Solar Water Heating: Costs, Sizing & Savings

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Estimation Tool — Not Engineering Advice

This calculator provides indicative figures for domestic solar water heating feasibility. Actual savings, system sizing, and costs will vary based on local conditions, installer quotes, and usage patterns. Consult a qualified solar engineer before making investment decisions.

Electricity tariff data sourced from GlobalPetrolPrices.com (Q4 2025) · Solar radiation from Global Solar Atlas by the World Bank · Construction costs based on regional market estimates.

Project Details

Location (city) ?

Selecting a city auto-fills solar radiation, collector type, inlet temperature, electricity rate, and currency. All fields remain editable.

Number of People

⚠ Unusually high — please verify

Units · Metric: L, °C

Adjust pre-filled values

Edit hot water demand, solar system, costs, loan and more

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Hot Water Demand

60 L/person · 60°C tank storage

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Daily Hot Water per Person ?

Standard residential benchmark is 60 litres per person per day per WHO and ASHRAE guidelines.

L/day

Standard: 60 L/person/day

Inlet Water Temp (°C) ?

Cold water supply temperature entering the system. Auto-estimated by region — adjust with local data if available.

Tank Storage Temp (°C) ?

60°C is the standard tank temperature to prevent Legionella growth. A thermostatic mixing valve (TMV) blends stored hot water with cold to deliver safe 50°C at the tap. Do not set below 60°C.

60°C tank · TMV delivers 50°C at tap

⚠ Below 60°C risks Legionella growth — 60°C is the recommended minimum

Fuel / Energy Type ?

The energy source of your conventional backup water heater. Selecting a fuel type auto-fills the heater efficiency and sets the correct unit for fuel price.

Backup Heater Efficiency ?

Electric resistance heater: 100%. Gas boiler: ~88%. Heat pump: 250–350%. Auto-filled based on fuel type — override with actual value if known.

100% = electric resistance heater (most common)

Solar System

Glazed flat plate · 60% efficiency · 60% solar fraction

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Collector Type ?

Auto-recommended by city climate. Glazed flat plate: best for warm/sunny climates (GCC, Africa, Americas). Evacuated tube: better performance in cold/cloudy climates (Europe).

Gross Area per Collector (m²) ?

Total surface area of one collector facing the sun, including frame. Auto-filled by collector type. Override with your panel's spec sheet value.

autoBy collector type · override with spec sheet

Aperture Area per Collector (m²) ?

Effective area through which solar radiation enters. Auto-calculated from gross area and collector type. Override with spec sheet value if available.

autoFrom gross area · override with spec sheet

Collector Efficiency ?

Fraction of incoming solar energy converted to heat. Glazed flat plate: ~60%. Evacuated tube: ~70%. Unglazed: ~45%. Override with manufacturer's rated value.

autoBy collector type · override if known

Pipeline & Tank Losses ?

Heat lost in pipes and storage tank. Typical range: 10–25%. 20% represents a standard residential installation.

Typical range: 10–25% · Use 20% for standard installations

Solar Contribution Ratio ?

Fraction of total heating load delivered by solar. 60% is the standard feasibility benchmark (IEA, ASHRAE). GCC/high radiation: up to 80%. Europe/low radiation: 40–50%. Avoid exceeding 80% — causes summer overheating and stagnation.

Standard: 60% · GCC up to 80% · Europe 40–50%

⚠ Above 80% may cause summer overheating and stagnation

Financial Settings

AED · Electric · 1% maintenance · 20yr lifetime

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Currency

Fuel Price (AED/kWh) ?

Cost per unit of fuel for your backup heater. Auto-filled for electricity from city data. For gas/LPG/diesel enter your local tariff. The tool converts to kWh equivalent automatically.

AED

Annual Fuel Price Increase ?

Expected annual escalation in fuel prices. Higher escalation increases the value of solar savings over time.

%/yr

System Cost per m² gross area ?

Indicative installed cost per m² of gross collector area, including collectors, storage tank, pumps, controller, and labour. Auto-estimated by collector type and currency. Always get a local installer quote for accuracy.

AED

autoIndicative — get a local installer quote

System Lifetime ?

Expected operational life of the solar system. Collectors: 20–25 years. Well-maintained systems in dry climates (GCC) can reach 25+ years. Industry baseline: 20 years.

yrs

First Year Maintenance ?

Annual maintenance cost as a percentage of total system capital cost. Typically 1–2% for domestic systems.

Annual Maintenance Increase

%/yr

Loan (Optional)

No loan — cash purchase

Loan Period (years)

Interest Rate

Down Payment

Estimated Annual Loan Payment —

Discounted Cash Flow (DCF)

Apply discount rate to calculate net present value

Applies a discount rate to future cash flows to calculate net present value (NPV). Useful for comparing solar against other investments. Use your bank's deposit interest rate as a proxy.

Discount Rate

Select a city and enter number of people to get your estimate

System Sizing

Number of Collectors

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Recommended Tank Size

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1.2× daily demand

Total Installed Area

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Daily Hot Water Volume

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First Year Energy Savings

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Required Aperture Area

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Annual Backup Heater Consumption (after solar contribution) —

Financial Summary

LIFETIME NET SAVINGS

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Total System Cost

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capital investment

Total Lifetime Savings

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nominal fuel savings

Break-even Year

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simple payback period

Simple ROI

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lifetime return on investment

Environmental Impact

🌍

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CO₂ avoided

🌳

—

Trees equivalent

🚗

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Car driving avoided

✈️

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Flights offset

Based on grid emission factor of 0.45 kg CO₂/kWh (electric). Tree absorption ~21 kg CO₂/year. Car avg 0.21 kg CO₂/km. Flight avg 0.255 t CO₂/passenger (short-haul).

Cumulative Cash Flow

Nominal