Guides
Energy and backup power guides
How to size solar arrays, orient the panels, choose a charge controller and an inverter type, work out the payback, charge a battery properly, size a UPS or a standby generator and what it costs to run, and find where the units on the bill go.
Backup and renewable power in Pakistan is sized badly more often than it is sized well: arrays that never fill the batteries, generators that stall on the first motor start or idle at a quarter of their rating for years. These guides walk through the arithmetic, and pair with the energy calculators that do it for you.
How to size a solar system
A step-by-step method for sizing a rooftop or off-grid solar system in Pakistan: measure the energy, find the peak sun hours for your site and worst month, apply honest losses, then choose panels, battery, inverter and cables that fit each other.
Read guide →How to size a UPS
What a UPS is for and what an inverter is for; VA, watts and the power factor trap; the three topologies of IEC 62040-3; runtime, Peukert and the C-rate; measuring the real load; generators and UPSs; the worked example; and the installation details that decide battery life.
Read guide →How to size a standby generator
Running load, motor starting, kW against kVA, prime and standby ratings, derating for heat and altitude, and the trap of an oversized diesel: how to arrive at a generator size that starts everything and still runs healthily.
Read guide →What a generator costs to run
Litres per kWh, not litres per hour; the fuel line and why a lightly loaded diesel is expensive twice; reading the datasheet; the diesel unit against the grid and against solar; how sizing and cost interact; the service costs nobody writes down; and what cuts the bill without a new set.
Read guide →How to orient solar panels
Why the best tilt is a little less than the latitude, why direction matters more than tilt on a real roof, what an east or west roof costs, when adjusting twice a year is worth it, and how dust and the tariff change the answer.
Read guide →Grid-tied, hybrid or off-grid
How grid-tied, hybrid and off-grid solar systems work, what anti-islanding means during load-shedding, the "solar UPS" market and what to demand of a hybrid inverter, batteries for each case, sizing in a paragraph each, net-metering approvals and the meter, and what we honestly recommend.
Read guide →Solar payback and net metering
The three numbers that decide a solar payback: specific yield and where to get it, the self-consumption share the quotation never states, and the export credit; how net metering works at the DISCO; what a quotation should show; financing; a worked 10 kWp example; and when solar does not pay.
Read guide →Choosing a solar charge controller
What a charge controller does; PWM as a switch and MPPT as a converter; the voltage window set by the coldest morning and the hottest afternoon; the 1.25 current factor; how to read a controller datasheet; a worked two-string example; and the installation errors seen in Pakistan.
Read guide →Where your electricity units go
A unit is a kilowatt-hour, and what an appliance costs depends less on its rating than on how much of the time it actually draws it. The arithmetic for the air conditioner, pump, geyser, fridge, fans and lights of a Pakistani home, the slab trap, standby loads and how to measure.
Read guide →How long a battery takes to charge
Charge efficiency, the three stages of a charger, C-rate limits by chemistry, why the absorption stage cannot be hurried, what solar changes, and the load-shedding arithmetic that kills lead-acid batteries by never letting them fill.
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