Payback time of the boiler

In comparison:

  • Tesla Powerwall battery. The electricity storage of the household.
    Charged with solar panel or wind or other electricity 
  • traditional 500 litre boiler.
    Charged with solar heat or wind or other electricity 
  • Solixi boiler 1 MWh.
    Charged with Solixi solar concentrator or wind or other electricity

Multiple Tesla Powerwall batteries can be installed. Water boilers and Solixi boilers come also in various sizes.

Need for space, weight

  • Tesla battery: 1 m2 wall with roof, 100 kg
  • 500 l boiler: 1 m2 indoor space, 700 kg
  • Solixi boiler: 8 m2, 16.000 kg, Outside of the house in an insulated hut:

1 MWh is a three-part water tank holding 13,500 litres. Diameter 2.3 metres, height 4m.
0,5MWh, 6,500 litres 2,3×2,3x2m + insulated hut.
6MWh ja 15MWh models are based on modified tank containers.


Approximations including VAT

  • Tesla battery: 571 €/kWh
    (price 4.000€/capacity 7kWh)
  • 500 l boiler: 100 €/kWh
    (price 2.000€/capacity 20kWh)
  • Solixi boiler: 15 €/kWh
    (price 15.000€/capacity 1.000kWh)

The value of stored energy per charge, total value in a year 

Energy price assumption 0.1 €/kWh, 100 full charges in a year

  • Tesla battery: 0,7 €, 70 €
  • 500 l boiler: 2 €, 200 €
  • Solixi boiler: 100 €, 10.000 €

Payback time

100 full charges in a year, 50 % savings from storing energy

  • Tesla battery: 114 years
  • 500 l boiler: 20 years
  • Solixi boiler: 3 years

After the system has been paid for, the storage is practically free, as are wind and solar.

Other considerations

  • Tesla’s battery has a warranty of 10 years, with slowly diminishing capacity.
  • Water boilers last usually for decades, no changes in capacity.
  • Solixi boiler produces and stores cold as well, for air conditioning and heat recovery appliances.
  • Electricity (from renewables for example) can be turned to heat with an affordable and available solutions from electrical resistors to heat pumps, which offer great efficiency.



Solar energy paypack times

  • Suvilahti: 21,8 years
  • Solixi C46: 5,3 years
  • Solixi C99: 3,3 years

In comparison

  • Suvilahti Helsinki, One of the largest solar powerplants in Finland, PV-panels lie on the flat roof in almost horizontal position
  • Solixi solar concentrator produces heat; model C46 is meant for block of flats, larger model C99 is meant for industry and power plants.

Installation area on the roof

  • Suvilahti: 3.000m2, height 0,5m
  • C46: 50m2, height 6m
  • C99: 150m2, height 13m

Surface area, investment

  • Suvil: 2.454m2 (1194 PV-panels 2,1m2), 600.000€
  • C46: 60m2 (6 kpl 10m2 turning mirrors), 18.500€
  • C99: 203m2 (9 kpl 22,5m2 turning mirrors), 39.000€

28.10.2015: power at 14.00, day production

Radiation 1000W/m2, sun height 10 degrees. 8h of bright sunshine.

  • Suvil: 10 kW, 272 kWh
  • C46: 40 kW, 320 kWh
  • C99: 136 kW, 1088 kWh

Suvilahti 28.10.2015

C99 annual production 119 MWh/month

Paypack time

Investment / annual production * price of energy

  • Suvilahti: 21,8 years
  • Solixi C46: 5,3 years
  • Solixi C99: 3,3 years

After equipment has been paid for, the solar energy will be practically free.

Other considerations

Suvilahti produces grid electricity;

  • Transfer-costs, taxes and interest rates can increase paybacktime 2 to 4 fold
  • No energy storage included
  • Roughly 75% of production happens during five summer months
  • Roughly 90% of energy consumption needs to be produced with something else (coal, natural gas, nuclear, hydro etc.)
  • Subsidized energy production
  • The ”traditional” solution to get solar energy

C46 and C99 store energy to an innovative water boiler;

  • No taxes, no transfer fees
  • Energy supplied more evenly around the day and around the year
  • Enables the use of various cost-effective heat recovery -systems
  • Removes the need to buy energy when prices are high, bringing average costs down
  • Enables cooling as well
  • No subsidies for energy

Savings immediately

Solixi lowers energy costs and brings savings immediately, when the investment is financed with a suitable length loan.

Almost free energy

When the loan has been paid, after the payback period, the energy costs collapse another time. Only Solixi service charge remains and a little of the cheapest grid electricity or other bought energy. Free energy, free energy storage, cheap controls and support.

Solar concentrator is profitable alone and so is boiler, but best savings and benefits can be gotten when they function together.

Usually Solixi does not need subsidies to be profitable, but of course they have an impact in a competitive situation. Burning is still subsidized in many different ways and its costs are outsourced to the atmosphere, but maybe not for a long time anymore.


Economies of scale with the system

By sharing and networking solar concentrators, boilers and devices and by common Solixi-powerplants and devices of the housing companies and parts of the city, considerable economies of scale can be achieved and the profitability can be improved even more.