What a year of solar and batteries saved us in 2025

Original Article ↗ Hacker News Discussion ↗

Household Energy Use & Lifestyle Differences

  • Many commenters focus on the very high annual consumption (~17–21 MWh) and compare it to their own (often 6–13 MWh, sometimes far less).
  • Suggested drivers: two EVs, a hot tub, server rack/homelab, both adults working from home, and likely electric heating/hot water and cooking.
  • Several people note that per‑household averages are misleading: square footage, climate, insulation, appliance vintage, and lifestyle can easily create 2–3× variation.
  • Some argue the author would get a better return investing first in efficiency (insulation, efficient heating, appliance upgrades) before piling on solar and batteries; Jevons paradox is mentioned (cheaper energy leading to higher use).

Solar + Batteries, Tariffs, and Arbitrage

  • A lot of discussion centers on UK time‑of‑use tariffs and the ability to charge batteries cheaply overnight and export at higher daytime rates.
  • Some are surprised this arbitrage is allowed; others say it’s actively beneficial as decentralized storage that smooths demand peaks.
  • UK export caps and specialist tariffs (e.g., Octopus variants) are discussed as key to making the economics work; without such tariffs, payback would be worse.
  • People from other regions (California, parts of Europe, Sweden) report very different economics because of fixed grid charges, net-metering changes, or negative wholesale prices at midday.

Battery Technologies, Pricing, and DIY vs Turnkey

  • Powerwalls are widely criticized as expensive compared with:
    • BYD and other rack batteries,
    • EVs used as storage (V2L/V2G/V2H),
    • DIY LFP banks plus hybrid inverters.
  • Counterpoints: Powerwalls include inverters, have strong surge capability, are integrated/“appliance-like,” and come with mainstream support.
  • Several describe DIY systems with Chinese batteries and inverters at near €100/kWh, but emphasize:
    • terrible documentation and protocol reverse‑engineering,
    • safety/insurance and code‑compliance risks,
    • quality differences between cheap and tier‑1 gear.

Heat Pumps, Efficiency, and Comfort

  • Big side-thread on heat pumps:
    • One camp calls them “gimmicks” or overly complex, preferring insulation and simple resistive heating when self‑sufficient on solar.
    • Others stress that heat pumps are mature, highly efficient, no more fragile than air conditioners, and often the best way to cut total energy use.
  • Air‑to‑air vs geothermal, lifespan, maintenance, and comfort (air vs radiant heating) are debated; consensus: start with building envelope, then consider heat pumps.

Payback, Investment Framing, and Non‑Financial Value

  • The quoted 9–11 year payback is viewed by many as “not bad,” especially with rising electricity prices and long panel lifetimes.
  • Others argue that, once you discount future savings and include replacement/maintenance (batteries, inverters, roof work), broad stock or bond investments still dominate purely financially.
  • Backup power during outages and partial energy independence are framed as major intangible benefits that can justify a marginal or even slightly worse monetary return.

Scaling, Grid-Level and Policy Concerns

  • Some warn that residential solar+batteries don’t scale to multi‑week, country‑level storage needs; Sweden is cited as an example where seasonal deficits make batteries insufficient.
  • Others respond that:
    • residential storage helps the grid today (peak shaving, local buffering),
    • large-scale batteries and pumped hydro will handle grid balancing,
    • future battery production and falling prices could change the calculus substantially.
  • Concerns about rooftop-solar “scams” (especially in Texas), small sub‑optimal arrays, and aggressive sales channels appear; co‑ops, ground‑mounts, and carports are suggested as better deployment models in many cases.