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Winter solar calculator for Pakistan

Three parts: generation and cleaning recovery, daytime heating and battery, and hot-water sizing with payback. Use your own tariffs, appliance loads and installed quotes to compare scenarios.

Soiling is your own assumption; days since washing do not determine it. Add your electricity tariff only if you want a PKR estimate.

Scenario watts and hours are editable starting points, not standards. Enter the actual nameplate watts where you know them.

Daytime appliances (10:00–15:00)
ApplianceWatts (editable)Hours (0–5)
Air conditioner
Storage geyser
Induction cooker
Room heater

Included in every half-hour slot and the inverter limit.

Other non-heating energy beyond the continuous watts. For the sample inverter check it is spread evenly over five hours.

Concurrent load in any slot must stay within this.

Enter your own fraction; no default is assumed.

Use this instead of the fraction if you have it.

For battery sizing.

Required for a nominal capacity.

Your own figure and scenario.

The value you give up by using a unit yourself.

Illustrative 40 L/person/day. Edit it for your household.

Your own climate and target temperature; no hidden climate factor.

The share of annual demand you expect solar to cover; required only for savings/payback.

Required for an electricity saving.

Required for an LPG saving.

A dated installed quote, not a market range.

More bathrooms can mean simultaneous demand one tank cannot serve.

PVGIS is a long-term model, not a winter weather forecast and not a measurement of Punjab smog. The winter tilt is an illustrative geometry comparison (rounded latitude + 15°), not an optimum or a roof structural recommendation. A qualified professional must check structure, connectors and wind loading before any mounting change.

How to read the results

The generation panel scales the stored PVGIS 1 kWp model by your system size. The soiling field is applied as an assumption on top; it is not an observed city figure. The heating panel packs your own requested hours into ten half-hour slots and reports whether they fit the inverter limit; it does not promise hourly PVGIS power. The water panel sizes to standard tanks up to 300 litres and asks for a custom design above that.

Source: NEPRA legal and regulatory documents.

Grid connection, net-billing and export rules differ by agreement and date. Check the agreement and tariff on your own electricity bill. The calculator does not declare an optimum between heating, LPG and exports.

Questions about the calculator

How many units does a 5kW and 10kW solar system produce in winter in Pakistan?

At Lahore's standard 32-degree tilt, the stored PVGIS model estimates 22.15 daily units for 5 kWp in December and 20.95 in January; 10 kWp doubles those figures. These long-term averages include 14 percent model system losses. Actual output varies with city, weather, shade and site condition.

How much does winter smog reduce solar panel output in Lahore and Punjab?

There is no measured Punjab smog-loss percentage in this dataset. Airborne smog reduces incoming light, while deposited dirt adds a separate soiling loss. Washing removes deposited dirt, not airborne smog. Enter a measured or assumed percentage in the calculator; a 10 percent scenario is not a city statistic.

How should I compare electric heating with exporting solar power under net billing?

It can be worthwhile when useful daytime heat replaces grid electricity or LPG spending worth more than the export credit you surrender. It is not always better: appliance demand, inverter limits, actual sunshine and your agreement matter. Compare your own costs and check the applicable NEPRA rules before deciding.

What is the best winter tilt angle in Lahore, Islamabad and Karachi?

There is no universally best roof angle. Our illustrative winter scenarios use 47 degrees in Lahore, 49 in Islamabad and 40 in Karachi, compared with standard scenarios of 32, 34 and 25 degrees. These are latitude-based comparisons, not optimized designs. Ask a qualified professional to check mounting and wind loads.

Is a glass-tube solar geyser better than an electric geyser running on solar panels?

An evacuated-tube collector heats water directly, while an electric geyser uses electricity generated by PV panels. The better choice depends on hot-water demand, installed cost, available solar energy and backup needs. Both need realistic cloudy-day planning. Compare tank capacity, warranties and written quotes; neither option wins for every household.

Source: JRC PVGIS 5.3 user manual.

Sources and methodology