Why measure before you buy

Under net billing, a unit of solar you use on site is worth your full tariff, while a unit you export is credited at a much lower rate(/guides/net-metering-net-billing-pakistan/)]. So the most important question for a factory is no longer "how big can my roof go?" but "how much power do I reliably use during solar hours?" Only measurement answers that. Our guide to sizing under net billing explains the logic.

Measurement also prevents three common surprises after commissioning:

Diagram

Energy audit before solar

Measure

Loads, hours and bills

Reduce

Fix waste first

Size

Then size solar to what is left

A smaller, better-sized system often pays back faster.

How an energy audit differs from a site survey

A site survey looks mainly at the roof or land, the electrical room and the connection. An energy audit looks at how and when the factory consumes energy. For a home or small shop, bills and a survey are usually enough. For a factory, the two go together, and the audit should come first or alongside.

The checklist: what to measure

1. Twelve months of electricity bills

Collect bills for every meter on the site. From each, note:

Item on the billWhy it matters
Tariff category (B-1, B-2, B-3 and so on)Sets energy and fixed charge rates
Units (kWh), split into peak and off-peak where shownSeasonal pattern and time-of-use exposure
MDI (kW)Sets fixed charges; see what MDI means
Sanctioned loadLimits plant size under net billing; see increasing sanctioned load
Power factor or low power factor penalty lineShows correction needs; see power factor and solar

2. At least one week of load logging

Bills give monthly totals. A data logger or power analyser on the main incoming supply records kW, kVA, power factor and voltage every few minutes. Log a normal production week; if you can, add a week in a different season or production level.

From the log you get:

Example arithmetic (round illustrative numbers): if a unit logs a daytime load that rarely falls below 300 kW on working days but drops to 60 kW on Fridays after prayers and on holidays, a plant sized around the 300 kW working-day load will export heavily on low-load days. The design can either accept that export, add zero-export control, shift loads, or add storage. The log is what makes that choice visible.

3. Shifts and production schedule

Write down shift times, break times, weekly holidays, seasonal shutdowns and planned expansion. A spinning unit running three shifts and a garment unit running one day shift need very different solar and storage designs.

4. Major loads

List every large machine: motor rating, whether it has a VFD or soft starter, how many hours it runs, and when. Include compressors, chillers, boilers' feed pumps, dryers, furnaces, ovens and lighting. This shows which loads overlap with solar hours and which could be moved into them.

5. Power factor and the capacitor bank

Note the APFC panel's size, steps, controller settings and condition. Solar usually lowers measured power factor at the grid, so this must be planned; our power factor guide explains why.

6. Power quality

If the site has many drives, a furnace or a history of capacitor failures, record harmonics (THDv, THDi) with the analyser during the same log. See harmonics and power quality.

7. Generator hours and fuel

For each generator: rating, fuel (diesel or gas), monthly running hours, fuel consumption, and the loads it carries during outages. This sets the case for a solar and generator hybrid and for battery storage.

8. Load-shedding and outage pattern

How many hours a month is the grid down, at what times, and is the feeder industrial or mixed? This decides whether you need backup capacity or whether an on-grid plant is enough.

9. Thermal energy and gas

Gas for boilers, dryers and heaters is outside what solar PV replaces directly, but it matters for overall energy costs and any reporting to buyers. Record gas bills alongside electricity.

10. Space and structure

Roof areas, roof type and condition, shading, spare land and parking. Roof strength checks are covered in will my roof hold solar panels.

Fix the cheap things first

An audit nearly always finds savings that cost less than solar per unit saved:

Do these first, then size solar to the reduced load. Otherwise you may build a plant for consumption you were about to remove.

What the audit should produce

A useful audit ends with a short report that gives:

  1. A baseline: monthly units, MDI, power factor and generator use.
  2. A load profile chart for working days and low-load days.
  3. The recommended solar size for self-use, with the assumptions stated.
  4. Whether storage, zero-export control or load shifting is needed.
  5. Power factor and power quality actions.
  6. A list of efficiency measures with rough priority.
  7. A phasing option where budget or approvals require it; see planning a phased solar rollout.

Ask any solar company for the data behind its sizing. If a proposal states a plant size without showing your load profile, ask how it was chosen.

How Solar Works Pakistan uses load data

Load analysis and project feasibility are part of our normal process, done in-house by our engineers before design and quotation. For industrial sites we work from your bills, our site survey and, where the project needs it, load logging. We have served 300+ customers, including 50+ industrial clients, in sectors such as textiles, dyeing, looms and soap. See our industrial and commercial solar page.

Get today's price or a free site survey

Send us 12 months of bills for each meter, your shift pattern and generator details to start.

We serve factories and businesses throughout Punjab, and site surveys are normally free. You can also contact us online.

Frequently asked questions

Is an energy audit necessary before installing solar in a factory?

For a factory, yes in practice. Bills show monthly totals, but plant size under net billing depends on your daytime load, holidays and peaks, which only logging shows. Without it, the plant may export more or save less than expected.

How long should load logging run?

At least one normal production week, including start-up and shift changes. Two periods in different seasons give a better picture where production varies through the year.

What is the daytime base load?

It is the lowest load your factory draws during solar hours on working days. A plant close to that size uses nearly all its output on site, which matters under net billing.

Should I do energy efficiency before solar?

Usually, yes. Fixing air leaks, idle running and unregulated motors often costs less per unit saved, and it lets you size the solar plant to the lower load.

Does an energy audit include the generator?

It should. Generator hours, fuel use and the loads it carries decide whether a solar-generator hybrid or battery storage makes sense.

Can solar reduce my MDI?

Not reliably on its own, because one peak outside solar hours or during cloud sets the month. The audit shows when your peaks happen, and therefore whether load scheduling or storage is needed.

Sources

  1. Net billing facts (export credit, sanctioned-load limit) are carried over from our net metering and net billing guide, which lists its own sources, including the NEPRA (Prosumer) Regulations, 2026, SRO 251(I)/2026: https://ke.com.pk/wp-content/uploads/2026/04/8.-NEPRA-Prosumer-Regulations-SRO-251I2026-09-02-26.pdf

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