How LoadReserve works it out

Every number the planner shows comes from the calculation and data on this page. Where a figure is our own estimate rather than a published one, it says so.

What the result means

• Real daily backup, per cut. How long the battery can run your appliances at the start of your weakest cut, once the battery has settled (see below). It is the shortest of your cuts' backups, so it is the one to plan around.
• Hours covered. Of your daily load-shedding, how many hours had every appliance running.
• "A full battery would give…" The backup a fully charged battery gives at the start of a cut. When it is much larger than your real backup, the battery is not refilling between cuts: the recharge gap.

The calculation

LoadReserve steps through a day in 15-minute steps. In each step:

1. Grid on: your appliances run from the grid and the UPS charger refills the battery.
2. Load-shedding: your appliances run from the battery through the UPS. The battery supplies their average power divided by the UPS's efficiency, plus the UPS's own use.
3. When the battery reaches the UPS's cut-off, appliances switch off lowest priority first ("Can wait", then "Important").

Then the day is repeated with the battery starting where the previous day ended, until the battery's charge at midnight changes by less than 0.5% from one day to the next (at most 60 days). That settled day is the answer. Day one flatters a battery that never fully refills; a few days later it starts each cut lower, and that is what you live with.

Limits the calculation checks

• UPS output. Continuous watts = VA × power factor. If the appliances running at once need more, the UPS trips and nothing runs in that step. Cycling appliances such as fridges count at full power here, because they can all run at once.
• Starting surge. Motors draw several times their running power for a moment. An appliance cannot start if the others' running watts plus its starting watts exceed the UPS's surge rating.
• Charging. Limited by the UPS charger's current, the battery's highest safe charge rate, charging losses, and slower charging as the battery nears full.
• The bottleneck. To tell a battery that is too small from one that cannot refill, LoadReserve re-runs the day with a full battery at the start of every cut. If that covers everything, the limit is recharging; if not, it is the battery's size.

Settings we assume

Used when you have not entered your own. Each is a typical value for a home UPS, not a measurement of yours.

All are typical values chosen by LoadReserve (estimates).

Battery types

• Tubular / flooded lead-acid: A UPS runs the battery down to its low-voltage cut-off, about 80% depth of discharge, which is also the depth tubular batteries are rated for (Phoenix: 1250 cycles at 80%). Running this deep every day shortens battery life; 50% is gentler. Charging at 10% of Ah is at the low end of Trojan's 10-13%. Rate effects are not modelled yet: at high loads a lead-acid battery delivers less than its rated Ah.
• AGM / gel (sealed, 'dry battery'): Same cut-off assumption as tubular batteries; sealed batteries accept a somewhat faster charge.
• Lithium (LiFePO4): Manufacturers recommend 80-90% depth of discharge and a 0.5C standard charge.

Appliances

"Typical" is what the planner uses; "high" is an older or larger model. Duty cycle is the share of time an appliance actually draws power. Figures marked * are our estimates.

Sun hours

Solar energy per day = panel watts × peak sun hours × 75% (heat, dust, wiring and charging losses), spread evenly from 6–18:00. Peak sun hours are from PVGIS (European Commission), for panels at the best fixed angle. The planner uses the worst month unless you choose one.

Pakistan is outside PVGIS's satellite data, so these use its ERA5 weather reanalysis: coarser, and less reliable in hazy or smoggy months.

What the calculation leaves out

• Heavy loads on lead-acid batteries. At high currents a lead-acid battery gives less than its rated Ah, so backup with heavy loads may be shorter than shown.
• Battery age and temperature. An old or hot battery holds less.
• Solar timing. Sun is spread evenly over daylight, not peaked at noon.
• Your exact appliances. The figures are typical; yours may draw more or less. Change any figure in the planner if you know yours.

How it is checked

The calculation is tested against cases worked out by hand, including the recharge gap, before any change is published. If your real backup differs from what LoadReserve shows, that report is the most useful thing you can send us.

Sources

1. Champion Power Equipment: Generator Wattage Chart (manufacturer guide, accessed 2026-10-01)
2. TheGreenWatt: Appliance Wattage Chart: 60 Common Appliances (compiled from ENERGY STAR, DOE and EIA RECS 2020; refreshed April 2026) (compiled guide, accessed 2026-10-01)
3. GE Appliances: Refrigerator or Freezer - Normal Run Time (manufacturer support, accessed 2026-10-01)
4. OLX Pakistan: Ceiling Fan Watts, Electricity Consumption, and Cost to Run (retailer guide, accessed 2026-10-01)
5. Super Indus: 30 Watt Inverter Fans (manufacturer listing, accessed 2026-10-01)
6. Japan Electronics: Air Cooler vs AC: Which Is Best for Pakistani Home? (retailer guide, accessed 2026-10-01)
7. Super Indus: Air Cooler Price in Pakistan 2026 (manufacturer listing, accessed 2026-10-01)
8. AYS Online: Inverter AC Power Consumption per Hour in Watts - 1, 1.5 & 2 Ton (retailer guide, accessed 2026-10-01)
9. OLX Pakistan: Average Electricity Consumption of Inverter ACs in Pakistan (retailer guide, accessed 2026-10-01)
10. Electronics Pro: Fridge Wattage in Pakistan: Power Use and Inverter Needs (retailer guide, accessed 2026-10-01)
11. Toolz4Industry (listing of a Kirloskar product): Kirloskar 0.5 HP Chotu Domestic Water Motor Pump (0.37 kW, single phase) (retailer listing, accessed 2026-10-01)
12. Pilone Cables: Water Motor Wire Size: running current by motor size and direct-on-line starting current (manufacturer guide, accessed 2026-10-01)
13. AYS Online: What Is the Average Wattage of a Washing Machine in Pakistan? (retailer guide, accessed 2026-10-01)
14. Trojan Battery Company: Trojan Battery User's Guide (flooded deep-cycle): bulk charge at 10-13% of C20; avoid discharging beyond 80% (manufacturer guide, accessed 2026-10-01)
15. Solar Panel Prices PK (listing of a Phoenix product): Phoenix TX 1800, 185 Ah tall tubular battery: 1250 cycles at 80% DOD (retailer listing, accessed 2026-10-01)
16. Sunlith Energy: How to Read a LiFePO4 Battery Spec Sheet (standard charge rate 0.5C) (manufacturer guide, accessed 2026-10-01)
17. EcoTree Lithium: LiFePO4 Battery Depth of Discharge (80-90% recommended) (manufacturer guide, accessed 2026-10-01)
18. W11 Stop: Tubular Batteries Price in Pakistan (sizes on sale: 150-200 Ah and larger) (retailer listing, accessed 2026-10-01)
19. Solar with Ashfaq: Tubular Battery Prices in Pakistan, brand-wise list (retailer guide, accessed 2026-10-01)
20. Max Power: Build a Solar Backup System for Load Shedding in Pakistan (urban 4-10 h a day, rural 10-20 h) (retailer guide, accessed 2026-10-01)
21. Clopal: UPS vs Inverter in Pakistan: Difference & Which Do You Need? (retailer guide, accessed 2026-10-01)
22. Pakistan Observer: New Rates for UPS, Battery in Pakistan amid Load-Shedding (news, accessed 2026-10-01)
23. European Commission, Joint Research Centre: PVGIS 5.3, PVcalc, optimal angles, radiation database PVGIS-ERA5 (agency data, accessed 2026-10-01)

Last updated 3 October 2026.