Heating and Cooling Calculator: 4 Options Over 10 Years (RUB)

This calculator compares four ways to supply heating and cooling to one building: a direct-fired absorption chiller-heater, boilers with a centrifugal chiller, boilers with a hot-water absorption chiller, and boilers with packaged air-cooled chillers. It works out annual gas, electricity and water use, capital cost and the 10-year cost of ownership. For the default site, 3,000 kW of heating and 2,300 kW of cooling in St. Petersburg, the best and the worst options are RUB 16.1 million apart over 10 years.

I built it for owner's engineers, design consultants and technical directors who choose a scheme at the concept stage. Hover over or tap any number to see what it is made of. The schemes themselves are covered in Data Center Cooling: 5 Options for 5,000 kW and What Is an Absorption Chiller.

All money is in Russian rubles (RUB) including VAT, as the tariffs and prices behind the model are Russian.

How do I use the calculator?

1. Pick one of eight Russian cities. Average monthly temperatures and the design outdoor temperature fill in automatically.

2. Enter the heating and cooling capacity, indoor temperature, the thresholds at which heating and cooling switch on, the average cooling load, hours per day and days per week.

3. Open "Tariffs and finance" and enter your own gas, electricity, water and grid connection prices. All prices include VAT, as the customer sees them on the invoice.

4. Adjust equipment prices, cooling tower parameters and machine efficiencies if you have your own data.

5. Read the verdict and the option cards, sorted by 10-year cost of ownership.

6. The table "When another option takes the lead" shows the tipping point: the tariff at which the runner-up overtakes the leader.

7. "Save as PDF" exports the result together with all inputs.

What assumptions are built into the model?

The building's demand is the same for all four options; only the way it is met differs.

Heating. For each month, peak load is multiplied by the ratio of (indoor minus monthly average temperature) to (indoor minus design outdoor temperature), then by the hours in the month. Heating runs around the clock in months with an average below 8 °C. The result is divided by the distribution (0.96), control (0.97) and emission (0.98) efficiencies, 0.913 combined.

Cooling. Rated capacity × average load (0.8) × operating hours. Cooling runs in months with an average of 12 °C or more, 10 hours a day, 6 days a week. For St. Petersburg that means June to August, 789 hours a year. Cooling is divided by the same efficiencies.

Wet cooling tower. The heat it rejects is the cooling load plus the energy fed to the machine: cooling × (1 + 1 ÷ COP). Condenser water flow is based on a 5 °C range (32/27 °C), pumps on flow and an 18 m head at 0.72 efficiency, fans on 8.5 W per kW rejected. Make-up including blowdown is 2.1 L/h per kW rejected, and 20% is added to the water price for water treatment.

Gas = heat ÷ boiler (or machine) efficiency ÷ gas calorific value of 9.59 kWh/m³. For the hot-water absorption chiller, summer gas for the generator is added: cooling ÷ 0.72 ÷ boiler efficiency at 90 °C.

10-year cost of ownership = capital cost + each year's operating cost, with tariffs rising 8% a year, discounted to today's money at 18%.

Capital cost = equipment + installation and piping (25% for cooling-tower options, 12% for packaged chillers) + grid connection fee: declared electrical capacity × RUB 36,000 per kW.

Default parameter	Value
Gas	RUB 11.8 per m³ incl. VAT
Electricity	RUB 10.5 per kWh incl. VAT
Water incl. sewerage	RUB 50 per m³ incl. VAT
Direct-fired absorption chiller-heater	cooling COP 1.45 on gas, heating efficiency 0.92; RUB 27,000 per kW
Hot-water absorption chiller, 90/85 °C	COP 0.72; RUB 19,500 per kW
Centrifugal chiller with wet cooling tower	COP 6.0; RUB 25,500 per kW
Packaged air-cooled chiller	COP 3.0; RUB 25,350 per kW
Condensing boiler package	efficiency 1.06 on heating, 0.92 at 90 °C; RUB 4,800 per kW
Wet cooling tower	RUB 2,750 per kW of heat rejected
Absorption chiller auxiliaries	8 W per kW of cooling
Boiler house electrical load	15 kW

The direct-fired chiller-heater is sized for the larger of the heating and cooling loads and needs no boiler house. In the hot-water absorption option the boiler house covers both heating and the generator, so it is also sized for the larger of the two. Price sources are shown on every option card.

What does a worked example look like?

Default site: St. Petersburg, 3,000 kW of heating, 2,300 kW of cooling. Over a year it needs 7,843 MWh of heat and 1,590 MWh of cooling; heating degree-days are 4,374.

The leader is boilers with a hot-water absorption chiller. The boiler house needs 3,194 kW: the absorption generator takes 2,300 ÷ 0.72 = 3,194 kW, more than the heating load. The cooling tower rejects 2,300 × (1 + 1 ÷ 0.72) = 5,494 kW. Equipment costs RUB 75.3 million, installation RUB 18.8 million, the 145 kW grid connection RUB 5.2 million. Total capital cost is RUB 99.3 million.

Annual gas: 771,569 m³ for heating (7,843 MWh ÷ 1.06 ÷ 9.59) and 250,294 m³ for cooling (1,590 MWh ÷ 0.72 ÷ 0.92 ÷ 9.59), RUB 12.1 million in total. Electricity: 178,418 kWh, RUB 1.9 million. Water: 9,099 m³, RUB 0.55 million with treatment. Operating cost is RUB 14.5 million a year.

Option	Capital cost	Operating cost per year	Declared electrical load	10-year ownership
Boilers + hot-water absorption chiller	RUB 99.3M	RUB 14.5M	145 kW	RUB 184.4M
Boilers + centrifugal chiller	RUB 116.8M	RUB 13.4M	453 kW	RUB 195.6M
Direct-fired absorption chiller-heater	RUB 118.1M	RUB 14.0M	97 kW	RUB 200.4M
Boilers + packaged air-cooled chillers	RUB 109.6M	RUB 15.5M	782 kW	RUB 200.5M

The centrifugal chiller is RUB 1.1 million a year cheaper to run but RUB 17.5 million dearer up front, and at an 18% discount rate it does not recover that within 10 years. The calculator shows the tipping points: the centrifugal option takes the lead if gas rises above RUB 19.42 per m³ or electricity falls below RUB 1.23 per kWh.

Climate changes the ranking. With the same inputs, Moscow and Novosibirsk keep the same leader, while in Krasnodar the direct-fired absorption chiller-heater comes first: RUB 196.6 million against RUB 199.6 million for the hot-water absorption option.

What are the limitations?

It compares options; it is not a cost estimate.

• Plant rooms, flues, the gas pipeline and gas supply limits, redundancy, service, repairs and spare parts are not included. They are estimated separately for each site.

• The model runs month by month. Load inside a month is averaged: hot days in May and September do not count as cooling days.

• Machine efficiencies are constant. COP dependence on outdoor temperature and part load, and free cooling, are not modelled.

• The centrifugal chiller price is taken from the nearest equipment class, because such machines are listed only "on request". The hot-water absorption chiller price is an estimate.

• Grid connection rates differ several-fold between Russian regions, and this is exactly where the options diverge most. Enter your own rate.

FAQ

Why does an option with a COP of 0.72 beat a centrifugal chiller with a COP of 6?

Because the comparison is about money over 10 years, not efficiency. The hot-water absorption chiller burns more gas, but the option needs 145 kW of electrical capacity against 453 kW for the centrifugal chiller, and the machine itself is cheaper. It saves RUB 17.5 million up front and loses RUB 1.1 million a year in operation.

What does "10-year cost of ownership" mean?

It is capital cost plus 10 years of operating cost, with each future year discounted to today's money. Tariffs grow 8% a year and the discount rate is 18%; both can be changed in the left panel. What goes into lifetime cost is covered in Chiller Total Cost of Ownership.

Why do packaged chillers lose, even without a cooling tower or water treatment?

A packaged chiller with an air-cooled condenser has a COP of 3.0, half that of the centrifugal chiller. For the default site that means 782 kW of declared capacity, a RUB 28.1 million connection fee and RUB 6.4 million of electricity a year. Savings on the tower and installation do not cover it.

Can I model a site that needs cooling all year round?

Roughly: set the cooling threshold below the coldest monthly average, 24 hours a day, 7 days a week. Free cooling is not modelled; for data centers see Data Center Cooling: 5 Options for 5,000 kW.

Need an exact calculation for your site? Get a consultation