Solar System Calculator — Checkway Electrotech PH

Load Audit — Appliance Energy & Peak Demand Calculator

ℹ

Fill in your appliances below. The audit calculates: daily kWh, peak running load (kW), and — critically — the surge/inrush peak that must not exceed your inverter's surge rating. Motor loads (AC, pumps, fridge) have high startup current. Click "Apply to Design Inputs" to transfer the results automatically.

When done →

Appliance / Load	Watts (W) Nameplate	Qty	Day hrs	Night hrs	kWh/day w/ DF	Load Type NEC/IEC 61000-3-2	Demand Factor %	Duty % Cycle	PF Power factor	VA Apparent pwr	Inrush × Mult.	Surge W No DF

Daily Energy Summary

Total Daytime Load

0.00

kWh/day

Total Nighttime Load

0.00

kWh/day

Total Daily kWh

0.00

kWh/day

Avg Monthly Bill Est.

₱0

Peak Demand & Inverter Sizing

Running Peak (kW)

0.00

kW

Sum of all loads running at the same time, with demand factor applied.
= Σ (W × qty × duty% × demand factor) — drives inverter continuous rating.

Surge Peak (kW)

0.00

kW

Worst-case millisecond spike when the largest motor starts while everything else is already running.
= Running peak + (Motor inrush W − Motor base running W)
e.g. All loads running (4.12 kW) + Water Pump inrush (2.24 kW) − Pump base (0.19 kW) = 6.17 kW surge

Recommended Inverter

0.00

kW continuous

Minimum continuous rating with 20% safety headroom (NEC 220.97).
= Running peak kW ÷ 0.80
The inverter's surge rating (2.5–3× continuous for LF type) must also exceed the Surge Peak above.

Largest Single Motor Surge

—

= Nameplate W × Qty × Inrush multiplier
This single load drives the surge peak calculation.

Load Classification Guide — NEC Art.220, NEC Art.430, IEC 61000-3-2, IEEE 141

✓ Resistive — 1.0×

PF = 1.0 | No harmonics | No surge

Incandescent bulbs, heating elements, rice cooker, electric stove, water heater, electric iron (steady-state).

⚡ Electronic — 2.0×

PF = 0.85 | THD 10–150% | Inrush 1.5–2×

LED drivers, laptops, TVs, phone chargers, routers, SMPS. Non-linear per IEC 61000-3-2. NOT resistive. Demand factor auto-applies for qty ≥5.

⚠ Light Motor — 3.0×

PF = 0.80 | NEC 430.24: 125% FLA

Ceiling fans, stand fans, washing machines, blenders, power tools. Inrush 2–4×. DF 75% if qty ≥4 (NEC 220.53).

🚨 Heavy Motor — 6.0×

PF = 0.75 | Inrush 4–8× DOL

AC units, ref compressors, water pumps, deep-well pumps, air compressors. DF 65% if qty ≥4 (IEEE 141). Use soft-starter to reduce to 2–3×.

⏱ Short-Duration — 1.0×

PF = 1.0 | NEC 220.60: 50% DF

Loads used <30 min at a time: microwave, kettle, hair dryer, toaster. 50% demand factor for energy; 100% for surge check.

💡 Key insight: LED lights are not resistive — they use switching driver circuits (non-linear loads per IEC 61000-3-2 Class C). TV sets, laptop chargers, phone chargers, and routers are all electronic non-linear loads. Demand Factor is automatically applied per NEC/IEEE: 10 LEDs at 100% DF vs. 20+ LEDs at 50% DF — because not all rooms are occupied simultaneously. The VA column (not W) is what your inverter must actually supply.

Project Information

SINGLE PHASE — Residential / Small Commercial

Project Name

Location / Address

Saved Projects

Peak Sun Hours (PSH) (?)Avg daily solar radiation hours. Philippines: 4.5–5.5 hr/day. Davao Region: ~5.0–5.2 hr/day.

Lowest Expected Temp (°C) (?)Used for NEC 690.7(A) cold-temp Voc safety check. PH lowland typical: 22°C. Tagum: ~22°C.

Mounting Type

Cable Run Distances — Voltage Drop

DC Run Distance (m) (?)One-way distance from array to inverter. Used for DC voltage drop calculation. NEC 690 allows ≤2% VD on DC side.

Array → Inverter (one-way, meters)

AC Run Distance (m) (?)One-way distance from inverter to distribution panel. NEC allows ≤3% VD on AC side.

Inverter → Panel Board (one-way, meters)

System Bus Voltage (V)

Daily Load Profile & Battery Autonomy

Daytime Load (kWh/day)

Energy used during solar hours (~6am–6pm)

Nighttime Load (kWh/day)

Energy used at night — supplied by battery

Battery Sizing Scenario

Sizing Mode (?)Choose how to size your battery. Normal: overnight only. Backup: for grid outages (shares battery with nighttime). Extended: typhoon/bad weather — no sun for multiple days, battery must supply ALL loads.

Critical / Backup Load (kW) (?)Peak power of essential loads during outage. Battery sized for MAX of: nighttime kWh OR backup kW × hours — whichever is larger. They share the same battery.

Lights, fans, fridge, router — essential loads only

Backup Autonomy (hours) (?)Hours of backup from battery. Battery = MAX(nighttime kWh, backup kW × hours). If backup scenario is larger, battery is upsized accordingly.

Battery = MAX(night kWh, backup kW × hrs) — not the sum

Peak Surge Demand — Inverter Sizing

Peak Running Load (kW) (?)Total simultaneous running power of ALL loads at peak — inverter continuous rating requirement. Auto-filled from Load Audit.

All loads ON simultaneously — drives inverter continuous rating

Peak Surge / Inrush Load (kW) (?)Worst-case millisecond surge when the largest motor starts while other loads are already running. Auto-filled from Load Audit.

Inrush when largest motor starts — inverter surge rating must exceed this

💡 LF (Low Frequency) inverters surge at 2–3× continuous — better for motor loads. HF inverters: only 1.5–2×. Always choose LF for systems with AC units or pumps.

System Parameters

System Efficiency (%) 80.0%

Loss Components

Wiring & Cable

2.0%

Inverter Conv.

4.0%

Soiling & Dust

3.0%

Module Mismatch

2.0%

Shading

1.0%

Temperature derating handled separately by Tc Pmax + mount type above.

Battery Depth of Discharge (DoD %)

Battery Round-Trip Efficiency (%)

Tc Voc (%/°C) (?)Temperature coefficient of open-circuit voltage. Auto-filled when you select a panel model. Typical N-Type: -0.25%/°C

Tc Pmax (%/°C)

Inverter Voltage Safety Margin (%)

Recommended: 90–95% of inverter max VDC

Annual Panel Degradation (?)Panels lose output each year. N-Type TOPCon: ~0.40%/yr. P-Type PERC: ~0.55%/yr. By Year 25, output is 90–93% of Year 1. This reduces 25-yr savings by 5–7% vs assuming constant output. 0.50%/yr

0.20% — Premium TOPCon0.55% — Standard PERC1.0% — Old/Budget

Financial Parameters

Monthly Electric Bill (₱)

Non-Offsettable Fixed Charges (₱/mo) (?)Distribution, transmission, metering fees your DISCO charges regardless of solar. NM credits cannot reduce these. Typical PH: ₱700–₱1,200/mo depending on utility.

Meralco ~₱1,100 | NORDECO/Tagum ~₱950 | DLPC/Davao ~₱850 | VECO/Cebu ~₱950

Electricity Rate (₱/kWh)

Annual Rate Escalation (%)

Historical PH average: 4–6%/year

Loan Interest Rate (%/yr)

Preferred Loan Term

📐

Run the calculator to see system design results.

☀PV Array Sizing & String Configuration

Required kWp

—

kWp

Installed kWp

—

kWp

No. of Panels

—

No. of Strings

—

Panels / String

—

Panel Model

—

Panel Wattage

—

Wp

String Voltage — STC (25°C)

String Voc (STC)

—

V

String Vmp (STC)

—

V

Cold-Temp Voc — NEC 690.7(A) Safety

String Voc (Cold)

—

V

% of Inverter Max

—

%

Hot-Temp Vmp — MPPT Range Check

String Vmp (Hot)

—

V

MPPT Status

—

String Configuration

Panels / String

—

No. of Strings

—

Total Panels

—

Array Vmp

—

V

⚡Inverter / Hybrid Inverter

Min Required (kW)

—

kW

peak load + charging + 20%

Selected Rating

—

kW

—

Model

—

Max PV VDC

—

MPPT Range

—

Surge / Inrush Peak

—

kW

Inverter surge rating must exceed this value

🔋Battery Bank

Required Energy

—

kWh

Required Capacity

—

Ah

Model

—

Units (Parallel)

—

Units/String

—

Ah/Unit

—

Total kWh

—

🔌

Run the calculator first to generate the electrical design.

₱

Run the calculator to see the financial analysis.

☀ Total System Cost

—

One-time investment — panels, inverter,
batteries, wiring & installation

💰 Monthly Bill Saved

—

per month vs. your current
bill of —/mo

⏱ Get Your Money Back In

—

years — then electricity
is FREE forever

📈 Total Savings in 25 Years

—

total money back after
recovering system cost

🏦 Earns More Than a Bank

—

yearly growth vs. ~5%
bank time deposit

Bank Financing Options — Adjust & Compare

Down Payment (%)

Loan Term

Interest Rate (%/yr)

Loan Amount

—

Down payment: —

Monthly Savings vs. Monthly Amortization — The Key Question

ℹRun the calculator and adjust financing above to see your monthly comparison.

Full Financing Comparison — All Terms

Term	Down Payment	Loan Amount	Monthly Amort.	Monthly Savings	Monthly Net	Total Interest	Payback

Project Cost Breakdown

Solar Panels
—

Inverter / Hybrid Inverter
—

Battery Bank
—

Racking & Mounting—

Wiring & Protection—

Installation Labor—

Permits & Misc—

Total Project Cost—

Battery Mode Comparison — Cost & Export Impact

How your system cost and export behavior change across the three battery sizing modes. Export happens when the array generates more than daytime load + battery charge needs — the surplus feeds back to the grid.

Run the calculator to see mode comparison.

Environmental Benefits

Annual Energy Generated—

Annual CO₂ Offset—

Equivalent Trees Planted—

25-Year Investment Returns

Monthly Savings (avg)—

Annual Savings (Year 1)—

Simple Payback (cash)—

NPV (25 Years)—

IRR (25 Years)—

25-Year Total Savings—

25-Year Net Profit—

💡Solar vs. Bank Deposit: Even at 7% IRR, solar significantly outperforms a bank time deposit (~5% p.a.) — and your savings grow every year as electricity rates rise.

🔌 Net Metering — Export Excess Energy to the Grid

Earn credits from your electric company for unused solar energy you send back to the grid.

🔌

Run the calculator first, then come back here to explore net metering.

Net Metering Settings

Distribution Utility

Net Metering

Enable Net Metering

Export Rate

—

₱ per kWh exported

Daily Energy Balance — Where Does Your Solar Energy Go?

☀ Solar Generated

—

kWh/day

🏠 Used Daytime

—

kWh/day

🔋 Charges Battery

—

kWh/day

⚡ Exported to Grid

—

kWh/day

🌙 Night from Battery

—

kWh/day

Export Earnings

Energy Exported Daily—

Energy Exported Monthly—

Energy Exported Yearly—

Export Rate (₱/kWh — generation credit)—

Monthly Bill Credit (export)—

Annual Bill Credit (export)—

Estimated Remaining Monthly Bill —

⚠ Fixed charges (₱900/mo) cannot be offset by NM credits — this is your minimum bill regardless of system size.

Impact on Your Bill & Investment

Monthly Savings (self-consumption)—

Monthly Bill Credit (NM export)—

Estimated Remaining Bill—

Bill Reduction—

Payback Period—

25-yr Net Profit—

Philippine Net Metering — What You Need to Know

📋 Legal Basis

Governed by ERC Order No. 2009-12-0013-SC and Republic Act 9513 (Renewable Energy Act of 2008). All distribution utilities are mandated to accept net metering applications.

⚡ System Size Limit

Net metering is available for systems up to 100 kW — covers virtually all residential and small commercial systems.

💡 How Credits Work

Excess energy exported is credited at the blended generation charge of your utility. Credits appear on your monthly bill and reduce what you owe. If credits exceed your bill, the surplus rolls over to next month.

🔧 What You Need

A grid-tie or hybrid inverter, a bi-directional meter (installed by your utility), and a net metering agreement with your distribution utility.

ℹSelect specific brands and models. The calculator validates string voltages against the selected inverter. Click Apply & Recalculate after choosing.

Solar Panels

Brand

Model

Inverter / Hybrid

Brand

Model

Battery

Brand

Model

📄

Run the calculator to generate the report.

🏷 Your Details on Quotation (replaces "Checkway Electrotech PH" on client copy)

Name / Company

Phone / Mobile

Address

Website / Email

⭐ Pro: your name, phone & address appears on the quotation header — Checkway branding is removed. 🏢 Business: add your company logo on top of that.

💰 Markup / Selling Price

Set your profit margin per line item. Client sees selling price — cost is never shown.

% global

☀ Solar Panels

% —

⚡ Inverter

% —

🔋 Battery Bank

% —

🔩 Racking & Cabling

% —

🔧 Labor & Commissioning

% —

📋 Permits & Misc

% —

Your Cost

—

Client Price

—

Gross Profit

—

Gross Margin

—

🔒 Cost prices never
appear on client quotation

📝 Terms & Conditions (printed on quotation — edit to match your business)

Valid for

days from date of quotation

Show performance disclaimer (±15–20% output variation note) Show engineering standard (NEC/IEEE/PEC reference)

🔐

Admin Access

This section is for Checkway Electrotech staff only. Enter your admin password to manage the equipment database and view formulas.

✓Admin mode active — Checkway Electrotech equipment database management panel.

🧪Tier Test Mode

Switch license tier to test how the calculator behaves for each tier. Reloads the page to apply. Settings are for this browser session only — does not affect the actual license file.

Current: trial

Lead Gate: checking… — clears captured flag so email form shows again on next Calculate

#	Brand	Model	Tech	Wp	Voc	Vmp	Isc	Tc Voc	Price ₱	Actions

Engineering Formulas — Admin Reference (Not visible to customers)

✓Validated against NEC Article 690, IEEE 1562, and Mayfield Renewables engineering standards.

1. PV Array Sizing (Combined Method)

// Battery energy needed — depends on selected mode E_battery = MAX(Night_kWh, Backup_kW×Hrs) // Mode: Night+Backup E_battery = (Day_kWh + Night_kWh) × Days // Mode: Extended Autonomy // PV must also recharge the battery each day: Battery_charge_kWh = E_battery / Batt_RT_eff // Total array daily output required (IEEE 1562 combined method) Total_array_kWh = Day_kWh + Battery_charge_kWh // Temperature derating — cell temp rises above ambient in PH heat T_cell = T_ambient(35°C) + Mount_adder(25–35°C) P_derate = 1 + (Tc_Pmax/100) × (T_cell − 25) // < 1.0 in hot climate // Required kWp — array must be LARGER to compensate for heat loss Required_kWp = Total_array_kWh / (PSH × η × P_derate)

2. NEC 690.7(A) Cold-Temp Voc Check

// Per NEC 690.7(A)(1) — Tc method (accurate) CorrFactor = 1 + (Tc_Voc/100) × (T_cold − 25) Voc_cold_per_panel = Voc_STC × CorrFactor String_Voc_cold = N_panels × Voc_cold_per_panel // MUST be ≤ Inverter_Max_VDC × safety_margin Max_panels = FLOOR(Inv_Vmax × margin / Voc_cold)

3. Battery Bank Sizing — Three Modes (IEEE 1013 / IEEE 1562)

// MODE 1: Night Only (grid-tied, daily cycling) E_battery = Night_kWh // MODE 2: Night + Backup (hybrid/off-grid) // Backup runs from SAME battery — size for the LARGER scenario: E_battery = MAX(Night_kWh, Backup_kW × Backup_hrs) // MODE 3: Extended Autonomy — Typhoon/Bad Weather (IEEE 1562 §5.3) // No solar for N days. Battery supplies ALL loads — day AND night: E_battery = (Day_kWh + Night_kWh) × Days_of_Autonomy // Philippines typical: 2 days for standard, 3 days for critical // Ah sizing (all modes) — IEEE 1013 formula: Required_Ah = (E_battery × 1000) / (sysV × DoD × Inv_disch_eff) // Inv_disch_eff ≈ 0.93 (DC→AC conversion loss from battery) Bank_config: blocks_series = sysV / block_V strings_parallel = CEIL(Required_Ah / block_Ah)

4. Financial — NPV & IRR

NPV = Σ(t=1→25)[Savings_t/(1+r)^t] − Cost Savings_t = kWh×Rate×(1+escalation)^(t-1) // IRR: Newton-Raphson iteration solving NPV=0 Payback = Total_Cost / Annual_Savings

5. String Voltage Analysis — Live Calculated Values (NEC 690.7)

Run the calculator to populate with live values.

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