Yes, with the right split of duties. Solar thermal works off-grid almost perfectly — a thermosiphon collector needs no electricity at all. A heat pump runs well off-grid in mild, sunny climates and through spring and autumn, when a modest PV array can carry it; in cold-climate winters, when a 1–3 kW draw would empty a 10 kWh battery in four to six hours, the practical design adds thermal storage and a wood, pellet or LPG backup.
Which parts of a solar heating system need no grid at all?
Solar thermal is the most genuinely off-grid heating technology in common use. A thermosiphon system circulates by density difference alone: no pump, no controller, no electricity, nothing to fail in a power cut. Solimpeks TSM units in the 120–350 litre range are built on exactly that principle, and it is why solar water heating spread across Türkiye and the Mediterranean long before subsidy schemes existed.
A pumped system is only marginally less independent. A solar pump station and differential controller draw roughly 20–60 W, and only when the sun is shining — which means a single small PV module and a 12 V controller can run the whole circuit. A drain-back system adds a further advantage off-grid: if the pump stops, the collectors empty themselves rather than boiling.
Why is a heat pump hard to run off-grid?
Because the load is continuous and arrives when the sun does not. The numbers are unforgiving:
| Requirement | Mild climate | Cold climate |
|---|---|---|
| Annual heat pump electricity | 3,000 – 5,000 kWh | 8,000 – 12,000 kWh |
| PV needed to cover it annually | 2 – 4 kW | 6 – 9 kW |
| Typical winter daily consumption | 8 – 20 kWh | 25 – 60 kWh |
| Usable battery for one winter night | 10 – 15 kWh | 20 – 40 kWh |
Three problems compound. First, seasonal mismatch: heating demand peaks in December, when a northern European array produces perhaps a tenth of its June output. Second, the continuous draw — 1 to 3 kW in cold weather — empties a 10 kWh battery in four to six hours. Third, batteries themselves lose capacity in the cold: usable lithium iron phosphate capacity falls by roughly 10–15% at 0 °C and up to 25% at −10 °C, precisely when demand peaks.
Annual energy balance is therefore the wrong test. An array sized to match annual kWh will still leave a house cold in January.
What actually works off-grid?
The systems that succeed are hybrids that put the seasonal burden on stored fuel and let electricity do the easy months:
- Solar thermal for hot water, year round. The one component that needs nothing from the grid.
- A wood or pellet boiler with a large buffer for deep winter, sized on stored litres rather than kW.
- A heat pump for spring and autumn, when a modest array can genuinely cover it and efficiency is at its best.
- A domestic-hot-water-only heat pump in summer, running from surplus PV at midday and storing the result as hot water rather than as battery charge.
- PVT panels as the heat source, which return both electricity and low-grade heat from the same area — useful when roof space, not budget, is the constraint. See how does a PVT panel work as a heat pump source?
Cold-climate hardware helps at the margins. Solimpeks' Varm Up Series EVI models operate down to −30 °C and reach a COP of up to 4.9 at A7/W35, so shoulder-season performance is strong — but no compressor changes the fact that December sunshine is scarce.
What about "off-grid ready" in a grid-connected home?
This is where the same thinking pays. Maximising self-consumption is now worth more than exporting, and regulation is pushing that way: under a regulation published on 2 April 2026, Türkiye moved non-residential unlicensed producers from monthly to hourly netting from 1 May 2026, with residential subscribers exempt. Under hourly netting, midday electricity that leaves the site earns little, so converting it into hot water in a well-stratified tank is often the highest-value use available.
The practical off-grid rules of thumb: heat is far cheaper to store than electricity, typically by a factor of ten or more per unit of capacity; a buffer tank buys you hours of autonomy for a fraction of a battery's cost; and any off-grid heating design should be sized on the worst week of January, never on the annual total.
Frequently asked questions
Can a heat pump run on solar panels alone?
Across a year the arithmetic works — 6 to 9 kW of PV covers a cold-climate heat pump's annual consumption. Day to day it fails, because December output is a fraction of demand. Grid connection or a fuel-based backup remains necessary.
Does a solar water heater work in a power cut?
A thermosiphon system works normally because it has no electrical components at all. A pumped system stops circulating, and drain-back designs empty the collectors safely; pressurised glycol systems simply stagnate until power returns.
How big a battery do you need to run a heat pump overnight?
Ten to fifteen kWh of usable capacity in a mild climate, and twenty to forty in a cold one, before allowing for the 10–25% capacity loss lithium batteries suffer at low temperatures. That is why cold-climate off-grid designs store surplus as hot water in a buffer tank and keep a fuel backup, rather than relying on batteries alone.
Is it better to store heat or electricity off-grid?
Heat, by a wide margin. A litre of water heated 40 K stores about 46 Wh, and tank storage costs a small fraction of battery storage per kWh. Off-grid systems should convert surplus generation into stored hot water first.