Question 1

Do solar panels pay off in Estonia?

Accepted Answer

Yes, but more slowly than a few years ago. A heat-pump house with 10 kWp of panels (no battery) saved €586 a year over 2025-10 – 2026-09, and the €6,400 investment pays back in 11.0 yrs. The reason is the low sale price: surplus earns the exchange price minus a margin, while buying adds network fees and taxes.

Question 2

How big a battery makes sense?

Accepted Answer

In the default scenario a 10 kWh battery beside the panels adds €821 of saving a year (of which the balancing market €431) and the payback with the panels is 5.4 yrs. Rule of thumb: capacity about one evening and night of consumption (5–15 kWh); on the balancing market power (kW) matters more. Move the slider and watch where the extra saving stops growing.

Question 3

How much does a 10 kWh battery earn on the mFRR/aFRR market?

Accepted Answer

The default scenario’s 10 kWh battery (10 kW inverter) got €381 from activations and €50 from the capacity market a year. A battery alone, without panels, saved €696 a year with the balancing market and arbitrage. The numbers rest on the real activations of one home near Tartu, scaled by inverter power.

Question 4

Does a battery without panels pay off?

Accepted Answer

A battery alone (10 kWh, 10 kW inverter) earned €696 a year from arbitrage, the balancing market and the capacity market, paying back in 4.7 yrs on a €4,150 investment. That depends more on market conditions than on the sun: the price swings and activation prices of winter 2025 may not repeat.

Question 5

South or east–west?

Accepted Answer

A south-facing roof at 30–40° gives the most kWh a year. An east–west layout produces 10–15% less a year but spreads output into the morning and evening, when consumption and prices are higher and the midday surplus smaller. In the calculator each group of panels has its own direction and tilt, so the difference shows at once.

Question 6

What price do I get for surplus?

Accepted Answer

The exchange price minus the seller’s margin, for example 1.8 c/kWh at Enefit: at an exchange price of 100 €/MWh you get €0.08 per kWh, while buying the same kWh on the Võrk 4 day rate costs €0.20. Over 2025-10 – 2026-09 the mean exchange price was 82 €/MWh, and usually below that in sunny hours.

Month	Production	Consumption	Bought	Sold	Balancing	Bill without	Bill with	Saving
Oct 2025	579	909	810	367	€84	€200	-€5	€205
Nov 2025	148	1,146	1,236	182	€51	€261	€160	€101
Dec 2025	54	1,325	1,382	63	€19	€248	€195	€52
Jan 2026	23	2,068	2,297	187	€78	€573	€474	€99
Feb 2026	77	1,898	1,962	86	€33	€539	€456	€83
Mar 2026	1,068	1,125	707	339	€16	€203	€85	€118
Apr 2026	1,328	1,018	474	404	€9	€171	€55	€116
May 2026	1,612	631	193	694	€25	€124	-€6	€131
Jun 2026	1,481	447	174	785	€41	€100	-€42	€142
Jul 2026	1,515	421	244	616	€23	€85	-€13	€98
Aug 2026	1,479	452	177	744	€25	€99	-€29	€128
Sep 2026	1,035	561	301	545	€26	€127	-€7	€134

How much would solar panels and a battery save you?

Result

Month by month

Payback

Annual bill

Where the saving comes from

Energy balance